ECHNOLOGY - VIDEO - STEREO - COMPUTERS - SERVI UILD THIS DRAM TESTER „ OR LESS THAN £60! ' KV 1 volt eter mining whether our dynaTnte^ tAM chips are jnctioning properly nd at the rated. peed. 'UILD THE HONE-CO Jse your telephones as a lome intercom/system. UILD A PULSE ^L\ ENERATOR Jur handheld Pulse-IVfate Is i handy troubleshooting -tool, WITCHING EGULATORS i he heart of switching,'' >ower supplies. /' / C-BASEDTEST ff — QUIPMENT :xperimenting with the osic concepts. ^ G ■OH^Ve ^ — \ $2.95 U.S. S3.75 CAN GERNSBACK xxx***xx CAR-RT SORT xx CRQ3 75D456HRR5165M093 D5 05 SEP 91 RE FLUKE AND PHILIPS - THE GLOBAL ALLIANCE IN TEST & MEASUREMENT FLUKE 73 FLUKE 75 m- tlt9" MfcglDUttlfeptft »Jliio»1>olal|jBtiU( Vote, ohms TO flUMdl rtooe lest axuncj ax»+ row baise* i We rM loorh heedl diode lei Oi* basic * accuracy AuoKrie conlJftjity 3- year warranty AutcrmgcAange hold 2M0+ how bartwviirt SyearwaiiaiTly ■Sugo«twU.S Istorra FLUKE 77 PHILIPS More than two million users agree: the Fluke 70 Series handheld digital multimeters are amply the best. These originals have become classics. And the reasons are simple. They are accurate and easy to use. Features made popular by the 70 Series-like fast autoranging, continuity beeper, and quick diode test-are now standards in the industry. Other 70 Series features stand alone. Touch Hold®, for example, locks the reading on the display and signals you with a beep. So you can keep your eyes on the circuit and probes. The 70 Series are built without compromise. All current ranges are fully fused. The resistance function is overload protected to 500V. No detail has been overlooked in making these rugged and reliable meters the first choice of two million professionals. Made in the USA using state-of-the-art man- ufacturing methods, every Fluke 70 Series multimeter is backed by a 3-year warranty. Another first in the industry. Choosing the best handheld multimeter is very simple. Pick up the Fluke 70 Series at your Fluke distributor today. Or call 1-800-44-FLUKE, exl33, for a free brochure. John Fluke Mlg. Co.. Inc. P.O. Box 9090, Everett. WA 98206- J.S.: (206) 356-5400. Canada: (116) 890-7600. Other countries: [206) 356-5500 © 1990 John Fluke Mfg. Co.. Inc. All rights reserved Ad.r»,O7O1-F70 FROM THE WORLD LEADER IN DIGITAL MULTIMETERS. FLUK CIRCLE 121 ON FHEE INFORMATION CARD ay 1991 Vol. 62 No. 5 33 DRAM TESTER Build an under-$60 DRAM unit that performs dynamic-RAM function, speed, and margin tests. Fred Hufft 41 PULSE-MATE Our Inexpensive single-shot and continuous-pulse generator offers positive and negative pulses. David Plant 44 USE YOUR TELEPHONES AS A HOME INTERCOM SYSTEM It's easy to do with our controller board and alert modules! Frank Polimene 56 EXPERIMENTING WITH PC-BASED TEST EQUIPMENT Build your own low-cost PC- based test equipment. James J. Barbarello 49 INSIDE SWITCHING POWER SUPPLIES Learn some applications of, and basic troubleshooting techniques for, two switching regulator IC families. Harry L. Trietely 61 PERSONAL COMMUNICATION NETWORK Can PCN microcell technology make affordable mobile communications a reality? Roger P. Newell I 6 VIDEO NEWS What's new in this fast- changing field. David Lachenbruch 65 HARDWARE HACKER More on toner-cartridge reloading and Santa Claus machines! Don Lancaster 72 AUDIO UPDATE Audio Amplifiers: Do they sound different? Larry Klein 75 DRAWING BOARD A simple, inexpensive logic probe. Robert Grossblatt 77 COMPUTER CONNECTIONS Video standards. Jeff Holtzman PULSE-MATE "'""*"" — *"— nn Wj i ~^B PAGE 41 TELEPHONES AS A HOME INTERCOM SYSTEM ^ ^srpa==3 =^r=n=; invM^ 'spS=5=|pg| I fcmri \\* + §fe";'=H SSjSHgs: [S***~ --.*■■■. Vjmj ILiiJJiSii PAGE 44 V' N I , ^ikpB 96 Advertising and Sales Offices 96 Advertising Index 12 Ask RE 14 Letters 84 Market Center 28 New Lit 22 New Products 4 What's News 50A RE-Shopper* i "Included in selected issues only. to o z o DC o w < If you've ever had to expand your PC's RAM capacity, troubles hoot a memory problem, or upgrade the cy- cle speed of a memory band, you've had the need for a dynamic RAM (DRAM) tester like the one featured on page 33. Our DRAM tester pro- vides an easy method of function testing and measuring the speed (access time) of DRAM IC's, You could spend anything from $150 to $1 000 to buy a DRAM tester. Or you could build ourmultifunction unit — which can function test, accurately test speed, and automatically cycle the tests under high-, low-, or nor- mal-voltage margins — for less than $60! COMING NEXT MONTH THE JUNE ISSUE GOES ON SALE MAY 7. BUILD A 50-MHZ LOGIC ANALYZER Portable unit with its own LCD, can also be interfaced to your PC. BUILD AN ELECTRONIC COMPASS A Hall-effect sensor shows you the way. VOLTAGE-TO-FREQUENCY CONVERTERS How to use them in your designs. PC BASED TEST EQUIPMENT More experiments teach the basics of PC-based test equipment. A* a service to readers. RADIO-ELECTRONICS publishes available plans or information relating to newsworthy products, techniques and scientific and technological developments. Because of possible variances in the quality and condition of materials and workmanship used by readers. RADIO -ELECTRONICS disclaims any responsibility for the safe and proper functioning of reader-built projects based upon or from plans or information published in this magazine. Since some of the equipment and circuitry described in HADIO-ELECTRQNICS may relate to or be covered by U.S. patents, RADIO-ELECTRONICS disclaims any liability for th a infringement of such patents by the making, using, or selling of any such equipment or circuitry, and suggests that anyone interested in such projects consult a patent attorney. RADIO-ELECTRONICS. (ISSN 0033-7862) May 1991. Published monthly by Gemsback Publications, Inc., 500- B Si-County Boulevard, Farmingdale, NY 1 1 735 Second-Class Postage paid atFarmingdale, NY and additional mailing offices. Second-Class mail registration No. 9242. authorized at Toronto. Canada. One-year subscription rate USA. and possessions $17.97. Canada S25.65 (includes G.S.T. Canadian Goods and Services Tax Registration No. R1351662SO), all other countries $26.97 All subscription orders payable in U.S.A. funds only, via international postal money order or check drawn on a USA bank. Single copies $2-95- & 1991 by Gemsback Publications. Inc. All rights reserved. Printed in U.SA POSTMASTER: Please send address changes to fiADIO-ELECTRONICS, Subscription DepL, Box 55115, Boulder, CO 80321-5115. A stamped self-addressed envelope must accompany all submitted manuscripts and/or artwork or photographs if their return is desired should they be rejected. We disclaim any responsibility for the less or damage of manuscripts end/or artwork or photographs while in our possession or otherwise. firf?i- HAJtfWCCK of naK5CCH>irji3i j HnmncMo A yttf a* -*sas 31 DIP SI 9. 95 SD049PS15.9S UHUHllMttf Building I I ibraries O m 3656P 517.95 541 flP 526.95 Counts ■■ 2 3- 3ZS3 $28.95 Count* *t 2 341 5P 521.95 3BEME What's new in the fast-changing video industry. • Low-cost captions. In a hurry- up effort to implement the recent Congressional mandate to include closed-caption decoders in all TV sets 13 inches and larger (Radio- Electronics, October 1990), a spe- cial Electronics Industries Associa- tion (EIA) task force recommended new parameters that would make de- coders inexpensive by building upon the on-screen character-generation systems already used in many sets. The EIA plan, which would decipher existing closed captions for the hear- ing impaired, formed the basis for an FCC rule-making proposal. Members of the task force said the proposed system might add $2 or $3 to the cost of a TV set. The EIA plan envisions certain compromises, making some cur- rently mandatory aspects of caption decoding optional. Those include a special full-screen "text" mode that isn't widely used at present, a second data channel, and captions in color. In exchange, the EIA proposes that Field 2 of Line 21 of the vertical blank- ing interval be opened up for a bet- ter — but optional — second channel, and that the captions be capable of location anywhere on the screen to avoid interference with material in the picture. The proposal was approved by all members of the EIA task force except the National Captioning Institute, which said its own system, currently in use, could also come down to the $2-$3 level when chips are available in large quantities from a variety of sources. The EIA plan possibly can be combined with another EIA project being explored by receiver- and cable- engineering interests. That is a stan- dardized "program identification sys- tem," which would make possible on- screen labeling of station call letters and program titles, along with such information as the running time of the program and how much more remains to be shown, at the push of a remote- control button. Ultimately, such infor- mation could be combined with auto- matically recording VCR's, to tape programs of specific interest — -for ex- ample, all non-scheduled news bul- letins, or all operas. The FCC was ordered by Con- gress to promulgate final closed-cap- tioning rules by April 12. New TV sets made or imported on July 1, 1993 or later must include caption de- coders — but some manufacturers are expected to add the decoders to their sets some time this year if the simplified ElA-proposed rules are adopted. • Digital HDTV. As in audio, "dig- ital" has become the magic word in high-definition TV systems. Most contenders for consideration as the American system now have shifted to digital systems, although detailed en- gineering plans still are scanty. Major digital systems now include those un- der development by the ACTV Con- sortium, consisting of Thomson, Philips, NBC, and the Sarnoff Re- search Center; the Zenith— AT&T combine; and General Instrument. In the latest development, the MIT team, which had proposed an analog system, is working with General In- strument on a combined digital tech- nology. There are some dissenting voices in the digital race, however. Dr. William Schreiber, formerly of MIT and a longtime TV authority who in the past has questioned the consum- er benefits of HDTV, has decried the "stampede" to digital systems at a time when digital transmission hasn't been proven practical. He warned that if all American proposals are dig- ital and digital transmission proves impractical, the 20-year-old Japanese system could be the winner in the U.S. by default. • Interactive video. The FCC has started a rule-making procedure to set aside frequencies for "interactive video data service" C1VDS), which could be used for pay-per-view sys- tems, home shopping, games, edu- cational programming, and even for programming VCR's. The Commis- sion proposes to allocate 500 kHz in the 218-MHz band to IVDS, and to license two operators in each service area to share in this service from home to TV station or cable system. One interactive proponent said that such a system could probably oper- ate much like cellular phone net- works, each cell site connecting up to 10.000 homes by radio and being ca- pable of handling up to 600,000 mes- sages per minute. • Multimedia Computing. What is claimed to be the first mass-market computer with interactive multimedia capability will be manufactured by Emerson Technologies for Trac. At- lanta, and designed to sell for less than $2,000. The price breakthrough, according to Emerson, is the result of the availability of the "PC Video" chip developed by Chips & Technologies Inc.. San Jose, CA. That single-chip processor permits PC's to accom- modate input from VCR's, camcor- ders, TV sets, laser discs, and other video sources, for display on the monitor and storage in the PC's pro- gram. It will even let computer oper- ators watch and listen to on-screen newscasts while involved in other- wise serious labor. The PC Video chip initially is priced at $55 in volume and is claimed to reduce the cost of adding multimedia to computers by as much as 70%. • Instant Video. Ycu may not want to see a full-length movie in 15 sec- onds, but Explore Technology, of Phoenix. AZ. , thinks that's all the time that's needed to transmit it. Explore is proposing a pay-per-view system, based on its patent for data compres- sion, which permits transmission of programming in short bursts to a re- ceiver which stores the information briefly in memory, and then plays it back with the proper timing. Explore says the saving in transmission costs will make such programs competitive with video rentals. The system is said to be compatible with any transmis- sion medium, and includes a trans- mitter and receiver that can be connected by fiber, satellite, broad- cast, coaxial cable, or even phone lines. R-E Now, Testing 68000/386SX Microprocessors Is A Snap. Nothing'? foster than the chips being ; developed today, and nothing's slower than hand wiring or trying to analyze these high- ^ ^ density, surface mounted quad flat pack (QFP) devices for test. No worry, Pomona has the answer. You can choose Pomona's 571 1 SMT Test Clip to grab onto all 132 pins of a Motorola 68020 or 68030, or the 5713, to simultaneously access all 100 pins of an Intel 80386SX. Immediately, your interface with logic analyz- ers, on-line circuit test systems, or lab instruments will be faster, easier, and reliable. A locking mechanism firmly holds the glass-filled, Nylon insulated clip onto the device, making positive contact with each of the IC's gull-wing leads via specially configured, gold-plated, beryllium copper pins. Above, multi-rows of gold-plated phosphor-bronze pins provide an easy-to-access pattern. Suddenly, interface problems are solved. FREE 1991 POMONA CATALOG! l-10-pages of * newest prod 'nets and a», thousands of test solutions. 5515A PLCC Clip Kit contains seven Pomona QuatP Clip Adapter from 20-84 pins. If you anticipate testing various pin- count PLCC or SOIC devices, Pomona's Test Clip Kits will make testing faster too. And, to make the interface between your test clip and logic analyzer sockets or emulator pods easier, Pomona's Flying Leads are available in low-cost packs, or sup- plied with the 5711 and 5713 Test Clips as kits. Of course, all of Pomona's other SMT test accessories are ready to make your IC testing faster and leSS " ^ Color-coded Flying Leads amplify expensive interconnections between PLCC or SOIC lest clip and * „ ' logic analyzer sockets or emulator pods; 3 inches 'long, with oCe yOUl" female socket one end to . 79 dia. pin. Authorized Pomona 25 to&.pirp&k Distributor or contact POMONA ELECTRONICS, 1500 E. Ninth St., P.O. Box 2767, Pomona, CA 91769. (714) 623-3463. FAX (714) 629-3317. ■&1& Nylon is a registered trader™* of DuPont CIRCLE 101 ON FREE INFORMATION CARD ITT Pomona AN ITT EMC WORLDWLDE COMPANY Discover our strengths. What's yoi Analyzing TV and complex video signals? Testing telecommunications signals? Uncovering elusive glitches? CHI 1U i, Zp, J. 56 u UE»I *fi !.»• U Itftnt CM. tall Finding aberrations buried within a signal? You can't depend on banner specs alone to solve problems like these. Whether you're trying to measure waveform parameters or analyze long data streams, identify infrequent events or track down glitches as narrow as 2 ns — there's all the difference between the depth of Tek troubleshooting and the trade-offs in other DSOs that compromise your results. Spec for spec, feature for feature, no other company offers the credentials Tek does to Capturing single-shot events? H 2e«|ii 3.72 U7 UEK «F1 1.6(1 V Zttpi AC4UKE I 32 ttftl SKUE OH Automatic PASS/FAIL testing? effectively match DSO performance to you application needs. Whatever your criteria, you'll find a perfect solution in our line of problem-solving portable DSOs, from 10 to 500MS/S. Select the features to support your application. Tek DSOs offer a diverse set of capabilities including peak detect to uncover elusive glitches. Fast update rate fc live signal display. Combined analog/digits operation for real-time verification of your Copyright e 1990. Tekronii. Inc. AH rigliis reserved. BOB-125 problem? Characterizing signal noise 1 1-e.aiU IRM1-E.90 4l»l.B8iies 1 ,, • .••■ V _ _ n* m ** ff «* *q M M«l A „:..,., 1 Capturing and analyzing long data streams? see»u CHI 590. u CHl> hi M.B9 ': ► / — r Measuring timing relationship between signals? SSnt 533. I* 'Itt- ft I06n. 2. 52 U UC*T ■ ■ CHI 2(1 1ft JOp« 2,54 U UERlH ■ CHI 50B.U e !■«>« ■ 6.803(1Hi H' F1 Z . UO U iMnl iJB.COrn ' UK ■ H,hl . „ , KEFl W10TH • 336m CHI UtttTjl I 0* FUHCTH* UQLTS TIME VtT SLQfr niri ^ ' CUK5DK FUlttUOH rforming complex measurements automaticaUy? Expanding glitches for close analysis? gnal. Or Save on Delta to automatically verify that all parts f your signal fall within prescribed limits. Best of all, ek's line of 100 MS/s digitizing scopes start at just $3995. To find out which Tek scope is right for you, contact our Tek representative, return the card or call Tek irect. We can answer your questions and show you a xrpe that doesn't just look good on paper. It makes your Highest troubleshooting challenges routine. 1-800426-2200* Windowing in on signal details? One company measures up. Tektronix cajwrrrcz] ruL«iuXNCS CIRCLE 92 ON FREE INFORMATION CARD ASK RE Write to Ask R-E, Radio-Electronics, 500-B Bi-County Blvd., Farmingdale, NY 11735 o o cr i- o HI o G < PRINT-SCREEN INDICATOR I'd like to modify my IBM- style keyboard so it has an in- dicator to show when I'm using the print-screen func- tion. Ideally it should be some- thing similar to the caps lock, num lock, and scroll lock LED's that I currently have. Any ideas? — T. Waller, Yorktown Heights, NY What you're asking is one of those things that seem simple but is actu- ally quite complex. It's a kind of "Why is the sky blue?" type question. The first thing to understand is that the PC's keyboard is different from the ones used by Apples and a few of the other popular home computers. The first difference is that it's not a simple matrix keyboard in which each keypress connects two or more wires together to generate a series of highs and lows on a multi-pin connector. The PC keyboard is a serial device, and the standard five-pin connector carries the data, power, clock, ground, and reset signals on sepa- rate lines. The second difference becomes evident once you know of the first difference, since you can't generate serial data without a bunch of silicon. As a result, the PC keyboard is really a small computer in itself and, al- though different keyboard manufac- turers use different IC's, most of them base the keyboard circuitry around a microprocessor specifically designed to handle and control I/O. The 803X, 804X, and 805X micro- processor series from Intel is a fairly common choice. Figure 1 shows the inside of such a keyboard. Knowing those facts, you can see that what you want to do has to in- volve a lot more than piggybacking an LED onto a couple of switches. That isn't to say that what you want to do is impossible. It's an involved project and would more than likely require you to design some circuitry of your own. Keep in mind that, if you build something that sits inside your keyboard and monitors anything other than the output, you'll more than likely be able to use the device only on your own particular keyboard. Different keyboards use different cir- cuitry. There's not enough room here to go into the details of building a circuit like this but I can block out the approach that I would follow. There are two basic approaches to the problem. The first is to monitor the data going from the keyboard to the computer and the other is to cap- ture the particular combination of switch closures in the keyboard be- fore they reach the keyboard's con- troller. I'm not going to take a guess as to which would be easier but, if I was doing this, I'd choose the first alternative since I wouldn't want to take any chance of damaging the key- board circuitry. If you do want to modify the key- board itself, you could try to identify the combination of highs and lows sent on the keyboard's internal data bus whenever you do a Print Screen. Once you've found those, you could FIG. 1 — A PC KEYBOARD is a small computer in itself. This keyboard's circuitry is based on an 8048 microcontroller that's specifically designed to handle and control I/O. buffer and decode them to drive an indicator such as an LED. CABLE TRACER I'd like to trace the path of an underground power cable. One end is above ground and the other end is lost some- where below ground. Neither end is connected to power. Isn't there some sort of wave generator I could build that would provide a signal I could trace with a receiver and an- tenna? — D. Andrew, British Columbia, CA It's really terrific when a simple question like this has a really simple answer. I've faced this problem my- self and I'll pass along the method I used. Most of the commercial equipment that's designed for this purpose works exactly as you described. A signal is sent along the wire and a specially tuned receiver picks it up. Depending on the amount of bells and whistles, that sort of gear can set you back an impressive number of bucks. But there's an alternative. As long as you're sure that both ends of the cable aren't connected to anything, connect the above-ground end to the 120VAC line (through a fuse and ground-fault protector). Once you've done that, connect the noisiest appliance you have to the line and turn it on. The best ones to use are those with motors that have a set of old brushes in them. You can usu- ally spot that by seeing whether lots of sparks are created where the brushes ride on the motor. Each one of the sparks is generat- ing a lot of RF noise that's being transmitted down the cable. You can detect the noise with a portable radio since the noise spreads across a wide band of the spectrum. All you have to do is tune the radio between stations (you may find the AM band is better), turn up the volume, and fol- low the static across the ground. This may seem a primitive method but it's exactly the method used by the "high priced spread." 12 KEYBOARD UPGRADE How can I make a 101 -key keyboard from an IBM AT op- erate with an IBM-compatible WYSE PC+ model WY-1400- 20? I would be willing to build some simple circuitry if it's necessary.— B. Van de Ayr, Chehalis, WA While there's probably no reason why you can't do what you want, there are a few problems in getting it done. I'm not familiar with either the Wyse-PC+ or its keyboard but, just because the computers are compati- ble, there's no guarantee that the key- boards are compatible. (There are different degrees of compatibility.) Not all models of IBM keyboards are interchangeable with each other. The keyboards designed for the XT, for example, will not work with the AT. If you're dead set on modifying or adapting the Wyse keyboard for use with your AT-compatible computer, you'll need some very specific infor- mation before you can get started. • You need a list of the scan codes produced by the Wyse keyboard and those required by the AT-compatible. • You need a schematic of the Wyse keyboard that shows, among other things, the pinouts of the output con- nector and how the data is transmit- ted to the computer. • Although not strictly necessary, make sure the scan codes for the extended function keys(F11 and F12) are compatible with the IBM. • Be certain that both the power and reset requirements of the Wyse key- board can be supplied by the IBM. There's one other thing to be aware of since you're trying to use the key- board with an AT, rather than an XT. In AT-class computers, the data from the keyboard is handled by a pre- programmed microcontroller in the computer itself. There are a few com- panies (Phoenix, AMI, etc J that can supply that, but they are not all com- patible with each other. That is usually a consideration only for setting the CMOS configuration memory of the computer, but keep in mind. Adapting the Wyse keyboard may turn out to be something as trivial as changing the connector on the end of the cable but. considering the fact that you can buy a keyboard for about fifty bucks, you have to wonder it's really worth the effort. R-E Try the MZBEntnmics bulletin board system (RE-BBS) 516-293-2283 The more you use it the more useful it becomes. We support 300 and 1200 baud operation. Parameters: 8N1 (8 data bits, no parity, 1 stop bit) or 7E1 (7 data bits, even parity, 1 stop bit). Add yourself to our user files to increase your access. Communicate with other R-E readers. Leave your comments on R-E with the SYS0P. RE-BBS 516-293-2283 Be an FCC LICENSED ELECTRONIC TECHNICIAN! Earn up to $30 an hour and more! JiJ .rn at home in spare time, previous experience needed! No costly school. No commuting to class. The Original Home-Study course prepares you for the "FCC Commercial Radio- telephone License" This valuable license is your professional "ticket" to thousands of exciting jobs in Communications. Radio- TV, Microwave, Maritime, Radar, Avionics and more... even start your own business! You don't need a college degree to qualify, but you do need an FCC License. No Need to Quit Your Job or Go To School This proven course is easy, fast and low costl GUARANTEED PASS— You get your FCC License or money refunded. Send for FREE facts now. MAIL COUPON TODAY! " commdND "productions" " FCC LICENSE TF1AINING, Dept. 90 P.O. Box 2824, San Francisco, CA 34126 Please rush FREE details immediately! ADDRESS . CITY Made in the U.S. A. Building the best DMM for [lie money is no accident The new RMS225 was carefully desigied to give you what you wanted at a price you could afford. Visit your local distributor today and you'll agree die choice is obvious. Fluke Model 77 Beckman Industrial RMS22S 3->A Digits 4 Digits 3,200 Counts 10,000 Counts 0.3% Accuracy 0.25% Accuracy Touch Hold 9 Prone Hold™ 31 Segment Analog Bar Graph 41 Segment Analog Bar Graph 2,000 Hour Battery Life 1,000 Hour Battery Lite 10A Range fam 10A Range (fumi Protective Holster Protective Holster 3 Yr. Warranty 3 Yr. Warranty True RMS Auto Mln Max™ Relative Mode $159' SW9 ' s Touch Hold is a registered trademark of the John Fluke Mfg. Co., Inc. "1990 Hoke and Philips Catalog Beckman Industrial" An AiUhate of Emerson Electric Co Instnimenutlton Producis Division 3883 Ruffin Road, San Diego, CA 92123-1890 (619) 495-5200 - FAX (619) 268-0172 ■ TLX 249031 Outside California 1-800-854*2708 vViihin California 1-800-227-9781 © 1990 Bcdanin Industrial 1 Corporation Specif jcukais subject to diangc without notice. Flute is a ngjirwl tnotm&A of John Flute Mfe Cci. lnc JHl^O-G 1-Q59I CIRCLE 98 ON FREE INFORMATION CARD £ $ 13 mm Call (800) 992-9943 Over 35,000 Electronic Components Call Today for Your FREE SUBSCRIPTION If You Order Today, WE SHIP TODAY!! Stocking Locations Across America. CIRCLE 117 ON FREE INFORMATION CARD LETTER5 Write to Letters, Radio-Electronics, 500-B Bi-County Blvd., Farmingdale, NY 11735 MAC PLUS FIX I would like to thank Radio-Elec- tronics for the fine article on build- ing a Mac clone (January 1991), My Mac Plus nuked itself last week. I removed the power board and. upon taking the board to two Apple deal- ers , I was told that it would cost $300 to fix — and I would have to put the board back in the Mac and then bring them the whole machine. No way! I opened the magazine and called Pre- Owned Electronics. They sent me the board in two days for $119. I want to thank you guys forall the help in locat- ing decent merchants who want to do honest business. Keep up the good work. RICHARD RUSSO TABLE THAT TABLE! I read the article "1 Volt = ?" (Ra- dio-Electronics, February 1991) with considerable interest. It was well I en g z o cr i- o LU O □ < IX 14 A 1 Makey. servicing K ft/*^ *^ * problems disappear u fli%4 ■ fn "' l lo trace with the latest ^^\rV^C^. M f^Ak^ from the eomp 17 lliL*^\l video servicing ben kila. \ ^S Fifth in a series of service bulletin » compilations, the SB-09 features ninety-five pages of valuable troubleshooting information for populi and Qua*. ncr cameras, camcorders and video cass' ders manufactured between 1983 and 1990. To order you r SB -0.' '■' ') eck or money order for # i lering from NJ ) to the address below. 7 amounts include shipping and handling charges, and l applu -.n elude a copy of this ad with your order. A How 4 -8 weeks for ■ CD's, charg Reo serv lids by M Matsushita Services Company fochnlcal A d /?■ Doc. ita! IdcltC^U^iJ} Bd^L imm written and comprehensive. It con- tained a gratifying amount of basic physics and pulled together a great many ideas that are often hard to find because they are scattered over sev- eral different chapters in various text- books. Were it not for one fundamental flaw. Table 1 would be an extremely useful reference for students of sev- eral academic disciplines. The author used an obsolete and (now) non- standard set of base Cor principal) quantities. Intellectually and philosophically I like the author's choice of charge as a base unit and his derivation of dimen- sional equivalents in terms of cou- lombs. I also still "like" to use mhos, micro-microfarads, milli-microamps, and kilo-megacycles. Nevertheless, those outdated standards are all con- trary to the American National Stan- dards that have been in effect for some time now and really are the ones that should be used. If the author and your editors would check the IEEE Dictionary for "units and letter symbols," I believe they will find that the electric base quantity (in the SI system) is current, not charge. Charge is now properly described as a "derived" quantity that has dimen- sions of (current x time) or ampere- seconds. Regrettable, that means that in each of the author's "Dimen- sional Equivalents" in Table 1, the Coulomb (C) term should be re- placed with (A x s), and the terms re- collected. I know this all seems perverse to old-timers who learned to start with the charge on the electron and to calculate how many electrons it takes to make a coulomb, but there is a good practical reason for the change. When you use current as the base unit for electrical measurement, you can define the ampere in terms of the force exerted upon two parallel con- ductors. That is evidently something that is more directly measurable in terms of mass, length, and time — and more up-to-date. LUCIUS DAY Lakewood, CO CIRCLE 190 ON FREE INFORMATION CARD REMOVING IC'S Thank you for the years of excel- lent reading in the extremely diverse field of electronics. I've been reading Radio-Electronics on and off for some years, and have enjoyed every issue. Now for the good news. Over the years I have read letters from readers about the handling of IC's and the questions concerning their abuse. Well, here is some shocking news. When chips CTLL's, CMOS, etc.) are manufactured, they are dipped in a molten material. Notice I said molten, which means that the material is in liquid state. The material used and the temperature of that material must give off heat during the change of state from liquid to solid. Thinking about that concept, I began to work on a way to extract circuit-board com- ponents without the use of desolder- ing tools, and one that would save plenty of time. Try this out for size: Using a hot oil bath as a desoldering fluid and keep- ing the temperature down to a level that the IC's could handle, I dropped the board in, and within seconds parts began to fall off the board. The temperature of the oil bath should be no lower than 370°F and no hotter than 380°F. That temperature is with- in an IC's tolerance. The only exception is electrolytic capacitors, as they will explode and send hot oil all over the place. Use gloves and eye protection dur- ing this process. I have extracted hun- dreds of useful parts that way and have had an 80% success rate. I said 80% because some plastics cannot withstand that temperature, and the hot oil can break down some plastics altogether. 1 hope your readers can use this information— but if you do, be sure to observe safety first. And thanks again for the excellent reading materi- al. Keep up the good work. MICHAEL BROWN Stockton, CA Your method sounds a tittle dan- gerous to us, but it does show that where there 's a will, there s a way! — Editor AM PROBLEMS Since Radio-Electronics printed the article "Whatever Hap- pened to AM Radio" (September 1990), I thought the editors and read- ers might be interested in the reply I received from my congressman in re- ply to my suggestion that AM stereo circuitry be mandatory in future AM/ FM stereo equipment. Congressman Dale E. Kildee said, in part, "In recent years, new technologies have been employed that have led to a wider use of AM stereo components. At this time, no legislation has been intro- duced in the House of Represen- tatives that would require stereo manufacturers to place AM stereo components in their equipment." All three AM-only radio stations in my area were sold at bargain prices last year — one at auction, one in bankruptcy court, and one to a church. Only the latter, a gospel sta- tion, emerged with no major changes. The first, which was a lead- ing Top-40 station in the 60's and 70s, became a Christian station whose last Arbitron rating was 0.0. The second, formerly the leading news and information station, switch- ed to a satellite-fed, heavy- metal rock format called "Z-Rock." Despite adding AM stereo equipment, the station was not successful, and went off the air. The owner (who also owns a mobile-home sales lot and added another one on the radio-station grounds) plans to try another format, but as of this writing the station is still off the air. It would appear that your article is right on the mark concerning AM ra- dio's problems. GARY FLINN Flint, Ml WRIST STRAPS Steve Swenton's statement on using a wrist strap when desoldering static-sensitive devices (Letters, Ra- dio-Electronics, September 1990), "...always use a ground strap (a metal wrist strap with a detachable ground wire) and connect its wire to ground,..," needs further clarifica- tion, lest someone fashion a home- made wrist grounding strap from that description. Commercially available wrist strap/ground wires contain a current- limiting resistor, usually 1 megohm, in order to protect the operator. One should never connect oneself to a hard ground when working around sources of potentially lethal (e.g., household) current, JOHN L. HORNBY Madison, CT Earn Your B.S. Degree in ELECTRONICS or COMPUTERS By Studying at Home Grantham College of Engineering, now in our 41st year, is highly ex- perienced in "distance education" — teaching by correspondence— through printed materials, computer materials, fax, and phone. No commuting to class. Study at your own pace, while continuing on your present job. Learn from easy-to- understand but complete and thorough lesson materials, with additional help from our instructors. Our Computer B.S. Degree Pro- gram includes courses in the BASIC, PASCAL, and C languages — as well Assembly Language, MS DOS, CADD, and more. Our Electronics B.S. Degree Pro- gram includes courses in Solid-State Circuit Analysis and Design, Control Systems, Robotics, Analog/ Digital Com- munications, and more. An important part of being pre- pared to move up is holding the right college degree, and the absolutely neces- sary part is knowing your field. Grantham can help you both ways — to learn more and to earn your degree in the process. Write or phone for our free catalog. Toll free, 1-800-955-2527, or see mailing address below. Accredited by the Accrediting Commission of the National Home Study Council GRANTHAM College of Engineering Grantham College Road Slidell, LA 70460 I 15 XT-TO-AT UPGRADE Having worked for a company that manufactures floppy disks, I'd like to make several comments concerning the differences between various disk formats. It's true that 5'/i-inch, high-density CI .2 MB) drives have twice as many tracks as the regular 360K drives. That doesn't increase the chance of crosstalk, however, because the track width (the width of the track written or read by the head) is, of course, also half as great. tt isn't a case of the write current being decreased on high-density (HD) drives. Instead, the write field is increased. That is necessary be- cause there is a fundamental dif- ference between disks designed for HD operation and non-HD operation: The HD disks' coating material needs a ri/g/ierfield to reliably saturate (i.e., be fully magnetized one way or the other). The software on an AT can change the write current on an HD drive. There's a pin specifically for that on the drive interface, and the BIOS can flip it when required. Indeed, it has to reduce the write current when writing to 360K disks because otherwise the excessive write field would cause each transition, as it was being writ- ten, to affect the previously written transition. The recorded level may seem low when reading on a 360K drive a disk written on a 1.2-MB drive, but that is because only one-half the normal track width has been written, causing a reduced signal output of approxi- mately 70%. I have never had any problems from that, since drives are rated to work with dropouts to 45% remaining signal and below. However, it is true that the loss of signal level does reduce your operating margin against problems like misalignment and drift. Of course, HD drives are rated to work with 360K-formatted disks despite the reduction in avail- able signal level. Where problems most often arise is when disks are overwritten by a succession of different drives. Re- member that HD drives can write only half-width tracks (relative to a 360K drive). So if a track is written "wide" and overwritten "narrow," a "wide- reading" drive will read both the new, wanted, narrow track and the rem- nant of the old wide track together. Remember that the directory area of the disk is rewritten whenever you add a file! The above problem may render every one of the files on the disk inaccessible from the addition of a single file, because the entire direc- tory has been corrupted. For the sake of completeness, I should mention that, while 3'/s-inch HD disks have a different material from regular (720K) 3'/2-inch disks, there is no difference in track widths, ruling out the problem of overwriting. Also, the coating materials are similar enough that a 720K diskette can often be formatted for 1 .44 MB with- out any errors reported during the format. However, the non-HD disks are highly marginal with the HD for- mat, and you are highly likely to en- counter reliability problems. Recent 1.44-MB systems have implemented a sensor that detects the HD hole to prevent non-HD disks form being in- correctly formatted. It is probably also undesirable to format 3'/2-inch HD disks as 720K. but I haven't checked into that. DANNY WILLIS Munich, Germany o z o d I- o UJ _i LLJ o < DC EARN YOUR Dibit it , DEGREE THROUGH HOME STUDY Our New and Highly Effective Advanced- PEace- roent Program for experienced Electronic Tech- nicians grants credit for previous Schooling and Professional Experience, and can greatly re- duce the time required to complete Program and reach graduation. No residence schooling re- quired for qualified Electronic Technicians. Through this Special Program you can pull all ol the loose ends of your electronics background together and earn your B SEE. Degree. Up- grade your status and pay to the Engineering Level. Advance Rapidly! Many Ifnish in 12 months or less. Students and graduates in aJ 50 States and throughout the World. Established Over 40 Years! Write for fre* Descriptive Lit- erature. COOK'S INSTITUTE OF ELECTRONICS ENGINEERING 4*£(VE: 435! CYPRESS DRIVE *s£'-*.E JACKSON, MISSISSIPPI 39212 16 CIRCLE 58 ON FREE INFORMATION CARD JAN CRYSTALS your reliable source for a world of crystal clear communication • Commercial Two-Way • Microprocessors • Amateur/Experimental • Scanners/Monitors/Pagers • Satellite-Telemetry • Plus custom applications EXPEDITED ORDER SERVICE! FOR FREE CATALOG, CALL OR WRITE: JAN CRYSTALS P.O. Box 06017 Ft, Myers, FL 33906 (813) 936-2397 TOLL FREE 1-800-526-9825 FAX ORDERS: 1-813-936-3750 VISA CIRCLE 104 ON FREE INFORMATION CARD CIRCLE 108 ON FREE INFORMATION CARD HOW MUCH SHOULD YOU PAY FOR 10 INSTRUMENTS, 39 FUNCTIONS AND 4000 COUNT ACCURACY? Just $139.95 if you say PROTOMETER ! [Tj DC VOLTMETER [2] AC VOLTMETER [Tj OHMMETER [Tj 20A AMPMETER [Tj DIODE/LED TESTER \±\ TRANSISTOR TESTER \T\ CAPACITANCE TESTER [Tj FREQUENCY COUNTER {9} LOGIC PROBE [10) CONTINUITY TESTER PROTOMETER™ 4000 is the Professional Multi-Function Por- table Instrument System. Ten test instruments in a 3-3/4 Digit, 4000 count handheld package. Pack- ing the power of our complete instrument line. Combining a digi- tal multimeter, frequency counter, transistor/capacitance tester, and more into a durable no-nonsense =SSV Cal1 Toil-Free For Details 1-800-572-1028 drop-resistant case. Plus standard features like a large LCD display, peak hold, and a unique high-volt- age warning indicator. Looks like the competition's DMM and priced like one too! GLOBAL SPECIALTIES CIRCLE 192 ON FREE INFORMATION CARD But PROTOMETER™ 4000 is much more than a DMM. Com- pare for yourself. Clearly the best value in portable instruments. Why pay just as much for a DMM, when you can get ten test instruments for one low price. How much should you pay? Just $1 39.95, if you say PROTO METER™ 4000. Order Yours Today!! $1 39.95 Global Specialties' A028 70 Fulton Terrace. New Haven. CT 06512 Telephone :(203) 624-3 103, ©Interpleji Electronics, 1991 S CO to 17 No other training— anywhere— shows you service computers Now includes AT-compatible, 20 meg hard drive, and exciting new diagnostic package! Only NRI walks you through the step-by-step assembly of a powerful AT-compatible computer system you keep — giving you the hands-on experience you need to work with, troubleshoot, and service all of today's most widely used computer systems. With NRI at-home training, you get everything you need to start a money-making career, even a computer service business of your own. No doubt about it. The best way to learn to service computers is to actually build a state-of-the-art computer from the keyboard on up. And that's just what you do when you train with NRI. As you perform key tests and demonstrations at each stage of assembly, you see for yourself how each part of your computer works, what can go wrong, and how you can fix it. Only NRI, the leader in career- building electronics training for more than 75 years, gives you such practical, real-world computer servicing experience. Indeed, no other training — in school, on the job, anywhere — shows you how to troubleshoot and service computers like NRI. You get in-demand computer skills as you train with a powerful AT-compatible computer system — now with 1 meg RAM and 20 meg hard drive With NRI's exclusive hands-on training, you actually build and keep the powerful new AT-compat- ible West Coast 1010ES computer, complete with 1 meg RAM and 20 meg hard disk drive. You start by assembling and testing the "intelligent" keyboard, move on to test the circuitry on the main logic board, install the power supply and 5-^" highnJensity floppy drive, then interface your high- resolution monitor. But that's not all. Your NRI hands-on training continues as you install a powerful 20 megabyte hard disk drive — today's most- wanted computer peripheral — included in your course to dra- matically increase your computer's data storage capacity while giving you lightning-quick data access. DIGITAL MULTIMETER Professional test instrument for quiet and easy circuit measurements. +A gg* HARD DISK DRIVE Tne 20 megabyte hard disk drive you install internally gives you greater data storage capacity and access speed. AT-COMPATIBLE COMPUTER 80286 CPU (12 MHZ dock, wait sales), I meg RAM (expandable to 4 meg), 1.2 meg hiijHlin-.il', floppy disk drive. LESSONS Gearcut, illustrated texts build your understanding of computers siep by sup. SOFTWARE kam to use MS-DOS, GW-BASIC, and the popular new Microsoft' Works integrated software package. New! Training now includes Ultra-X diagnostic hardware and software for quick, accurate troubleshooting! Now NRI takes your hands-on computer servicing experience an important step further: Now you train with and keep the remarkable R.A.C.E.R. plug-in diagnostic card and QuickTech diagnostic software from Ultra-X — professional diagnos- tic tools that make computer troubleshooting fast and accurate. Using these state-of-the-art tools, you learn to quickly identify and service virtually any computer in school, on the job, how to troubleshoot and likeNRI MONITOR High-rcsoluTion, rtrnglarti 12' TTL monochrome monitor wilh till and swivel base. TECHNICAL You get "inside* your AT-compatiblc computer system with exclusive NRI Training Kit Manuals plus technical specs direct from the mamifoaurer. DISCOVERT LAB Complete breadboaniing system to let you design inJ modify circuits, diagnose and repair faults. DIGITAL LOGIC PROBE Using your logic probe. you get firsthand experience inatyting digital circuit operation. problem on XT, AT 80286/80386, and compatible machines. You discover how to use the R.A.C.E.R. card to identity individual defective RAM chips, locate interfacing problems, and pinpoint defective support chips. Plus you learn to use your QuickTech diagnostic soft- ware to test the system RAM and such peripheral adapters as parallel printer ports, serial communica- tions ports, video display memory, and floppy and hard disk drives. Only NRI gives you such confi- dence-building, real-world experi- ence. Only NRI gives you both the knowledge and the professional tools to succeed as today's in- demand computer service technician. No experience needed... NRI builds it in You need no previous experience in comput- ers or electronics to succeed with NRI. You start with the basics, following easy- to-read instructions and diagrams, moving step by step from the fundamentals of electronics to sophisti- cated computer servicing techniques. With NRI's unique Discovery Learning Method, you're sure to get the kind of practical, hands-on experience that will make you fully pre- pared to take advan- tage of every opportu- nity in today's top- growth computer service field. You learn at your own conve- nience, in your own home. No classroom pressures, no night school, no need to quit your present job until you're ready to make your move. And all throughout your training you've got the full support of your personal NRI instructor and the entire NRI technical staff, always ready to answer your questions and help you achieve your training goals. Your FREE NRI catalog tells more Send today for your free, full-color catalog describing every aspect of NRI's innovative computer training, as well as hands-on training in video/ audio servicing, telecommunications, industrial electronics, and other growing, high-tech career fields. If the coupon is missing, write to NRI School of Electronics, McGraw-Hill Continuing Education Center, 4401 Connecticut Avenue, NW, Washington, DC 20008. AT is a registered trademark of International Business Machines Corporation. R.A.C.E.R. and QuickTech are registered trademarks of Ultra-X, Inc. SEND TODAY FOR FREE CATALOG r Schools mt McGraw-Hill Continuing Education Center *i'fl 4401 Connecticut Avenue, NW T Washington, DC 20008 l.fl I ^ CHECK ONE FREE CATALOG ONLY For career courses ] approved under Gl Bill, check for details. □ D Microcomputer Servicing D □ TV/Video/Audio Servicing □ □ Telecommunications O D Industrial Electronics &. Robotics Q □ Security Electronics n □ Electronic Music Technology □ D Basic Electronics d Computer Programming PC Systems Analysis PC Software Engineering Using C Desktop Publishing & Design Word Processing Home Business Paralegal Ftction/Nonfiction Writing Automotive Servicing □ Building Construction D Air Conditioning, Heating, & Refrigeration D Electrician D Small Engine Repair G Locksmithing □ Bookkeeping & Accounting Nunc (please print) Age Address City/State/Zip Accredited Member, National Hume Study Council 1-051 CATV-RF SIGNAL ANA- LYZER. The FS74A Chan- nelizer Sr, from Sencore includes an exclusive, all- channel, microprocessor- controlled tuner for testing all standard and cable channels to FCC accuracy, including the return chan- nels, sub-band, off-air VHF, UHF, and FM. By selecting FCC. HRC. or ICC carrier shift tuning, the user can simply dial in the channel and read the video or audio signal level displayed in mi- crovolts or dBmV on the fully-autoranging meter. The FS74A also allows the user to analyze the audio/ video ratio on any channel without calculations, by setting the function control to the A/V position and reading the ratio in dB. Sencore's patented on- channel automatic signal- to-noise ratio test elimi- nates time-consuming sig- nal comparisons and cal- culations that are usually required when referencing noise on an unused chan- CIRCLE16 0N FREE INFORMATION CARD nel. Another patented fea- ture, the automatic dB- h urn- level test, measures hum on any modulated channel, and measures AC and DC volts through the RF input jack. The built-in digital voltmeter also can be used to measure AC and DC voltage, as well as ohms. The unit's built-in wideband (4-MHz) video monitor shows picture- quality and sync-compres- sion problems. For porta- ble use, the signal analyzer can be powered by two field-rechargeable bat- teries. A carrying case, strand hook, and IEEE 488 and RS-232 interfaces are available as options. The FS74A Channelizer Sr. TV-RF signal analyzer costs $3495. — Sencore, Inc., 3200 Sencore Drive, Sioux Falls, SD 57107; Phone: 1-800-SENCORE. LOGIC ANALYZER. De- signed for applications in circuit design, digital test- ing, ATE development, edu- cation, microprocessor de- sign and debugging, and logic analysts. Rapid Sys- tems' R3800 logic analyzer features 16K data buffers for each of 32 input chan- nels, allowing users to cap- ture long, high-speed dig- cg ital signals at a 100-MHz 2 sample rate. Powerful PC- g based software simplifies £ setup and measuring, and 4j provides selectable sample £ rates to 100 MHz. The 5 R3800 also offers complex ir triggering with a sequence of four 32-bit data patterns, trigger delay of up to 64K clocks, four trigger levels with data qualifiers, and a zoom-display function. It can load, save, and print CIRCLE 17 ON FREE INFORMATION CARD displays and files and can list in Hex, Bin, ASCII, or Dec. The R3800 32-channel logic analyzer costs $3995 —Rapid Sys- tems, Inc., 433 North 34th Street, Seattle, WA 98103; Phone: 206-547-8311; Fax: 206-548-0322. PORTABLE VIDEO FRAME GRABBER. With a low-power design that al- lows it to operate for up to ten years on a single 9-volt lithium battery, Portable Technologies' PFG-1 pro- vides a portable, conve- nient, and affordable way to do gray-scale image cap- ture from live video sources. The unit is contin- uously powered and ready for frame-grabbing at any time. The resultant image has a resolution of 320x320 pixels with 64 levels of gray. Square pixels are obtained with standard NTSC or RS-1 70 video sig- nals from video cameras, camcorders. VCR's, or TV monitors. The PFG-1 can digitize and store a video frame in- dependently in Veo of a sec- ond. The captured image is stored in internal memory until overwritten by another frame grab. The stored im- age can be transferred to any computer equipped with a standard RS-232 in- terface. There are no add- on cards to install. Frame CIRCLE 18 ON FREE INFORMATION CARD grabbing can also be initi- ated under computer con- trol via the serial interface. The frame grabber comes with PGRAB soft- ware, which runs on IBM- PC and compatible com- puters with CGA, EGA, or VGA and at least 128K of RAM. The software allows 22 Elelctninics, DTfDDDTlD THE MODEL WTT-20 IS ONLY THE SIZE OF A DIME, yet transmits both sides of a tele- phone conversation to any FM radio with crystal clarity. Telephone line powered - never needs a battery! Up to '/< mile range. Adjusta- ble from 70-130 MHZ. Complete kit $29,95 + $1.50 S + H. Free Shipping on 2 or more! COD add $4. Call or send VISA, MC, MO. DECO INDUSTRIES, Box 607, Bedford Hills, NY 10507. (914) 232-3878. CIRCLE 127 ON FREE INFORMATION CARD COMPUTER KITS, BOARDS & COMPO- NENT PARTS. Designed to the highest de- gree of quality and reliability available today. They're fun, easy to build, educational, IBM compatible, very powerful, and at great prices. All items are pre-tested, include a full year warranty, step by step assembly manual, and free tech support. Assembly available at no extra charge. For free catalog contact: GENERAL TECHNICS, P.O. BOX 2676, LAKE RONKONKOMA, NY 11779, or call (516) 981-9473. VISA, MasterCharge, Ameri- can Express, COD. CIRCLE 176 ON FREE INFORMATION CARD FREE CATALOG! ELECTRONIC TOOLS & TEST EQUIPMENT. Jensens new Master Catalog, available free, presents major brand name electronics toois, tool kits, and test in- struments, plus unique, hard-to-find products for assembly and repair and custom field ser- vice kits available only from Jensen. All fully described and illustrated. Enjoy free technical support and rapid, post-paid delivery any- where in the Continental USA, JENSEN TOOLS INC., 7815 S. 46th St., Phoenix, AZ 85044. Phone: 602-968-6231; FAX: 1-800-366-9662. CIRCLE 115 ON FREE INFORMATION CARD ZF1 ZF2 CABLE TV CONVERTERS AND DE- SCRAMBLERS SB-3 $79.00 TRI-BI $95.00 MLD-$79.00 M35B S69.00 DRZ-DIC $149.00. Special combos available. We ship COD. Quantity discounts. Call for pricing on other products. Dealers wanted, FREE CATA- LOG. We stand behind our products where others fail. One year warranty. ACE PROD- UCTS. P.O. Box 582, Saco, ME 04072 1 (800) 234-0726. CIRCLE 75 ON FREE INFORMATION CARD ZENITH TEST CHIP (ZF1). New improved Data Injector Fully activates Z-tacs $29.95 No jumpers to cut. Just solder 4 wires and plug chip into socket. ZENITH TEST BOARD (ZF2) Fully activates the 165 chip on the 288 chip's data stream. $49.95 Both units for test purposes only, not for signal theft. PHONE: 800-722-9381 CALL NOW AND RESERVE YOUR SPACE • 6 x rate $940.00 per each insertion. • Fast reader service cycle. • Short lead time for the placement of ads. • We typeset and layout the ad at no additional charge. Call 516-293-3000 to reserve space. Ask for Arline Fishman. Limited number of pages available. Mail materials to: mini-ADS, RADIO-ELECTRONICS, 500- B Bi-County Blvd., Farmingdale, NY 11735. FAX: 516-293-3315 APPLIANCE REPAIR HANDBOOKS— 13 volumes by service experts; easy-to- understand diagrams, illustrations. For major appliances (air conditioners, refrigerators, washers, dryers, microwaves, etc.), elec. housewares, personal-care appliances. Basics of solid state, setting up shop, test instruments. $2.65 to $7.90 each. Free brochure, APPLIANCE SERVICE, P.O. Box 789, Lombard, IL 60148. (312) 932-9550. CIRCLE 84 ON FREE INFORMATION CARD SIMPLY SNAP THE WAT-50 MINIATURE FM TRANSMITTER on top of a 9v battery and hear every sound in an entire house up to 1 mile away! Adjustable from 70-130 MHZ. Use with any FM radio. Complete kit $29.95 + $1,50 S + H. Free shipping on 2 or more! COD add $4. Call or send VISA, MC, MO. DECO INDUSTRIES, Box 607, Bedford Hills, NY 10507. (914) 232-3878. CIRCLE 127 ON FREE INFORMATION CARD to 23 •rSave on cable rental fees !» CABLE TV DESCRAMBLERS WE'LL BEAT ANY PRICE! CALL TOLL- FREE 1-800 284-8432 JERROLD-TOCOM-ZENITH HAMLIN-OAK-PIONEER SCIENTIFIC ATLANTIC ■24 HOUR SHIPMENTS t • MONEY BACK GUARANTEE I 'FREE CATALOG 8, INFO t 'QUANTITY DISCOUNTS ! MASTER CARD / AMEX / VISA / C.O.D. Have make and model number of equipment used in your area ready 1-800-284-8432 CABLE WAREHOUSE 4700 N. HIATUS R0AD,SUNRISE,FIA33351 V,, _ NO FLORIDA S^LES >*J CIRCLE 180 ON FREE INFORMATION CARD Try the HectnmtES, bulletin board system (RE-BBS) 516-293-2283 The more you use II the more useful It becomes. We support 300 and 1200 gaud operation. Parameters: SHI (B data alts, no parity, 1 stop bit) or 7E1 (7 data bits, even parity, 1 stop bit). Add yourself to our user flies to increase your access. Communicate with other R-E readers. Leave your comments on R-E with the SYSOR RE-BBS 516-293-2283 A ■ ATTENUATION - 45 dB TYPICAL ■ BANDWIDTH - 4 MHz AT 5 dB POINTS ■ INSERTION LOSS - 2 dB MQQC4 FOR CHANNELS PA39UHD Pfl.CE SH!PPiHO J3K EC-££ MM.. 2 3 for 6 ritit' nam| SO-300UHI MO NO SHIPPING or COD. CHARGES 46 FM 66 10! WHi 4.5 6 (or any FM} 50-300 MHz 130 1*17 120.144 MHz !4[A)15(BH»[CH7(D] 50-400 MHz t?Q 1 822 1 44-1 74 M Hi lr)(El 19(F) Z«|G) 21(H) 22 (l| 50-40C MH: J30 713 174-216 MHz 7.1.9.10.11.12.13 50-400 MH: 530 CO o z o g Q < 3 for $75 - 10 for $200 - mix or match CALLTOiLFREEFORCO.D.ORSENDCHECKTOORDER FAST DELIVERY 30 D A Y MON EY BAG K GU AR ANT EE (3 FILTE R L IM IT) Star Circuits P.O. Box 94917 Las Vegas, NV 39193-491 7 1-800-433-6319 bleshooting and installing electronics in tight places such as computer boards, under a car dashboard, or behind an arcade game. Another convenience fea- ture that comes in handy in awkward spots is the data hold function, which lets the user manually "freeze" the display so that it can be moved from the measure- ment point to take the reading. Other features of the DM73 include an audible continuity check, a buzzer that sounds when chang- ing functions, a built-in scabbard for the ground probe, and a display of the function in use. The DMM has full auto-ranging ca- pability on 12 measurement ranges. DC voltages up to 500V, AC voltages to 250V, and resistance up to 2 megohms are measured using an accurate dual- slope integrating analog- to-digital GVD) conversion technique. The DM73 pen-type dig- ital multimeter, complete with batteries, test leads, and operator's manual, has a list price of $69.95. — Beckman Industrial Corporation, Instrumen- tation Products Division, 3883 Ruffin Road. San Di- ego, CA 92123-1898; Phone: 619-495-3200. PC-CARD PROTOTYP- ING KIT. To provide a broad base of PC-users with low-cost digital-signal- processing (DSP) ca- pabilities, Signal-Systems' is offering DSPerato, a real-time, DSP expansion- card prototyping kit that features a Motorola 56001 DSP chip. Motorola's 56001 DSP runs at 20 MHz, delivers 10 MIPS, and offers advanced tech- nologies including pipeline instruction fetches; parallel data moves to three sepa- rate 24-bit CX-data, Y-data, and program) memories; and easy interfacing to the host computer. DSPerato contains a full-length IBM- PC prototype card that al- ready has a bus decode and buffer printed circuit. The rest of the card has un- committed 0.100 center- plated through holes with power buses and pads. The 56001 DSP and support chips are wired and sol- dered on those pads. Two optional high-perfor- mance video and audio A/D and D/A converter boards can be attached to the card via 0.100 center pin headers. The 16-bit au- dio board uses Motorola's 56ADC 16-bit converter; CIRCLE 23 ON FREE INFORMATION CARD the 8-bit video card uses Sony's 8-bit 20-MHz semi- flash converters. For max- imum flexibility in custom projects, the user can opt for both converters, just one, or neither to be at- tached to the DSP card. Parts needed to popu- late the DSP card and the converter kits — including all chips, sockets, re- sistors, and capacitors as weli as the 56001 DSP and 8Kx 24-bit 45-ns static RAM — are included. The user can add parts as needed to configure the card for custom applica- tions. All assembly instruc- tions and schematics re- quired for connecting the DSP and the converters are also included, along with Signal-Tools software. Signal-Tools' functions in- clude real-time spectrum analysis , digital os- cilloscope, and waveform capture and generation. The software features a keyboard- or mouse-driven pull-down menu interface. 26 Optionally available is a software development kit that contains MACRO- DSP, a 56001 DSP macro assembler for IBM-PC's; a debugger, and linkable ob- ject modules, DSPerato costs $299. the audio and video con- verter boards cost $149 each, and the software de- velopment kit including MACRO-DSP costs S99 Signal-Systems 15105 S.E. East Avenue, Mitwaukie, OR 97267. 800-MHz GROUND- PLANE ANTENNA. Be- cause broad-band scanner antennas perform poorly at higher frequencies, many scanner listeners hear only a small fraction of the sig- nals available on the 800- MHz band. The MAX800 800-MHz ground-plane an- tenna from Cellular Securi- ty Group is a specialized mono-band antenna de- signed to alleviate that CIRCLE 24 ON FREE INFORMATION CARD problem. Based on plans presented in the ARRL Handbook, the element lengths are cut precisely to the proportionate dimen- sions. The design supports the elements, protects the feed-point, and provides a quick and easy mounting. EMThe MAX800 800-MHz ground-plane antenna costs $19.95; optional type-N connector models of long 38-inch PVC mounting masts are avail- able for an additional $ 5 . 00 .—Cellular Security Group. 4 Gerring Road, Gloucester, MA 01930; Phone: 508-281-8892. R-E Try the Hectm miEs r bulletin board system (RE-BBS) 516-293-2283 The more you use it the more useful II becomes. We support 300 and 1200 baud operation. Parameters: 8N1 (8 data bits, no parity, 1 slap bit) or 7E1 (7 data bits, even parity, 1 stop bit). Add yourself to our user til es to Increase your access. Communicate with other R-E readers. Leave your comments on R-E with the SYS0P. RE-BBS 516-293-2283 LEARN VCR CLEANING/MAINTENANCE/REPAIR EARN UP TO S1000 A WEEK.WORKING PART TIME FROM YOUR OWN HOME! THE MONEY MAKING OPPORTUNITY OF THE 1990S IF yen are able to work with common small hand tools , and are (ami I iar wi th bas i c electron i cs ( i . e . able to use voltmeter, understand DC electronics), . . . IF you possess average mechanical ability, and havea VCR on which to practice and learn. . . .then we can teach 1OT VCR maintenance and repair! FACT: u p f o 90% of AL L VCR maltu ratio ns a re d ue to simple MECHANICAL or ELECTRO-MECHANICAL breakdowns' FACT: over 77 million VCRs in use today nationwide! Average VCR needs service or repair every 12 to 18 months! Vlejos 400 PAGE TRAINING- MANUAL (over 500 pho- tos and illustrations) and AWARD-WINNING VIDEO TRAINING TAPE reveals the SECRETS ol VCR mainte- nance and repair— "teal world" information that is NOT available elsewhere! Also includes all the info you'll need regarding the BUSINESS-SIDE of running a successful service op- eration! FREE ikfoRMATION CALL TOLL-FREE 1-800-537-0589 Or write lo: Viejo Publications Inc. 5329 Fountain Ave. Los Angeles, CA 90029 Dept. RE CIRCLE 185 ON FREE INFORMATION CARD FREE CATALOG with over 100 innovations to add comfort and convenience to your home. Latest in electronics. Heath Company's new Home Automation catalog features easy-to- install electronics that bring sophisticated technology into your home for as little as $12.95. Simple. Easy to install. Affordable. Guaranteed. Some bring you peace of mind. Affordable protection for your home or car. Expandable security systems to meet your needs today and tomorrow. Advanced motion sensor lighting that reduces false triggering (often caused by blowing leaves or small pets) by up to 75%, You get protection where and when you need it, indoors and out. Some save you time. Watch the kids play outside, monitor the baby's room, or see who's at the front door just by looking at your television screen. 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Mail to Heath Company, Dept. 020-050, Benton Harbor, MI 49022. II A- 101 I S S 1 27 CIRCLE 86 ON FREE INFORMATION CARD NEW LIT Use The Free Information Card for fast response. w o 2 o □r. h- o LU _J UJ 6 Q < HDTV: HIGH-DEFINI- TION TELEVISION; by Stan Prentiss. Pub- lished by Tab Books Inc., Blue Ridge Summit, PA 17294-0850; Phone: 1-800-233-1128; $16.95. Already a reality in Japan (albeit with a steep price tag and limited program- ming), HDTV is eagerly awaited around the rest of CIRCLE 37 ON FREE INFORMATION CARD the world. More than a doz- en major corporations cur- rently are competing to perfect the revolutionary technology that promises to bring crystal-clear pic- tures and high-quality sound to television. This book is intended to help prepare engineers, techni- cians, students, and mar- keting managers for the unveiling of HDTV. The book provides an in- side look at both the tech- nical and the legislative aspects of high-definition television. It explores the widely divergent industry standards in North Amer- ica, Europe, and Japan that are now impeding HDTV production, and analyzes FCC and congressional regulation of HDTV re- search and development in the U.S. The book explains the competing delivery and receiving systems under development, discussing their pros and cons and de- scribing the methods used to create those systems. In addition, the book covers the progress of HDTV vari- ants that could enhance the performance of stan- dard TV receivers, such as improved-definition televi- sion and extended-defini- tion television. HEATHKIT WINTER 1991 CATALOG. From Heath Company, Department 350-054, Benton Harbor, Ml 49022; Phone: 1-800-44-HEATH; free. Bound into this 60-page catalog is a special "Home Automation" insert that de- votes 28 pages to a variety of innovative products for safety, security, con- venience, entertainment, and energy management in and around the home. Aimed at do-it-yourselfers, CIRCLE 38 ON FREE INFORMATION CARD the home-automation prod- ucts include whole-house automation and security systems, motion-sensing indoor and outdoor lights, wall switches, wireless vid- eo broadcasters, wireless phone extensions, flood sensor alarms, an elec- tronically controlled pet door, and automatic-lawn sprinkling systems. The main catalog includes a va- riety of easy-to-build elec- tronic kits as well as tools, weather instruments, com- puters, amateur-radio equipment, home-enter- tainment products, and home-study electronics courses and videos. CONSUMER ELEC- TRONICS SYSTEMS TECHNICIAN SAFETY GUIDELINES. From EIA/ CEG, Department PS, 2001 Pennsylvania Ave- nue, N.W.. Washington, DC 2006-1813; $1.00. Although manufacturers strive to make their prod- ucts safe to use and to ser- vice, and student techni- cians are taught the inher- ent dangers in the work, technicians often tend to become complacent with experience. This brochure is intended to remind them of possible dangers and to keep safety considerations a conscious part of their work, it contains important safety guidelines that should be followed and up- dated UL requirements for safe installation and servic- CONSUMEH ELECTHONICS SYSTEMS TECHNICIAN SAFETY GITTDEI.TNK5 SAFETY SAFETY SAFETY SAFETY 3 FETt SAFETY SAFETY sflFFTY GUIDELINES GUIDELINES GUIDELINES GUIDELINES GUIDELINES GUIDELINES GUIDELINES ninnFT.TWFP ing of antennas, TV's, and other consumer-elec- tronics products. U.S. GOVERNMENT BOOKS FOR BUSINESS PROFESSIONALS. From U.S. Government Printing Office, Free Business Books Cata- log, Stop SM, Wash- ington, DC 20401 ; free. EXPOB17 IMPORT ._ mum t tudbumu. *ccomrrtNc haxes LAW . Ldur Bdilfeu, Uwi & SUUtiJa Selltajf m ihc Gumiir: — i CIRCLE 39 ON FREE INFORMATION CARD CIRCLE 40 ON FREE INFORMATION CARD Whether you own your own company, have joined the ranks of those who are supplementing their day jobs by running a second business from their homes, or come up with patentable creations on your work- bench, the publications listed in this catalog con- tain information you'll find valuable. Intended to create greater awareness of and access to govern- ment information for the business community, the 22-page catalog contains the most popular govern- ment business books and subscriptions that are sold to the public. Those pub- lications cover such fields as accounting and taxation, selling to the government, exporting, labor law, pat- ents and trademarks, and business statistics, R-E 28 CIE Gives You The Training You Need to Succeed, At Your Own Pace... & In Your Own Home! Discover Your Career Potential In The Fast-Growing Field Of High-Tech Electronics! If you're anxious to get ahead ...and build a real career... you owe it to yourself to find out about the Cleveland Institute of Electronics! CIE can help you discover your career potential in the fast growing field of high-tech electronics. A career that will challenge and excite you every day... re ward you with a powerful feeling of personal accomplishment... and deliver a level of financial security you may have only dreamed of before! As the leading school in home-study electronics, CIE has helped over 150,000 students in the U.S.A. and over 70 foreign countries get started in this exciting field. To find out how CIE could be helping you... read on... then send for a CIE catalog TODAY! A Growing Need For Trained Professionals! The career opportunities shown here are only a few of the challenging, high- paying careers you could enjoy as an electronics technician. 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Each CIE lesson is authored by an independent specialist, backed by CIE instructors who work directly with you to answer your questions and provide technical assis- .„„ tance when you need it. +^ * ^ Practical Training... At Your Own Pace. Through CIE, you can train for your new career while you keep your pres- ent job. Each course allows a gener- ous completion time, and there are no limitations on how fast you can study. Should you already have some electronics experience, CIE offers several courses which start at the intermediate level. "State-Of-The-ArT Facilities & Equipment. In 1969. CIE pioneered the first elec- tronics laboratory course, and in 1 984, the first Microprocessor Laboratory. Today, no other home study school can match CIEs state-of-the-art equipment. And all your laboratory equipment is included in your tuition cost. There is no extra charge— it's yours to use while you study at home and on the job after you complete your course! Earn Your Degree To Become A Professional In Electronics! Every CIE course you take earns you credit towards the completion of your Associate in Applied Science Degree, so you can work towards your degree in stages. And CIE is the only school that awards you for fast study, which can save you thousands of dollars in obtaining the same electronics education found in four-year Bachelor's Degree programs! Send For Your Catalog Today! r jf CIE World Headquarters ■& S € '«*• J5* // /o *E S-f^ 7/f Cleveland Institute of Electronics, Inc. 1776 East 17th St., Cleveland, Ohio 44114 □ YES! Please send me your independent study catalog (For your convenience, CIE will have a representative contact you— (tee is no obligation.) Apt* Area Code/Phone Nq Check to tor G.I. Bill bulletin on educational benefits: o Veteran □ Active Duty Mail This Coupon Today! AE10 to CO 31 PARTS SPECIAL-ORDER HOTLINE. Your local Radio Shack offers a Huge selection of electronic components. Plus, we can special -order over 10,000 items from our warehouse — ICs. tubes, semiconductors, crystals, phono car- tridges and styli, even SAMS* manuals. Delivery time for most items is one week. And there are no postage charges or minimum order requirements. BATTERY SPECIAL-ORDER HOTLINE. In addition to our large in-store stock, Radio Shack can now supply almost any currently manufactured consumer- type battery — quality replacements for cordless telephones, computer mem- ory, camcorders, transceivers, pagers and more. Discover the Radio Shack "hotline" advantage— fast service with no postage or handling charges. I <1) High-Speed 12VDC Motor. Up to 15.200 RPM. About 2" long (with shaft). #273-255 2.99 (2) Ho bby M otor. For robotics a n d projects. 1Va to 3VDC. About 1T plug to XLR jack input. #274-017 . . 11.99 M (S) LCD DVM With Capacitance and Transistor Gain Ranges. Extra-feature digital multitester with easy-to- read 0.5" display and 10 megohm input. 30 ranges- measures AC/DC voltage and cur- rent, resistance, capacitance and transistor gain. #22-194 . . 79.95 (11 Precision Ther- mistor. Resistance changes in proper. lion to temperature. Has measurement range Irom -50 lo + 110° c, #271-110 .... 1.99 (2) Surface-Mount Resistors. Big 200- piece assortment' Popular values, rated 'fc wan, 5%. #271-313. Set 4.9S (3) Ohm's Law Guide. Fast an- swers lo Ohm's law and parallel resist- ance problems. #271-1211 . ...49e (1) Telescoping Antenna. Ex- tends to 24". (16 styles in stock.) #270-1413, 3.99 (2) "N" Battery Holder. (14 other styles in stock.) #270-405 . . 59e (3) Mlnl-Hook Adapters, Slip on test probe tips. #270-334, Pr./2.59 (4) Micro-Hook Test Clips. #270-355 ..2.69 (1) Prewired Tem- perature Module. Just add one "AA" battery for use as a Ihermomeler. You can also connect simple circuits 10 control external indi- cators and devices at temperatures you set. (Data included.) Has 'fe* liquid crys- tal display and selectable Fahren- heit or Centigrade modes Module is easily panel- mounted. #277-123 ...19.95 © 1 '?5.*?c n" !■ Since 1921 Radio Shack has been the place to obtain up-to-date electronic parts as well as quality tools, test equipment and accessories at low prices. Over 7000 locations to serve you— NOBODY COMPARES Prices apply al participating Radio Stuck stores and dealers. Radio Shack is a division oi Tandy Corporation CIRCLE 78 ON FREE INFORMATION CARD Portable Short- wave Antenna. Dramatically im- proves reception on worldband portables! Con- nector clips to tel- escoping rod an- tenna. Antenna wire extends up to 23 feet— and winds up on pocket-size reel for convenient storage, travel. #278-1374, 8.95 (2) Set of 100 Ce- ramic Disc Capaci- tors. A variety of popular styles and values at a bargain price. Ratings up to 1000 WVDC. Stock upl 1272-801, Set 1.98 (3) Assortment of 20 Electrolytic Ca- pacitors. Miniature and s u bm mi types i n a variety ot values wilh ratings 10 50 WVDC. #272.802, Set ot 2fjf 1.96 .Radio /hack AMERICA'S TECHNOLOGY FRED HUFFT EOR EXPERIMENT ,nal-computer h you have probabl of memory cj access memory I or "DRAM" (dy- namic RAM). When troubleshoot- ing a PC memory problem, expanding RAM capacity? or up" grading the cycle speed pi' a mpm ory bank, it can be very helpful lo have a way of function testing and measuring the access tin1e or speed of tfieMiRAM IC's. ManJ intermittent memory failures have been traced to a si' in the memory bank other hand, some DRAMs will far exceed their minimum access rating and can be speed tested and sorted for faster functions, saving the cost difference to the faster rated parts.' A number of small DRAM test- ers are available from ^bout $150 to $1000, with the less-expensive models not having Jk lot . of fea- tures. However, if you are inter- ested in buildjTjg a' multi- featured unit that can function test, accurately speeds 'test, and automatically cycle the 1 tests un- der high-, low-, or normal-voltage margins, all for less than $60" - (plus enclosure and AC adaptor), then check out this easy-to-as — semble DRAM Tester. Capabilities The unit can test 64Kxl. 256KX1, or lMEGxl DRAM's, , and can measure speed or access * times from 60 to 200 nanosee conds (ns). There is a switch, "fo select a "HI" and "LO" voltage- / margin test and three LED in-' dilators that show the current deviee-under-test (DUT) voltage. There's also a red/green LED that blinks green to show a test is run- ning, displays a continuous green to show a test has run com- plete without an error, and will display a continuous red when a test is stopped by the detection of an error. An 18-pin Z1F (zero insertion force) test socket is provided for 'uiid a sophisticated DRAM tester witfy functi on-s peed, and margin test. for under $60! vm ^*° ****r -*v^ 'l-MEG DRAM's l test socket is us_ and 256g DRAM's. A pushbutton test switeh"starts a test se^ quence. which runs about, 10' Lo 14 seconds depending on th"5 ac* cess speed. However, a cycle switch is provided to continu- ously recycle the selected test, if desired. When a 1-MEG DRAM is tested, a 0101 data pattern is written to all addresses in the DRAM, then each address is read back and compared for correct in ZIF data. An error stQp* will occur fnrr- the data is not correct. After the 0101 pattern test, a 1010 pattern is written to all loca- tions, then read back and com- ■ pared. The two-pattern test is automatically run twice: upon successful completion of the two- pattern double test, the tester stops and indicates a continuous green on the pass/fail indicator. A 256K DRAM receives the same test except that it's written to o z o F- O UJ g Q < r£ to and read back 4 times during each test and a 64K DRAM re- ceives the write/read test 16 times in each pattern. If the cycle switch is on, the test does not stop and will continue until an error is detected. If the margin switch is on, the first two-pattern test cycle will be run at low-mar- gin DUT operating voltage and the second cycle will automat- ically switch to high-margin DUT operating voltage. Should both the margin and cycle switches be on, the tests will alternate from low- to high-margin voltage. All voltage and test signals are ap- plied to both ZIF test sockets si- multaneously, but only one DRAM can be tested at a time. DRAM s to be tested can safely be inserted or removed from the ZIF test sockets with the power on. Dynamic RAM DRAM's use multiplexed row and column address inputs; 64K DRAM's require only 7 address lines. 256K DRAM's require 9, and 1-MEG DRAM's require 10. Figure 1 shows a block diagram of a typical 256K x 1 DRAM, and Fig. 2 shows a typical 1-MEG DRAM. Address decoding and ad- dress latches are incorporated in the DRAM. To address the DRAM, row-address data is put on all ad- dress lines and clocked by the ras (row address strobe) signal, then the column address data is put on the address lines and clocked by the cas (column address strobe) signal. DRAM's have a read/write input pin, usually la- beled w, to control the type of op- eration; a data in pin, d; and a DATA OUT pin, Q. Data is held in dynamic RAM by the charge on internal capaci- tors. Since the charge degrades with time, the bits need to be "re- freshed" or row addressed at ap- proximately every 4 to 64 millise- conds. That is typically done by a RAS-only cycle through the row addresses — a normal read or write cycle will also accomplish the refresh. A 1-MEG DRAM may have a "test function" input (tf) at pin 4 that allows it to be tested 4 bits at a time; we do not use that function so the tf input is disabled by tying it to ground. The timing of the address and strobe inputs is critical. A DRAM's "access time," or speed, is the time from ras, which is the PIN ASSIGNMENT 1L 15- 11 13- 12. 1L 10. i_ 1 2 3 A 5 6 J_ Afl Vss D CAS W Q RAS A6 AO A3 A2 A4 A1 AR - A Vcc A7 PIN NAMES A0-A8 ADDRESS INPUT D DATA IN Q- DATA OUT W" -READ/WRITE INPUT RAS - • ■ ■ ROW ADDRESS STROBE CAS COLUMN ADDRESS STROBE Vjc- POWER (+5V) V ss GROUND W- 3D- CAS- N0. 2 CLOCK GENERATOR A0- A1- A2- A3- AH- A5- A6- A7- A8- RAS- — N -yl COLUMN ADDRESS BUFFERS (9) REFRESH CONTROLLER/ COUNTER (8} ROW ADDRESS BUFFERS (9) NO. 1 CLOCK GENERATOR DATA IN BUFFER DATA OUT BUFFER COLUMN DECODER 5 S oo 1024 SENSE AMP I/O GATING "25d fH 1024 r MEMORY ARRAY ^33 FIG. 1— 256K DRAM PIN NAMES AND BLOCK DIAGRAM. DRAM's use multiplexed row and column address inputs; this 256K DRAM requires 9. TABLE 1 Parameter 'rc Random Read or Write Cycle Time Wc Access Time from RAS *CAC Access Time from CAS Wf Output Buffer and Turn-Off Delay w RAS Precharge Time 'ras RAS Pulse Width *CAS CAS Pulse Width 'rcd RAS to CAS Delay Time *A5R Row Address Setup Time 'rah Row Address Hold Time Use Column Address Setup Time *CAH Column Address Hold Time 'afi Column Address Hold Time Referenced to RAS l RCS Read Command Setup Time start of the addressing, to the time at which there is valid data at the output pin d. That is very basically how the DRAM works. Figure 3 shows a read-cycle tim- ing chart for a 256K x I DRAM, and Table 1 explains what the timing symbols mean. Circuit description The DRAM tester uses two volt- age-regulator IC's and only six logic IC's, thanks to the use of two PLD's (programmable logic de- vices) which replace about ten in- dividual IC's. Refer to the block diagram in Fig. 4 and the sche- 34 D Vss W RAS CAS TF A9 AO A8 A1 A7 A2 AG A3 A5 Yoc A4 PI N NAMES A0-A9 ADDRESS INPUT D DATA INPUT Q_- DATA OUTPUT W- READ/WRITE ENABLE RA& ROW ADDRESS STROBE CAS COLUMN ADDRESS STROBE V cc POWER (+5V) V SE GROUND TF -TEST FUNCTION ENABLE MC NO CONNECTION FIG. 2—1 MEG DRAM PIN NAMES AND BLOCK DIAGRAM. Address decoding and address latches are incorporated in the DRAM. x: "RoW ADDRESS mJkZA te; '•sea — ^j "k«H" ^AH / Z7 SCGffiSKSm '«c- (DATA OUT) ]J<'> , > -KIGHZ- "TOd" DATA :> FIG. 3— DRAM READ CYCLE AND TIMING Dl AG R AM f or a 256K x 1 DRAM. Table 1 explains what the timing symbols mean. matic in Fig. 5. An AC power adaptor supplies 9 volts DC at 150 mA to a full-wave bridge rec- tifier made up of D5-D8, which provide automatic input-polarity protection. The 5-volt regulator, IC7, supplies power to everything but the DUT (device under test). DUT power is supplied by IC8, an LM317LZ adjustable regulator which is controlled by logic in the PLD, IC5. For a normal test, IC8 outputs 5 volts to the DUT. Other- wise, 4.5 volts is supplied for the low-margin test and 5.6 volts for the high-margin test. As mentioned before, IC5 and IC6 are TTL PAL devices; IC5 is an MM1/AMD PALI6L8B-2CN low-power, 25-ns device that con- tains the oscillator circuitry for our system clock. Components R15, R16, C12, and C5 are also part of the oscillator. The addi- tional components R14, R5 (the access-time potentiometer), R19 (the calibration trimmer), and R17 (the dial-spread trimmer) form the speed-test circuit which varies the basic system clock. The clock output at IC5 pin 15 is fed into IC6 pins 1 and 6. When the start test switch SI is pressed, a start/reset signal is generated through R7, C2, and R8 which resets 1C2 and IC3 at pin 11; the signal is also applied as an input to IC6 pin 8. Logic in IC6 will gate an output clock sig- nal, designated clki, at pin 14, That drives pin 10 of IC2 which is part of a 24-stage ripple-carry binary counter consisting of two 74HCT4040S (IC2 and IC3). As the clock increments the IC2/1C3 ripple counter, the Q0-Q7 and Q10-Q17 outputs drive 1C1 and 1C4, which are 74HCT257 quad 2-input multiplexers. Multiplexers IC1 and IC4 each select four bits of data from two different sources under the con- trol of a common select input at pin 1. Logic in 1C6 generates the ras signal which is input at pin 3 of IC5, present at pin 3 of test- socket ZIF1 and pin 4 of Z1F2, and is also the input select signal at pin 1 of IC1 and IC4. The out- puts of 1C1 drive address lines A0-A3 and the outputs of IC2 drive A4-A7 of the DUT at test sockets ZIF1 and ZIF2. A 256K DRAM requires an additional ad- dress line, A8, and a 1-MEG DRAM requires two additional address lines, A8 and A9. To gen- to 35 erate the A8 and A9 address lines, Q8. Q9, Q18, and 9 19 from IC2 and IC3 are logic inputs to IC6 which generates the A8 out- RG. 4— DRAM TESTER BLOCK DIAGRAM. The DRAM tester uses only six logic IC's, thanks to the use of two PLD's. put at pin 19 and the A9 output at pin 12. Both PALs (the 16R4 and the 16L8) are rated at 25-ns internal gate propagation delay. That de- lay is an integral part of the sys- tem timing, and is used to determine the timing of the low cas signal at pin 12 of IC5 about 40 ns after ras goes low. The cas signal is applied to the DUT which gates the column-address data after the row-address data has been gated. At the intersec- tion of the row address and col- umn address, we have the selected bit location. Output Q20 (IC3 pin 12) from the 24 -stage ripple counter will determine if the operation will be a write or read cycle in the DRAM. From the start of the test, Q20 applies a low to the DUT read/ write inputs at ZIF1 pin 2 and ZIF2 pin 3. The low signal puts the DRAM in the write mode for the first half of the test, where we cycle through all of the address locations. Note that, as the ripple counter gets to Q20, we have cy- cled through all address loca- tions in a 1-MEG DRAM once. J |» » /» * s -%=^\ * r> ^ * *"- » * g i— rS — s , / ^ |-j ■ ;t5=Si I ' ' * * — ^c— -&=?— r 71..» - if) O Z o cc o -| ill , Jm. j /^j^m m top - side a I *l - ^^^^_ 1*1* "t, "■ • B lv"J ^ B hJ> n fbi L_r*5T *: # v •■uF-ru ■3.35IHCHES- -*\ \- r ■3,35 INCHES - ■*J § TOP, OR COMPONENT SIDE of the DRAM tester PC board. Parts BOTTOM, OR SOLDER SIDE of the board. cc are actually mounted on both sides of the board. 36 < 3 s. -n SB - o 3- g — 3] (D C 3" j, JTJ ffl 2 i5' £. D H (O = ? 33 J7° -? bit 2 -3 9 »i _, tn — 3 < 3 * —1— 2?0tl SI START TEST TDK = " Jl POWIH 9" »g£ <*> ' 2 c » ,S "O 3 <2 Q. w° -* t~ o <& fla oq T w — 3 £S" b 2 w (3 » T3 III -* i o ^> 00 1 us mil' -M- W IB lKtOW INWH — w — t — ** — |J-|V,|, 7I0S Van Jit. am c.i .Iiif tP-Ov ipio S? 1CS v LKS17L v oot — V FM0 . ; 22HG : ■ u—> m 2?0it STUBT.flEBET D 00 12 11 10 09 oa 0? 06 ib 04 03 02 Ql C4 lOftlf ^ Q Q 12 11 10 OS 08 07 06 05 Ql 03. 0! 01 012 013 Mil ms a«. _H!Z_ • ■..-.v-.-i _0JL ..fl'a VL tunem -a^ CYCLE (OPFN.Ofl) OWfJUWHSEl) >I0K (sroi»)aa , -1 MARGIN fcidmBMBBEgT HI 2 IK R13 B1U) C12 ILu' L66I- AVW w o z o IT F o hi D < four times in a 256K DRAM, and sixteen times in a 64K DRAM. The Q20 output is also input to pin 6 of IC5, which will generate a d, n signal, which will determine the data bit (high = 1 , low = 0) ap- plied to the DUT at ZIF1 pin 1 and ZIF2 pin 2. Signals Q0 and Q21 are also applied to IC5 at pins 1 and 7 respectively; Q0 is used to alternate the bit pattern at every other location as it is triggered every cycle or clock time, and Q21 is used to change the pattern from 010101 to 101010 during the second write cycle. Every DRAM location will have both a 1 and a written to it and read back 1 to 16 times per test, depending on the type of DRAM. During the read cycle, the ac- cess time of the DRAM is the time between the ras and D oirr (valid data out) signals, or the time from the first address strobe un- til valid data is at the q output of the DUT. The q output is a three- state signal that switches to a high-impedance mid-logic level when the gas signal goes inac- tive. As each address is cycled through during the read portion of the test, the data bit read out is applied to pin 1 1 of IC5 and com- pared with the expected bit. If the data does not match, an error signal is generated at pin 19 of IC5 that goes to pin 9 of IC6 where the fail output will go high and the clki output will stop. That will halt the ripple counter and make pass/fail indicator LED4 light a continuous red. (LED4 should have been blinking green during the test.) The margin switch S2 is "on" when the contacts are open — that removes the ground from pin 5 of IC5, allowing pull-up re- sistor R4 to switch the input high. The logic in IC5 will then switch the low output from pin 17, which selected a normal DUT operating voltage of 5.0V, to pin 16, which selects a low-margin voltage of 4.5V. Indicators LED1, LED2, and LED3 show which DUT operating voltage is cur- rently selected, and will remain illuminated after an error stop to indicate what operating voltage was selected at the time of failure. The Q22 input at pin 8 of IC5 will switch the low-margin test to high, and select the pin- 18 out- put of IC5, which lights LED3 to indicate a high- margin operating voltage of 5.6V The IC5 outputs that select the appropriate LED indicator also directly control the DUT voltage by applying a ground to R12 via pin 17, R13 via pin 16, or neither when pin 18 (high margin) is se- lected. That affects the adjust- ment pin regulator IC8 which produces V DUT . The cycle switch S3 is "on" when the contacts are open, al- lowing the pull-down resistor R3 to hold pin 7 of IC6 low. The high- est bit in our ripple counter, Q23, is the stop bit. When Q23 goes high, the two-pattern test has run twice. Switch S3 simply pre- vents the high Q23 output from reaching the logic input of 1C6. If you prefer cycling the two-pat- tern test once and stopping in- stead of twice, simply disconnect Q23 from S3 and connect Q22. However, if that is done, the mar- gin test would have to be run with the cycle switch also "on" so that the high-margin test is run. With actual usage, it is con- venient to use the cycle switch most of the time. Just increase the access time until the DRAM fails, then decrease the speed slightly and restart the test to quickly determine the speed of the part. Capacitors CI, C3, C6, and C8— Cll are for power bypass, and Rl is used to limit the cur- rent flow through LED4. Resistor R2 limits the current through LED1, LED2, and LED3, which are discrete red LED's. Using PAL's The programmable array logic device, known as a PAL, was in- vented about 15 years ago at a company called Monolithic Mem- ories, which is now part of AMD (Advanced Micro Devices). The PAL provides a way of combining PARTS LIST All resistors are Vi-watt, 5%, un- Other components less otherwise noted. SI — normally-open pushbutton Rl— 91 ohms switch R2— 330 ohms S2, S3— SPDT sub-mini slide switch R3, R4, R8, R14-R16— 10,000 ohms J1 — 2.1 mm DC power input jack R5— 1000 ohms, linear taper ZIF1— 18-pin ZIF socket potentiometer ZIF2— 16-pin ZIF socket R6, R18— not used Miscellaneous: PC board, four 16- R7, R9, R1 0—220 ohms, 1% pin IC sockets, two 20-pin IC sock- R11— 560 ohms ets, knob for R5, cabinet, 120- VAC- R12— 2000 ohms, 1% to-9-VDC 300-mA wall adapter, R13— 910 ohms solder, etc. R17 — 5000 ohms, 4-turn trimmer Note: The following items are potentiometer available from Startek Interna- R19— 2000 ohms, trimmer tional Inc., 398 NE 38th St., Ft. potentiometer Lauderdale, FL 33334. For infor- Capacitors mation call (305) 561-2211, for or- CI, C3, C6, C8-C11, C14— 0.1 \sJF, ders call (800) 638-8050, FAX monolithic (305) 561-9133. C2 — 1 ^F, tantalum • Complete DRAM tester kit in- C4, C7— 100 n.F, electrolytic cluding programed PAL's (does C5, C12— 15 pF, monolithic not include cabinet and AC Semiconductors adaptor), KIT #DT-90K— $59.95. IC1, IC4— 74HCT257 quad 2-chan- • Complete DRAM-tester kit In- net three-state multiplexer cluding programed PAL's, cab- IC2, IC3— 74HCT4040 12-stage inet, and AC adaptor, KIT binary counter #DT-90CK— $89.95. IC5 — AMD16L8B-2PAL • PC board only, #DT-90PCB— IC6— AMD 16R4A-4 PAL $18.00. IC7-— LM7805 5-vo(t regulator • Programed PAL's — $7,50 IC8— LM317LZ low-power adjusta- each. ble regulator • A factory assembled, cali- D1-D4 — not used brated, and tested DRAM test- D5-D8— 1N4004 1-amp rectifier er — $119.00. diode Add 5% shipping/handling charge LED1-LED3— red light-emitting ($4.00 minimum, $10.00 max- diode, 1 /a-inch diameter imum.) Florida residents must LED4 — red/green 3-lead common- add sales tax. VISA, MC and cathode LED module COD-CASH orders accepted. 38 a number of discrete logic ICs in a single custom-programed IC. The PAL device has a program- mable and array followed by a fixed or array. In the DRAM-test- er circuit we use two very com- mon PALs, a 16L8 and a 16R4. Both are low- power devices, and relatively inexpensive. The use of PAL's results in re- duced parts count and power consumption, a smaller PC board, faster logic, increased re- liability, and, usually overall re- duced cost. A reduced parts count means less-complex PC boards are required, and circuit changes can frequently be made in the PAL program without af- fecting the PC board. On the down side, designing with PAL's does require support tools con- sisting of design software and a device programmer. (Those items are needed by the circuit design- er; the builder does not require those items, as programed PAL's are available from the source listed in the parts list.) The PAL design software provides the link between high-level logic expres- sions and the low-level program- ming details which the device programmer uses. In our circuit, IC5 (a 16L8 PAL) has 10 dedicated inputs, 2 dedi- cated outputs, and 6 com- binatorial input/output pins. IC6 is a 16R4 PAL which has a 4-bit register, a clock register input, 8 dedicated inputs, 4 registered outputs with an output-enable pin, and 4 combinatorial input/ output pins. Both are 20-pin DIP TTL devices, which are one-time programmable by opening fuse links {with an appropriate device programmer) to configure the and and or gates within the de- vice. The PAL devices implement the Boolean logic transfer func- tion, the sum of the products. The and array creates custom product terms, while the or array sums selected terms at the out- puts of the device. Figure 6 shows the pinouts for the 16L8 and 16R4 PAL's with the input/output signals and logic equations used to generate each output. Figure 7 shows the logic diagram for the 16L8 and Fig. 8 shows the 16R4. A PAL is man- ufactured with all "fuses," or con- nections intact. The undesired fuses are blown open by the pro- grammer, leaving only the desir- r- Q01 1 ASEU 2 IHASi 3 CKINAl 4 MTEST l 5 I RDl 6 Q21i 7 Q22j 8 UKINB j 9 GNDI1Q L_. IC5 16LBB-2 cc /" LOGIC EQUATIONS "7 20 jV, 191 ERROR 18HHIGHMARG i 17I1N0RMMARG leilLOWMARG 15DCK0UTA 1-h'din ISi'lGKOUTB 12UCAS 11ID0UT . I DIN CAS HIGHMARG. 0E LOWMARG. 0E NORMMARG. 0E HIGHMARG LOWMARG NORMARG ERROR CKOUTA CKOUTB IQ21 8 100 1 021 & Q0; IASEL S. RAS; MTEST h 022; MTEST & 1022; I MTEST; Q22; IQ22; 022 # IQ22; RD & RAS & (D0UT & 101 N * ID0UT & DIN); CKINA8. 1CK0UTB & l{CKINB & ICK0UTA}; CKtNS & ICK0UTA & l(CKINA& ICK0UTB}; CKIN i 1 Q8J 2 Q9|3 0181 4 019! 5 OK IN! 6 ICYCLf! 7 rstIs ERROR 1 9 GNDH0 IC6 16R4A-4 cc 2DJV, 191 AS 18JASEL 17 [PASS 16|(AIL 15 [{UNUSED OUTPUT} 14t!CK1 13ilRAS 12|A9 11 1 I0E f QUTPUTENABLE" INPUT) I /" LOGIC EQUATIONS *7 ASEL = IRAS; A8 = IRAS & Q8 * RAS & Q18; A9 = IRAS & Q9# RAS & 019; RAS = CKO & ICKIN; PASS.D= IEAIL&IQ18; EAIL.D = ERROR & CKO t RAIL & IRST; CK1.D = IRST 8, CK:1 & IR1L & CYCLE; b FIG. &— PAL PINOUTS AND LOGIC EQUATIONS. 6-a shows the pinouts for the 16L8 and 6- b shows the 16R4. The logic equations are used to generate the outputs. ed logic connections. Assembly The DRAM tester is easy to as- semble. Parts are installed on both sides of a double-sided plated-through PC board mea- suring 3.35 x 3.8 inches. Pro- gramed PAL's, as well as the other parts including the PC board, are available from the source listed in the parts list. The profession- al-looking case you see is also available at extra cost. Parts as- sembly order is not critical, how- ever, it's recommended that you install all resistors first, then di- odes, IC sockets (not including the ZIF sockets), IC7 and IC8, and then the capacitors. Follow Fig. 9 for correct placement of parts. Next install power-jack Jl, and switches SI, S2 and S3. Be sure S2 and S3 are straight so that they will properly fit in the cab- inet openings. Next install poten- tiometers R5, R17, and R19; R5 mounts under the PC board with the pins bent upward to fit the connection holes from under the PC board. The two-color (red/green) LED (LED4) is probably the most diffi- s § 39 16L8 te I3H — 0< 3 4 7 i 1112 mi Ilia BH A« 31 'iS-te iEHc '♦EH*: >EHte: .B-te 'jE-Cs: lEhfc 14 7 1 1112 IB If- 1»» 2124 7TU 31 FIG. 7— 16LS LOGIC DIAGRAM. This 20-pin DIP device Is one- time programmable by configuring the and and on gates within the device. FIG. 8— 16R4 LOGIC DIAGRAM. A PAL is manufactured with all "fuses" Intact. The undesired fuses are blown open by the pro- grammer, leaving only the desired logic connections. CO o o O LU 6 D < EC cult component to install. Be sure to observe polarity; the slightly shorter lead is the red- LED anode ( + ), the center lead is the common cathode (-), and the remaining lead is the green- LED anode. Holding the LED with the shorter lead on your left, bend the center lead at a 90-de- gree angle, snug against the com- ponent body, toward yourself, and likewise bend the other two leads in the opposite direction, spreading them slightly. Align LED4 over the proper PC -board location and bend the three leads down to fit the holes. Check for proper alignment with the cab- inet before soldering. Install LED1. LED2, andLED3. Note that the flat side of the LED's is the cathode. Allow the LED's to stand about % a- inch above the PC board. Install the two 2IF sockets and insert IC1— IC6 into the appropriate sockets. Recheck all component connections and polarities. If you are satisfied that everything looks correct, you're ready to continue. Figure 10 shows a photo of a completed board. Checkout Set R17 and R19 to midpoint adjustment. With no device in ei- ther test socket, connect a 9-volt DC power supply, rated at 200 mA or more (the actual current draw will be about 150 mA), to Jl. (The polarity does not matter as we have a diode-bridge power in- put.) A continuous red should be displayed on LED4, the pass/fail indicator. Using a DC voltmeter, make the following measurements. (Note that a ground pad is located in each corner of the PC board.) These voltages should be within ± 0,1 volt: • IC7 pin 3 (V cc ) should be 5.0V, • With the margin switch (S2) off (slider to right), measure V DUT at TP1. It should be 5.0V. • With the margin switch on, the low-margin DUT voltage indica- tor should be on and TP1 should measure 4.5V. • Place a DRAM IC in the appro- priate ZIF test socket, turn the access-time potentiometer (R5) fully clockwise and press test- switch SI. If the device under test is good and the tester is working properly, LED4 will blink green and, if the margin switch is on, the tester should alternate be- tween high- and low-margin volt- ages. If you do not get a correct indication, try a power off and on reset. Turn on the cycle switch (slider to the left) and the tester should repeat the test without having to press the test button. • When the high-margin voltage indicator LED3 is on, the voltage at TP1 should be 5.6V. If all of the above voltages check out properly, only the "speed" or access-time calibration remains. If you have access to a 100-MHz oscilloscope, look at TP4 with no IC in either test socket. That is the master clock and it should run continuously. Allow the unit continued on page 60 40 DAVID PLANT THERE IS AN OLD AXIOM THAT A MANS work is only as good as his tools — and a good pulse generator is al- ways a good tool to have. Those of us who don't often need pulse generators — the technician working at home on a project, for example — can usually get by with a 555 timer added to a prototype board and used as a trigger. But there's not always enough room on the board to do that, and it is always a pain in the neck. The solution to that problem is our Pulse-Mate, a compact sin- gle-shot and continuous-pulse generator. The easy-to-use de- sign has automatic level setting and positive and negative pulse output. It can be powered from the device under test in the range from 4.5 to 18 volts DC, and has short-circuit protection for itself and the device under test. The circuit Referring to Fig. 1, the circuit basically has three sections. Foremost is the actual pulse gen- erator built around the ubiq- uitous 555 timer, which can be switched from monos table mode (one shot) to astable mode by S2, The value of R8 is selected to create an approximate square wave at mid frequency range and Rll selects the actual rate desir- ed. With S2 in the "astable" posi- tion, Rll and C2 give a range of about 5- to 200-Hz,, which will satisfy most needs. (Note that S2 is part of potentiometer Rll.) If you need to generate higher fre- quencies, a reduction of C2 can bring the range up well above au- dio, but at a loss of the low- fre- quency pulsing which can be quite handy With S2 in the "one shot" posi- tion, pushbutton SI will trigger IC1 for as long as it is held down. The timer's trigger input (pin 2) is held high by Rl to prevent false triggering from hand capaci- tance. When the trigger pin is brought to ground by SI or keyed by the discharge pin (pin 7) in the astable mode, pin 3 goes high to about 3.3 volts (when IC1 is powered from 5 volts). For better circuit stability, power to IC1 is regulated. The second section of the cir- cuit consists of Ql and Q2 which provide the high-rise-time pulse required for digital work. When Ql is turned on by the positive output of IC1. its collector goes low, giving a negative output pulse at the probe if S3 is in the "low" position. The low output from Ql also turns Q2 off: Q2's collector now goes high, which provides a positive pulse at the probe if S3 is in the "high" posi- tion. Transistor Q2 also drives Q3, which drives indicator LED1. Because Q1-Q3 operate at the incoming supply voltage, we strongly recommend that you use 2N4400 or equivalent transistors rather than garden-variety NPN's, as their base-emitter drop is less and they have a faster rise- time. The Pulse-Mate's output waveform is shown in Fig. 2. The probe current is limited to under 5 mA by R6 to protect both the device under test and the Pulse- Mate. The third section consists of a voltage regulator consisting of Zener-diode Dl and Q4. That configuration was used rather than the popular three-terminal devices, such as the 7805, be- cause, when powered from 5 volts, the regulator's internal voltage drop wouldn't leave enough to power 1C1. As the sup- ply voltage increases beyond 6.2 volts, the Zener diode conducts and limits Q4's output to 6 volts for IC1. Construction A parts-placement diagram is shown in Fig. 3, and we have pro- vided the foil pattern for the PC board if you would like to make PULSE-MATE This single-shot and continuous-pulse generator is inexpensive and easy to build, yet it offers automatic level setting and both positive and negative pulses. y z o cr F o LU -I LU o o LED1 O PROBE FIG. 1— THE CIRCUIT HAS THREE SECTIONS: the pulse generator built around the 555 timer, Q1 and 02 which provide the high-rise-time pulse required for digital work, and a voltage regulator consisting of Zener-diode D1 and 04. light, check the LED's polarity and the mounting of Q1-Q4. Pin 8 of IC1 should show 4.5 VDC, Ql's collector should be low (100 mV or less), and Q2's collector should be high (roughly 5 volts). Now check the output pulse by putting S2 in the "on" position. The LED will flash at about 5 Hz, and advancing potentiometer Rll will increase the flash rate to the point where the LED will ap- pear to be continuously lit. If there is no flashing, check the output of IC1 pin 3 for a positive pulse (or a continuous high of about 3.3 volts if the SI inputs are shorted). Final assembly The prototype is installed in a case that fits well in ones hand. However, any enclosure measur- ing 2x4 inches or larger will do. Also, because the case is a hand- held size, the probe is mounted directly to it. If you use a larger case, you may want to mount the probe off-board. The probe is made from a 2- inch screw that is ground to a point after first fitting on an ap- propriate nut; removing the nut will then deburr the screw after the tip is ground down. With one washer fitted over the screw, it is passed through a hole in the case and the nut then secures it in place (don't tighten it right now). By the way, be careful when drill- ing the holes in the case; once a FIG. 2— THE 2N4400 TRANSISTORS have a fast rise-time; here's what the output waveform looks like. your own — there's also a drilled and plated PC board available separately or as part of a kit. With the exception of SI. S3, and the probe, all parts mount on the PC board. Note that LED1 is mounted on the foil side of the board so that it can protrude through the front panel as shown in Fig. 4. (Mount the LED 3 /is- inch above the board so there is room to solder it.) Note that Rll- S2 is also mounted facing up from the foil side. You don't have to connect SI, S3, and the probe at this time. Take a minute to in- spect your work; if everything looks alright, the project is ready for initial testing. Observing proper polarity, con- nect 5 volts DC to the board. With R11-S2 in the "off position. LED1 should be off. Shorting the SI inputs with a clip lead will turn on the LED. If there is no PARTS LIST All resistors are Vi-watt, 5% R1, R2— 27,000 ohms R3, R4— 10,000 ohms R5. R6— 1000 ohms R7-R9-^170 Ohms R1 0—180 ohms R11— 10,000-ohm linear potentiome- ter with switch Capacitors C1, C3, C4— 0.1 u.F, ceramic disc C2— 4.7 LJ.F, 16 voits, electrolytic Semiconductors IC1— LM555 timer Q1-Q4— 2N4400 NPN switching transistor D1— 1N4735 6.2-voit Zener diode, or equivalent LED1 — any color light-emitting diode Other components S1 — momentary pushbutton switch S2— SPST switch (pari of R11 in prototype) S3— SPOT toggle switch Miscellaneous: project case (Radio Shack #270-220 or equivalent), knob for R11, 2-inch screw with washer and nut for probe assembly, red and black insulated alligator clips, rubber grommet, heat-shrink tubing, wire, solder, etc. Note: The following items are available from Project-Mate, 2727 West Manor PI., Suite 207, Seattle, WA 98199 (206) 283-4700: A kit containing a PC board and all parts including probe hardware, grommet, heat- shrink tubing, alligator-clip as- semblies, and front-panel art- work (does not include S1. S3, project case, and knob) is $24.50 plus $2.50 shipping and han- dling. A PC board only is $6.00 plus $2.50 shipping and han- dling. WA residents must add 8% sales tax. h- 2 INCHES HERE'S THE FOIL PATTERN for the Pulse -Mate's single-sided PC board. hole is made, it's there to stay. The leads of R6 should be insu- lated with heat-shrink tubing, 42 RG. 3— PARTS-PLACEMENT DIAGRAM. Note that LED1 and R11-S2 mount on the foil side of the board. + 5V IC1 CLOCK , R1± I0K> ■i 11 — CLK IC1 '/2 74LS74 GND CLR FIG. 4 — IT'S A TIGHT FIT, but you end up with a neat little handheld instrument. Notice how LED1 is mounted on the foil side of the board and protrudes through the front panel. except for the ends; one end is secured between the head of the probe screw and the washer, and the nut can then be tightened. The other end of R6 is soldered directly to the common terminal of S3. Leaving the sharpened tip of the probe screw exposed, cover the length of it with heat-shrink tubing. Connect S3 and SI to the board; the lead length depends on the case you use. The power leads on the prototype are ar- bitrarily 24 inches long. They are soldered to the board then passed through a grommet in the case. Attach the alligator clips to the power leads; use red and black insulators for positive and negative, respectively. The circuit R3 IK #& R2 1K LED2 — LED1 FIG. 5— THIS TEST CIRCUIT uses a 74LS74 positive-edge-triggered flip-flop. Triggering the clock input by hand causes the LED's to change state in an erratic manner. Triggering it with the Pulse-Mate causes the LED's to switch back and forth predictably. board is secured to the front pan- el of the case by the mounting hardware of potentiometer Rll and the wiring to S3. You can also use separate mounting hardware if you like. You may want to make a name- plate as a finishing touch for the project, although it's best to make sure the circuit is working properly before labeling. At any rate, the one on the prototype was made using an aluminum nameplate kit sold by Kepro Cir- cuit Systems, Inc. (630 Ax- minister Dr., Fenton, MO 63026). With it, a full-sized positive is made by transferring black press-on type and other designs to a clear piece of acetate. A blue panel (cut to 1/2" over-size) is contact exposed — like a pho- tosensitized PC board — and de- veloped. The unexposed portions under the transfer patterns are washed away leaving a blue panel with white lettering. Of course la- beling can also be done in a vari- ety of other ways including engraving, rub -on decals, adhe- sive labels, etc. Application The device can be tested using a spare LED. For a positive-pulse test, connect the cathode of an LED to ground and connect the probe to its anode. Pressing SI will light the diode. For a nega- tive-pulse test, connect the LED's anode to 5 volts and its cathode to the probe and press SI to light. (Note that the LED will not light to full brightness in this part of the test because R6 limits the probe current to 5 mA.) If you want to further test the device, build the simple circuit shown in Fig. 5 using a 74LS74 positive-edge-triggered flip-flop. When power is applied, one of the LED's will light. Stroking the clock input with + 5 volts in se- ries with a IK resistor should cause the LED's to change state. (They will, but in an erratic way because it's virtually impossible to generate a clean clock pulse by hand. Now connect the Pulse- Mate's probe (positive mode) di- rectly to the circuit and the LED's will switch back and forth predic- tably. You now have a useful piece of test equipment for trou- bleshooting, project building, digital experimenting, and what- ever else you can think of, R-E 1 43 CO o z O CC I- o UJ — i UJ Q Q < Its quick and easy to add an intercom feature to your existing home telephones. FRANK POLIMENE USE YOUR TELEPHONES AS A HOME INTERCOM SYSTEM INTERCOMS HAVE BEEN AROUND FOR many years, providing a valuable tool in communications for home and industry. Unfortunately these systems either require add- ed hardware or hours of labor in- stalling wires. Responding to demand, many manufacturers have incorporated the intercom as an added feature in their tele- phones. However, replacing your existing equipment is an ex- pense that usually outweighs the justification. The Phone-Corn project we will describe may be used con- currently with any touch-tone phone system, and it provides features that make it practical, easy to use, and inexpensive. Be- cause it connects to your existing telephone equipment, there are no unsightly boxes to clutter up your desk. How it works To engage the intercom at any time, all you have to do is pick up any phone and press the "#" key. That causes one or more alert modules to sound an alarm, sig- nalling other people in the home to pick up a phone. If you answer a call that comes in for someone else, pressing the "#" key will place the call on hold, and the alarm will sound on the alert modules signalling someone else in the home to pick up the phone. That someone else may then re- lease the call on hold by pressing the "#" key or talk to you in pri- 44 FIG. 1— THE PHONE-COM TAKES ADVANTAGE of a device called a "network interface," installed in most newer homes; it is simply a connector box that separates the outside phone line from your internal wiring. vate before answering the call. Since the system is voice oper- ated (VOX), the intercom will dis- engage and return to normal operation after approximately 30 seconds if no conversation is heard. The Phone-Corn takes advan- tage of a device called a "network interface." installed in most new homes over the past 10 years. De- spite the complicated name, it is simply a connector box that sepa- rates the outside phone line from your internal wiring (see Fig. 1). Since a network interface is used by the phone company to deter- mine whether problems are inter- nal or external, a substantial premium service charge may be imposed if you don't have one. Therefore, it is highly recom- mended that one be installed, even if not for this project. Theory of operation Ikke a look at the schematic in Fig. 2. In the stand-by mode, re- lay RY1 is not energized and the only connection to the phone line is the coupling- capacitor CI. The J2-40 FIG. 2— CONTROLLER SCHEMATIC. The SSI202P is a telephone tone decoder whose BCD output is dependent on which tones are present at pin 9. CD 45 PARTS LIST— CONTROLLER All resistors are V*-watt, 5%, un- less otherwise noted. R1— 600 ohms, Vs-watt R2— 1 megohm R3-R7— 56,000 ohms R8— 220,000 ohms R9 — 10,000 ohms R1 0—560 ohms R11 — 10 ohms Capacitors C1— 0.01 u.F, 200 volts, ceramic disc C2, C3. C5, C6, C1 1—0.01 nR 50 volts, ceramic disc C4 — 22 m-R 16 volts, tantalum C7— 0.1 n-F. 50 volts, ceramic disc C8, C9— 1000 n-R 16 volts, ©l©ctrQlvtic C10— 10 jjlF, 35 volts, electrolytic Semiconductors IC1— SSI202P telephone tone decoder IC2 — MC14049 hex inverting buffer IC3— MC14013B dual D-type flip-flop IC4— LM555N timer IC5— 7805 5-volt regulator Q1-Q3— MPSA14 or equivalent Darlington transistor D3, D4, D7, DS— 1N4148 diode D1, D2, D5— 1N4004 diode LED1— red light-emitting diode BR1— 3N246 full-wave bridge rectifier Other components BZ1— 100-dB Mallory Sonalert module XTAL1— 3.58-MHz crystal RY1— DPDT mini relay, 1-amp contacts, 12-volt coil T1— 600/600 ohm audio isolation transformer J1 . J2 — modular telephone jack Miscellaneous: 12-VAC 500-mA plug-in transformer. PC board, project case, etc. SSI202P (IC1) is a telephone tone decoder whose BCD output is de- pendent on which tones are pres- ent at pin 9. The two most-sig- nificant bits (pins 16 and 17) will only be high during a "#" key de- pression. The high on pin 7 of IC4 and pin 4 of IC2 allow Q3 to turn on, thereby energizing the audible alarm. The alarm will re- main on for as long as the "#" key is depressed. Pin 6 of IC2 is now low, which sends a clock pulse to IC3. That transfers the high at IC3 pin 2 to the output at pin 1, which ener- gizes the relay through Ql, R5, m and IC2. The trigger input of IC4, o also being low, starts the VOX- § timer IC4." The clock pulse to IC3 °E is delayed slightly by R7 and C2 o until the output of IC4 pin 3 has rjj enough time to remove the reset 6 signal at IC3 pin 4. When the "#" g key is released, pin 11 of IC3 goes ec high and toggles the output of FIG. 3 — ALERT MODULES plug into any phone jack; the circuit is only active during an "off hook" condition to conserve battery power. PARTS LIST— ALERT MODULE All resistors are 1 A-watt, 5%, un- less otherwise noted. R1— 2.2 megohms R2, R4, R8— 220,000 ohms R3 — 10 megohms (see text} R5— 56,000 ohms R6— 33,000 ohms R7— 680,000 ohms R9 — 1 megohm R1 0—100 ohms (see text) Capacitors C1 — 0.01 (J.F, 500 volts, ceramic disc C2 — 1 n_F, 16 volts, electrolytic Semiconductors IC1— SSI202P telephone tone decoder Q1, Q2, Q4— MPSA14 or equivalent Darlington transistor Q3— 2N5401 or equivalent PNP transistor D1-D3— 1N4004 diode D4, D5—1N41 48 diode Other components B1— 9-volt alkaline or 7.2-volt Ni-Cd battery (see text) XTAL1— 3.58 MHz crystal BZ1— 100-dB Maliory Sonalert module PL1 — 4-wire modular phone plug Miscellaneous: 9-volt battery con- nector, PC board, project case, etc. Note: The following items may be purchased from BCT Elec- tronics, 8742 Belair Road, Bal- timore, MD 21236 (301) 256-0344. MC/ViSA, AX, and DISCOVER accepted. Add $2.50 S&H for each total order. • Drilled, etched, and screened controller PC board — $7.95 • Drilled, etched, and screened alert module PC board— $4.95 • SSI1202P IC— $11.95 • Complete controller kit (in- cludes PC board and all compo- nents except phone jacks and housing) — $39.95 • Complete alert module kit (in- cludes PC board and all compo- nents except phone plug and housing)— $24.95 Network Interfaces may be pur- chased at Radio Shack or most electronic suppliers for around $5.00. B— ^R9 . — R10 — Q2 pitttcooeop-p ' D5 4- h RY1 ' ceb ic.3 C3t ) iw cm-f-Jt } -Re- <"■' ~ C1 ^ 5Z !C P 'C2 Jt f BZ1 Y + eC8^ + nC : J2 -■ — °RED >J1\ >J2/ GREEN jczcji m J .!} YELLOW BLACK 04 ^-R2 — °i\\ C5 ) Jfii— » ' I ICS FIG. 4— PARTS-PLACEMENT DIAGRAM for the controller. It can be installed in any kind of case you can find. 46 FIG. 5— THE FINISHED CONTROLLER BOARD is very neat and compact, so it doesn't take up much space. PHONE LINE PHONE LINE IC4 pin 3 returns to a low state. That places a high on the reset pin (pin 4} and the set pin (pin 8) of IC3, which turns off RY1, re- turning the system to the stand- by mode. Any calls in process are held by maintaining central-of- fice loop current through Rl while in intercom mode. Alert module Alert modules plug into any phone jack (see Fig. 3), and can be powered by either a 7.2-volt rechargeable Ni-Cd or 9-volt al- F1G. 6— PARTS-PLACEMENT DIAGRAM for the alert module. It's good to have at least one on every floor in your home, in a central location. IC3 pin 13 to a low state, prevent- ing the alarm to sound during the next depression of the "#" key (manual turn off). If conversation continues, IC4 is prevented from time-out through C7 and Q2. If con- versation stops for more than 30 seconds, C4 charges to the threshold voltage at IC4 pin 6 and FIG. 7— A FINISHED ALERT MODULE. It can plug into any ordinary phone jack; use a T-connector if you must connect both a phone and an alert module to the same jack. kaline battery. However, the cir- cuit is only active during an "off hook" condition to conserve the battery. During normal opera- tion, there is approximately 50 volts on the phone line. That al- lows base current to flow through Rl which turns on Ql and holds Q2 in an off state preventing power to IC1 and the audible alarm. When the line voltage falls below 10 volts, as evident in an off-hook condition, Q2 turns on, thereby placing IC1 in the stand- by mode. Telephone tones are decoded by IC1 as previously discussed. A "#" key activation will activate the alarm. Diode Dl is important in that it protects IC1 and the rest of the semiconductors from damage when the AC ringing voltage is present on the phone line. If you're using a rechargea- ble battery, charging current is supplied through R3 during on- hook conditions. Construction The Phone-Corn controller is built on one PC board, and the alert modules are built on sepa- rate boards. Determine the number of alert modules you will need including the master con- trol unit. The modules are loud enough to cover approximately 1000 square feet each, even when placed behind furniture. It is rec- ommended that one module be installed in a central location on each floor of your house. Con- struction is straightforward, however, care should be taken when handling the static-sen- sitive decoder chips. We have provided foil patterns for both boards, although the project can be built using point- to-point wiring. Double check your wiring before connecting the modules to the phone line if you don't use the boards. Figure 4 is a parts -placement diagram for the controller board. The finished board, shown in Fig. 5, can be installed in any kind of case you see fit. The values for R3 and RIO de- pend on what type of battery you are using. Use 10 megohms for R3 and 82 ohms for RIO for a 9- volt alkaline battery. If a re- s chargeable battery is used, ^ change the value of R3 to 82K g and RIO to 10 ohms. Any audio 2 47 THE CONTROLLER BOARD is double-sided; here's the component side shown at actual size. w o z o a H O LU _l LU 6 Q < EC SOLDER SIDE of the controller board shown at actual size. transformer with approximately a 500-ohm primary may be used for Tl. Figure 6 is a parts-placement diagram for the alert module, and Fig. 7 shows a finished unit. Again, the board can be installed in any case you like. Follow the red/green color code shown in Figs. 2 and 3 when con- necting the system to the phone line. A "T" adapter may be used if you need to connect additional equipment to the same jack. Velcro strips offer an easy way to secure the modules to a wall. Installation and check out Determine where your network interface is by locating the area where the phone line enters the house. In some cases, the device is mounted on the outside. It is a small box with a short wire loop connecting to a modular jack. Re- fer back to Fig. 1 on how to install a network interface if it's not al- ready present. During the next few steps, your phone system will be inoperative until installation is complete. Disconnect the short wire from the jack on the network inter- -1"/i«IHCHE5- FOIL PATTERN for the alert module, also shown at actual size. face. Connect that wire to J 1 on the main control module. Make sure all phones on the same ex- tension are on-hook, and con- nect the controller to a 12-volt AC source. Pick up a telephone re- ceiver and press the "#" key. The alarm will sound and the LED should be on. You will also be able hear yourself talk through the handset. Hang up the phone. The LED should remain on for approximately 30 seconds, then turn off. Connect the remaining wire from the main control module to the jack on the network inter- face. Pick up the receiver again and initiate a call to determine normal operation. If you are un- able to dial out, the red and green wires (tip and ring) have been re- versed somewhere in the system. Remember that positive phone- line voltage must be present at J2 pin 2. It may be necessary to toggle the "#" key once or twice to get everything going when the sys- tem is first installed or after a power failure. Install the alert modules and determine the cor- rect polarity by measuring a positive voltage at the anode of Dl. Reverse the wires in the mod- ule if it turns out to be necessary. If a rechargeable battery is used, you should allow it to charge for at least 24 hours before activat- ing the system. r-e 48 The SG3524/5/6/7 IC Figure 1 shows the internal cir- cuit of the switching regulator IC SG3524. In that circuit, the os- cillator produces both ramp and pulse outputs. Ignoring the cur- rent limit (CL) and shutdown cir- cuits for the moment, the comparator's output goes high when the ramp exceeds the out- put of the error amplifier. The nor gates then go low. turning the output transistors off. Each nor gate can be high only when its three inputs are low. The oscillator output toggles the flip-flop, enabling one gate, and then the other to respond to the comparator. That action gates one transistor on at a time, providing push-pull operation. The selected transistor turns on at the start of each cycle, and turns off as soon as the ramp ex- ceeds the error signal. At the end IN OUR LAST EDITION. WE EXAMINED the basics of switching regulator power supplies. Now we'll dive into some real-world applica- tions. We'll examine the 3524/5/7 and 3842 IC families in detail, summarize others, and show some typical circuits. In the pro- cess we'll study how to select components for those circuits and learn more about how switching regulator IC's are pro- tected against such problems as startup current surges, under- voltage, and overload. We'll finish up with some basic troubleshoot- ing hints. Lets first start off with an ex- planation of the standard no- menclature used in naming the IC's we will discuss in this article. The first digit "1" indicates full military temperature range of -55 to I50°C, "2" indicates an Industrial temperature range of -25 to 85°C, and "3" is a com- mercial temperature range of to 70°C. Hereafter, we will refer only to the commercial version IC's, with prefix "3. " Keep in mind that all those IC's are also available in military and industrial versions. A suffix of "A," "B." or "C" indi- cates an enhanced version of the IC, which we will discuss in more detail later in this article. Manufacturers may use many different prefixes, some of which include SG— Signetics. SGS-Thomson, Motorola, and Linear Technology. CS — Cherry Semiconductor. XR— Exar. CA— GE-RCA. IC— IPS. LTSG— Linear Technology. LM — National Semiconductor. UC — Unitrode. Motorola, Linear Technology, and Signetics. UD— SGS-Thomson. IP— IPS. LAS — Lambda. Well take an in-depth took at two switching regulator IC jf families, with some applica- tions, and guide you through basic troubleshooting techniques. of each cycle, the oscillator pulse momentarily forces both gates low, protecting against the pos- sibility of both transistors being on at the same time. The current-limit amplifier protects against current over- loads. Its output is an open-col- lector type — open-circuit when high, pull-down to ground when low. The current-limit amplifier and the shutdown transistor can be used to force the comparator output high, shutting down both transistors. Figure 2 shows the SG3524 in a simple DC-DC converter. The oscillator frequency of about 60 kHz is set by R5 andC2. (The flip- flop divides the push-pull output frequency to 30 kHz.) The cur- rent-limit amplifier goes low when its input exceeds 0.2 volts, limiting Rll's current to 2 amps in case of overload or transformer Inside SWITCHING POWER SUPPLIES HARRY L. TRIETLEY HIINPUT-\2/ COMPEMSWION,'^ y CURRENT f .- + LIMIT SENSE - CURRENT _ -LIMIT SENSE SHUTDOWN -t 10 t S' Sfb/WVJ Rr-C 6 1- OSCILLATOR SND 14 (-EMITTER I ' — " — "^ — JL ^-"-x OSCILLATOR -^ 3 t OUTPUT T I I FIG. 1— INTERNAL BLOCK DIAGRAM of the SG3524 switching regulator IC. +28V-«- "*M- -VA—*- R1 C1 .1 R4 5K 16 R5 2K C2 .01 15 INV Nl Vref R T osc SG3524 Cl+ -^ SHUT ROUP DOWN GND 0UMK 12. n R11 0,1 C3 R10 .001 20k: lOOfipf 1 FIG. 2— THE SG3524, TWO SWITCHING transistors, a transformer and a few components create a complete 5-volt push-pull switching regulator. en o 2 O 5 P o LU Q Q < saturation. Transistors Ql and Q2 are used for switching trans- former current. (The on-chip transistors are rated at only 100 mA.) Supply pulses produced by the circuit are filtered by C4. The output of the error ampli- fier is proportional to the dif- ference between the reference input (pin 2) and the feedback (pin 1). If the output increases, the error voltage drops. The ramp then reaches the error voltage more quickly and the transistors ttirn off sooner, until the output is reduced back to 5 volts. Since the feedback voltage and ground are directly connected, input-to- output isolation is not provided. Resistors R6 and R7 limit the current through the internal drive transistors, which are used to switch Ql and Q2. Frequency compensation for closed-loop stability is provided by RIO and C3. Transistors Ql and Q2 should be high-speed switching power transistors rated at least 5 amps and 60 volts. Shottky or fast-recovery diodes should be used for Dl and D2. Because the output is balanced, the trans- former core does not need to be gapped, a small ferrite core will do. At high frequencies, the equiv- alent series resistance (ESR) of filter capacitor C5 is higher than its capaci Live impedance. Low se- ries-resistance electrolytics should be used, preferably capac- itors designed specifically for switching supplies. The enhanced SG3524A Figure 3 shows the enhanced version SG3524A, which is pin- compatible and interchangeable with the non-A version. The en- hanced version adds an under- voltage lockout circuit which disables the regulator until its in- put rises above 8 volts. That holds current drain to standby levels during turn-on, guarding against problems during startup, surges, and brownouts. A pulse- width modulator latch is also added, which eliminates multi- ple pulsing in noisy environ- ments. Set by the comparator and reset by the clock pulse, it can switch only once per com- parison cycle. Further protection is provided by thermal protection circuitry (not shown). Performance speci- fications also are improved — the 5-volt reference is trimmed more closely ( ± 1%) and the error am- plifier's output can swing up to the 5-volt rail. Let's look at one more member of this family, and an application. Figure 4 shows the workings of the SG3525A/7A. The 3525A and 3527A differ only in their output logic; the 3525A is low when off while the 3527A is high when off. (The pinouts of the 3525A/7A do not match those of the 3524 IC series.) Operation is similar to the 3524, but with added features. The oscillator has a sync input, making it easy to lock the fre- quencies of several supplies, eliminating problems with beat frequencies in multiple-supply boards or systems. The shut- down circuit (also included in the 3524A) and soft-start feature simplify the design of protective circuitry, as will be seen in the next application. The totem pole (push-pull) outputs, rated at maximum 500 mA, provide fast, 50 I T OSC-* 3 / T R T -i 6 t V S>J2 osc. UNDER- VOLTAGE SENSOR -5V REFERENCE REGULATOR CLOCK POWER TO INTERNAL CIRCUITRY RAMP COMP-f 9 i- INV ^ INPUTH T l- Nl INPUT/ £y current;' Jy ^ UMIT -„- - CURRENT' Jf ^ LIMIT SENSE I L. COMP rf 1 o Q-, Ql 1 -M6>-Vf a heavier gauge wire, four binlar, uj 4-turn windings of 26 AWG wire 6 are used, with their ends con- es nected in parallel. The control ce (feedback) winding consists of two bifilar, parallel 10-turn 30 AWG windings. Now let's take a look at how an op to isolator can be used in a switching regulator. Optocoupled feedback Optocouplers provide a conve- nient way of coupling isolated feedback. Figure 10 shows a cir- cuit in which the 5-volt second- ary of a switching regulator is controlled. If the output goes above 5 volts, the inverting input decreases below 2.5 volts and the optocoupler's LED current de- creases. That decreases the cou- plers output transistor current, increasing V FB until the isolated output returns to 5 volts. +5V +V FB ' k IC1 input Jr,, COMMON J^.-- ,, Hi | R2 10K R4 10K OUTPUT COMMON R5 10K > D2 * LM385' < -Z.SV FIG. 10— OPT0C0UPLER FEEDBACK al- lows precise control of an isolated output. A wide selection of IC's Once a new IC technology is es- tablished, the offerings multiply as designs advance and the mar- ket expands. Switching reg- ulators are no exception. Voltage mode, current mode, single- end- ed and push-pull IC's cover a wide variety of power levels and user- specific applications. Table 1 summarizes some of the many IC families available. Most of the devices shown can be multiple-sourced. The part number prefixes vary from man- ufacturer to manufacturer, and many offer additional, proprie- tary devices. It's not possible to fully de- scribe all devices in an abbrevi- ated table, but the listing should help direct you to data sheets for IC's to meet your needs. The 8- pin devices tend to be simpler to apply, while the 16-pin and larger IC's generally offer more compli- cated protective and "housekeep- ing" features. The 3524/5/7 and 3842-7 fam- ilies have been fully covered in this article. The 4191-3 family. with its low operating voltage and 200- u-A current drain, is ide- al for battery and micropower ap- plications. Companion micro- power device 4391 provides regulated negative outputs from positive supplies. LT1070 is the only IC in the listing housed in a power IC package. Troubleshooting hints When troubleshooting switch- ing regulators, always begin with the obvious. Check for input power and output shorts, broken wires, defective connectors, sol- der bridges, defective solder joints, bad copper traces, scorched components, and so on. It's surprising how often a good visual inspection can un- cover a problem. Make sure you have a data sheet, pinouts of the control IC, and a circuit schematic, prefera- bly with voltages and waveforms. There is such a wide variety of IC's and operating modes that it's difficult to troubleshoot on an in- tuitive basis. Figure 11 shows a "generic" block diagram, which may help you to think through the circuit function-by-function. When breadboarding tempo- rary components, remember that switching regulators produce fast, high-current pulses. Con- ductor size and lead dress are im- portant. The input filter capaci- tor should be close to the IC , not a foot away If the main source of power is at a distance, add a sev- eral hundred microfarad input bypass capacitor next to the IC. Even though you may under- stand the operation of switching regulators, troubleshooting them can be difficult. The IC and its circuitry perform many func- tions, and the failure of one can cause improper operation of the rest. For example, failure of the feedback circuit may lead to over- voltage, overcurrent, and shut- down by one of the protective features. Is the circuit dead, un- stable or out of regulation? That alone may often narrow the search to one particular part of the circuit. The following hints may help you pinpoint the problem to a specific area of the circuit. After the visual inspection, check the output for shorts or overloads and check the input source, rec- tifier, filter, and transformer. 54 TABLE 1— A SUMMARY OF SELECTED SWITCHING REGULATOR IC'S IC Family Manufacturers* Mode Vorl Output (Single or Push- Pull) Package Supply ■out Max Reference Comments 3524/5/7 CS, ERIC, EXAR, GE, IPS, LT. MOT, NAT, SGS, SIL, SLG, Tl, UNI P-P 16 Pin S-35V 100mA 5 or 5.1V See Article. 3842-7 CS, ERIC, IPS. LT, MOT, SGS, SIG, Tl, UNI 8 Pin 8(or16)-25V 1A 5V See Article. 4191-3 MAX, RAY 8 Pin 2.4-30V 150mA 1.31V Micro power for battery applications, 200 p A quiescent supply current. 4391 MAX, RAY 8 Pin - 4 to - 30V 100mA 1.25V Inverting, micropower for battery applications, 250nA supply at 4V 5560 5562 5561 CS, IPS, SIG 16 Pin 20 Pin 8 Pin 10.5-18V 10-16V 10.5V-18V 40 mA 100mA 20mA 3.72V 3.80V 3.75V Full -featured, flexible. Lower cost, fewer housekeeping functions. 493/4/5 593/4/5 CS, EXAR, GS, IPS, MOT, NAT, Tl, UNI P-P 16 or 18 Pin 7-40V 200mA 5V ^A78S40 MOT, NAT 16 Pin 2.5-40V 1.5V 1 .24V Universal subsystem IC 125/7 IPS. SIL P-P 16 Pin 8-35V 100mA 5.1V 33060/ 34060/ 35060 IPS, MOT 14 Pin 7-40V 500mA 5V 1060 IPS. PLES 16 Pin 20mA into 5V shunt regulator 40 mA 3.7V LT1070 LT 5 Pin Power 3-40V 5A 1.24V Self-contained power IC. "Manufacturers: CS = Cherry Semiconductor, ERIC = Ericsson, EXAR = Exar. GE = GE/RCA'Harris. GS = Gold Star, IPS = Integrated Power Semiconductor, LT = Linear Technology, MAX = Maxim, MOT = Motorola, NAT = National Semiconductor, RAY = Raytheon, SGS = SGS-Thom- son, SIG = Signetics, SIL=Siliconix, SLG = Silicon General, Tl = Texas Instruments. UN! = Unitrode X B, TIMING L 'i v P ABMa [OR SYN TIMING RESISTOR R-C OSCIL- LATOR CLOCK J SOFT-START CAPACITOR I REGULATED INTERNAL SUPPLY INPUT ^CAPACITORi . RAMP L: LOGIC AND orivt GiRcun i: IMi'AFiAIMR WIRED- OR VOLTAGE REFERENCE AND REGULATOR _L T ERROR AMP £* LI EXTERNAL TRANSISTORS \0R FETS SNUBBER L©— ' -OSHUT DOWN ^ THRESHOLD CURRENT SENSOR -Wr- V0LTAGE FEEDBACK I I ,_. I FIG. 11— THIS "GENERIC" SLOCK DIAGRAM of a switching regulator is useful in sorting out the functions which make up the circuit. Sometimes a failure which looks like it might have been caused by output overload is actually caused by a low input voltage. When the input voltage drops, the regulator's duty cycle in- creases, raising the input cur- rent. The increased current may further drag down the voltage, re- sulting in even higher current drain, until an input fuse or cir- cuit breaker trips or something burns out. If the output is dead, check the rectifier and filter, the drive tran- sistors and the output trans- former or inductor. Before replac- ing damaged components check any snubber or surge-suppres- continued on page 64 55 O Z o EC LU c < IE Schools and colleges teach many things — but they don't teach electronic- equipment manufacturing. Most of us pick up that type of knowl- edge through on-the-job experi- ence or through our hobbies, (In fact, hobby magazines like Ra- dio-Electronics probably are the most common teachers of prac- tical design and construction.) However, many engineers gradu- ate from school and enter the work force with little or no prac- tical experience. Recently I had to set up a train- ing center to instruct young engi- neers at my company in basic manufacturing processes. My task was to create a small man- ufacturing factory where stu- dents would build an electronic product. In the process, they would experience every stage of the manufacturing process: in- terpreting engineering draw- ings, buying parts, testing them, building the product, and ship- ping it to the customer. The proj- ect was dubbed the Manufactur- ing Technology Facility (MTF). With a limited budget and lim- ited time in which to teach more than 400 people, I searched for automation aids that would speed up the mundane work without attenuating the man- ufacturing experience we were trying to impart. One area I at- tacked was incoming inspection. In a normal manufacturing plant, parts are bought from many sources. When they arrive, they are tested to ensure they work, because it can cost more than $10 to find and fix a bad SI part in a finished product. The product we built had more than thirty different types of elec- tronic parts, which fell into five groups: resistors, capacitors, di- odes, transistors, and IC's. What I needed was a low-cost way for students to inspect the parts quickly, but with minimum chance for error. The result was what we now call the Component Inspection System (CIS). It incor- porates a capacitance meter, an IC tester, and a computer-con- trolled voltmeter used for testing resistors and diode and tran- sistor junctions. The CIS soft- ware includes a database con- taining each components speci- fications, complete with pass/fail criteria. In addition, the system contains a data-logging function that allows us to maintain a rec- ord of each vendor's quality histo- ry which is useful in selecting vendors. In future articles, we will de- scribe different components of the CIS hardware and software. This time we'll present a $15 two- IC circuit that lets you use your PC as a capacitance meter. Later installments will include com- plete details for building sophis- ticated component and IC test- ers. When space is available, we'll provide the software listings (all of which are in QuickBASIC): compiled programs and source code are also available. PC-based capacitance meter The first project is a capaci- tance meter. It will be incorpo- rated into the next project, a combined voltmeter, ohmmeter, and capacitance meter on a PC board, but it can also be used as a stand-alone test instrument. First let's discuss the details of hardware operation. The circuit, shown in Fig. 1. consists of two ICs: a 555 timer (IC1) and a quad bilateral switch (IC2). The 555 is the heart of the circuit. When configured in the astable (one-shot) mode, the length of the pulse generated at pin 3 is directly proportional to the value of the timing resistor (Rl) and the timing capacitor (C x ). With a fixed timing resistor, the duration of the output pulse will be directly proportional to the value of the timing capacitor. Thus, by connecting a known re- sistor and an unknown capacitor to IC1, triggering it, and then measuring the length of the re- sultant output pulse, we can cal- culate the value of the capacitor. We wanted to obtain an effec- tive meter range of 20 pF to 20 ji.F. To achieve such a wide range, we had to use two different timing resistors — and that's where Ihe 4066 comes in. By driving pin 12 of IC2 high, the IC effectively par- allels a second resistor (R2) with the main timing resistor (Rl). Doing so makes it easier to mea- sure large- value capacitors. With R2 switched in, the effective range of the meter is 0.1 ^F to 20 H,E If the value of the unknown capacitor is less than 0.1 fxF, R2 can be switched out of the circuit (automatically by the software) and the capacitor can then be re- measured. The PC connection The capacitance meter at- taches to your PC via three lines (plus ground) of a standard par- allel port. The autofd signal con- nects to ICl's trigger input (pin 2) to initiate the timing cycle. The ack line from the port connects to ICl's output (pin 3). fn operation, our software drives autofd momentarily low and then high again to trigger IC1. While the PC counts the time interval, the ca- pacitor charges until ICl's inter- nal comparator drives its output from low to high. At that time, ack senses the end of the timing cycle and alerts the PC to stop counting. The software then con- verts the elapsed time interval to a capacitance value. The ds line from the parallel port drives the bilateral switch. Initially, the switch is on. which places R2 in parallel with Rl, and allows you to measure the high range (0.1-20 \iF). If the resul- tant count is less than a specified value, the software switches R2 out of the circuit, obtains a new count, and then scales it for the low range (20 pF-O.lfxF). Because the software depends on a timing loop, it must be cali- brated before use. Calibration consists of making two readings: one accounts for stray circuit ca- pacitance; the other involves measuring a known capacitor to provide a standard. The circuit 56 EXPERIMENTING WITH PC-BASED TEST EQUIPMENT must be recalibrated if the PC's operating speed changes (e.g.. via a turbo mode), or if you con- nect the meter to another PC. Software The simplicity of the hardware is made possible by the software. Although we won't discuss all the details here, there are a few points you should be aware of in the event you wish to modify the software. First, there are two pro- grams. CAP and CAPFAX; CAP is the main program and CAPFAX helps calibrate the software. Both programs are written in Mi- crosoft's QuickBASIC. The soft- ware must be compiled; inter- preters (including BASICA and GWBAS1C) do not run quickly enough to measure capacitors less than 1 |j,F If you want to use the software as is, you don't need to own a copy of QuickBASIC ; a compiled version is available from the author, as mentioned in the parts list. However, to modify the software, you will need a copy of QuickBASIC. Now let's talk about CAR Before doing anything else, the software locates the I/O address of your parallel printer port. That is nec- essary because some cards don't address their printer ports at the standard location (0378h or 888 decimal). In Listing 1, line 16 lo- cates the address and stores it in variable C. (Note that line num- bers are optional in QuickBASIC; they are shown here for reference only.) Variables B and A, which are derived from C, are used to read ICl's output and to operate IC2, respectively. The measuring function be- gins in line 18, which switches in the 100K resistor. The next line initializes the counting variable, X. The next line contains two functions. The first, consisting of the OUT statements, generates a negative-going pulse to trigger IC1. The WHILE/WEND loop then continually increments X until pin 3 of IC1 goes low. The remainder of the program determines if R2 should be switched in, converts the count to a capacitance value, and dis- plays the value in an appropriate form (pF or yiF). Build your own low-cost PC-based test equipment JAMES J. BARBARELLO You use the second program, CAPFAX, to create a data file (CA- PFAX. DAT) that contains infor- mation required by CAP. (CAP- FAX is shown in Listing 2.) Five values are required: zero offset, low factor, high factor, picofarad limit, and microfarad limit. Zero offset is the count obtained with no capacitor connected to the cir- cuit. In operation, CAP subtracts this value from the count ob- > -< (0 57 +5Vi !, ; ►10MIG 14 R2 < 1G0K> 1 2 3 IC1 555 1, 6 ( 1 4. 5 7 IC2 4056 13 12 iVtj 10 T Cv3 ^ SEE - TEXT 4. P1 TQ EBINJEB 14 10 Gl ID, > "•ACK « i nfi AUTOFD tOBI Jjg LISTING 1 FIG. 1— SCHEMATIC DIAGRAM. The ca- pacitance meter consists of two IC's: a 555 running in the astable mode, and an ana- log switch that allows the software to per- form automatic range switching. tained during measurement to eliminate the effects of stray cir- cuit capacitance. Low factor and high factor are reference values that tell CAP what the count should be for a 0.100 u.F capaci- tor in the low and high ranges. Using those factors, CAP calcu- lates the value of the unknown capacitor. Picofarad limit and mi- crofarad limit are values that CAP uses to determine when to switch ranges, and how to format the measured value for presentation on the screen. CAPFAX is used during calibration, and any time you change the circuit layout, PC operating speed, or the PC itself. Construction The circuit's simplicity allows just about any construction method to be used. The easiest approach is to use a solderless breadboard. You'll also need a source of 5-volt DC power; in a pinch you could power the circuit with three batteries in series ( the 4.5 volts produced should be ade- quate to generate the required TTL logic levels.) If you use a CMOS 555, the batteries will last a long time. As shown in Fig. 1, several pins of IC2 must be grounded to en- sure proper switching operation. If those pins are not grounded, the meter may operate erratically. To connect the unknown ca- pacitor, you could insert it di- rectly into the solderless bread- board. For more convenient i 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 IS 19 20 21 22 23 24 25 26 27 23 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 63 70 71 72 73 74 75 76 77 78 R EM ******************* »***. REM** CAP.BAS * REM** V300114 * IgV* **************** A ***** * REM REM** NOTE: THIS PROGRAM MUST BE COMPLIED WITH QUICKBASIC 4,0 PRIOR TO USE REM DEF SEG = 64: DEFINT A-C, I, K: DEFLNG X OPEN "r", 1, "capfax.dat", 50 FIELD 1, 10 AS ol$, 10 AS fl$, 10 AS fh$, 10 AS pf$, 10 AS ufS GET 1, 1 offsetlo = VAL(olS) : FACTOHLO! = VAL{fl$): FACTORHI ! = VAL(fh$) apf = VAL(pf$): auf - VAL(ufS) CLOSE FACTQRLOPF* = FACTOHLOI / 1000000: factorhipf # = FACTORHI! / 1O00000 GOSUB SI: C = PEEX{8) + 256 * (PEEK(9) ) +2: B-C-l: A=B-1 RESTART: OUT A, 64 X » 0: LOCATE 12, 31: PRINT " MEASURING... " ,- OUT C, 2: OUT C, 0: WHILE (INP(B) AND 64): X - X + 1: WEND SELECT CASE X CASE IS > auf measuredvalue - X / LOCATE 12, 31: LOCATE 24, I: LOCATE 12, 36: SOTO SKIPTT CASE ELSE OUT A, END SELECT OUT C, 2: X = o: SELECT CASE X CASE IS > apf measuredvalue measuredval ue LOCATE 12, 31: LOCATE 24, 1: LOCATE 12, 36: GOTO SKI PIT CASE ELSE AA = 0: XX = REDO: OUT C, 2: X = 0: OUT C, 0: WHILE (INF(B) AND 64) IF AA < 5 THEN AA = AA + 1: XX » X -t XX: FOR i = GOTO REDO mean = XX / 5: X - mean LOCATE 12, 31: PRINT SPACES(18); measuredvalue = (X - offsetlo) / FACTORLOPFJ LOCATE 24, 1: PRINT "Lo - pf" ; LOCATE 12, 36: PRINT USING "♦### pf " r measuredvalue END SELECT SKIPIT: LOCATE 24, 62: PRINT SPACESU7); COLOR 7, 0: LOCATE 20, 29 COLOR O, 7: PRINT " n "; : COLOR 7, COLOR 0, 7: PRINT " E " ; : COLOR 7, Tryagain: ReplyS = UCASES (INPUTS (1)) SELECT CASE ReplyS CASE "M" LOCATE 12, 37: PRINT SPACES (6) GOTO RESTART CASE "E" CLOSE : END CASE ELSE BEEP: GOTO Tryagain END SELECT END SI: CLS : LOCATE 3, 23: COLOR 0, 7: PRINT SPACES (35) LOCATE 4, 23: PRINT " PC CAPACITANCE METER " LOCATE 5, 23: PRINT '• (c) 1990, JJ BARBARELLO " LOCATE 6, 23: PRINT SPACE$(35)s COLOR 7, LOCATE 11, 30: PRINT CHRS(222) ; STRINGS(19, 223); CHRS(221) LOCATE 12, 30: PRINT CHR$(222): LOCATE 12, 50: PRINT CHK$(221) LOCATE 13, 30: PRINT CHR$(222); STRING$(19, 220); CHR$(221) RETURN FACTORHI ! PRINT SPACES (18) ; PRINT "Hi - uf " ; PRINT USING "iitf.t uf"; measuredvalue OUT C, 0: WHILE (INP(B) AND 64): X = X + 1: WEND - (X - offsetlo) / FACTORLOl = INT [measuredvalue * 10000) / 10000 PRINT SPACES (18) ; PRINT "Lo - (if; PRINT USING "*.,## uf"; measuredvalue X = X + It WEND 1 TO 100: NEXT i: LOCATE 24, 62: PRINT "Count:"; O: PRINT "easure, or " : O: PRINT "nd ... "; access, you could use a pair of binding posts connected via short lengths of wire. Although doing so adds stray capacitance to the circuit, it can be canceled during calibration. After building the circuit, wire a short cable from a standard DB-25 male connector and four lengths of wire. Connect the ap- propriate pins on the connector to the circuit, and the DB-25 end to your PC's parallel port. Calibration Calibration must be performed prior to using the meter. To per- form the calibration, you need a 58 LISTING 2 PARTS LIST 1 REM** CAPFAX. BAS 2 REM** REVISE CAPFAX.DAT EHTRIES 3 REM** V900114 4 CLS : OPEN "r", 1, "capfax.dat", 50 5 FIELD 1, 10 AS zero?, 10 AS low$, 10 AS highS, 10 AS pf$, 10 AS 6 GET 1, 1 7 LOCATE 1, 30: PRINT "REVISE CAPFAX.DAT FILE" 3 LOCATE 3, 1: PRINT "Zero Offset: •< ; zeroS 9 LOCATE 4, l: PRINT "Low Factor : "; lowS 10 LOCATE 5, 1: PRINT "High Factor: "; higtvS 11 LOCATE 6, 1: PRINT "pF Limit ; " ; pfS 12 LOCATE 7, l: PRINT "up Limit : "; uf$ 13 LOCATE 9, 10: PRINT "Change [Y/H) ? "; 14 GOSUB yesno: IF a$ = "N" THEM GOTO endit 15 z$ - iero$: 1$ = low?: h$ - high?: p$ = pf$; US = ufS 16 getnewones : 1? VIEW PRINT 3 TO 23: CLS : VTEW PRINT IS LOCATE 3, 1: PRINT "Zero Offset; " ,- z$ 19 LOCATE 4, 1: PRINT "Low Factor : '•'; IS 20 LOCATE 5, 1: PRINT "High Factor: "; h$ 21 LOCATE 6, I: PRINT "pF Limit : " ; pS 22 LOCATE 7, 1: PRINT "uF Limit : "; Q$ 23 LOCATE 9, 10: LINE INPUT "New Zero Offset..."; :S 24 IF z$ = "" THEN zS = zeroS ELSE LSET zeroS = zS -1 U " 25 LOCATE 9, 28: PRINT zS 26 LOCATE 10, 10: LINE INPUT "New Low Factor..."; 1$ 27 IP IS = "" THEN IS = lowS ELSE LSET lowS = IS + II 11 28 LOCATE 10, 27; PRINT IS 29 LOCATE 11, 10: LINE INPUT "New High Factor..."; hS 30 IF hS = "" THEN hS - fsighS ELSE LSET highS =- hS t 5 « 31 LOCATE 11, 28: PRINT h$ 32 LOCATE 12, 10: LINE INPUT "New pF Limit "; PS 33 IF pS = "" THEN pS = pfS ELSE LSET pfS = pS + " 11 34 LOCATE 12, 28: PRINT pS 35 LOCATE 13, 10: LINE INPUT "New uF Limit "; u$ 36 IF u$ = "" THEN US - ufS ELSE LSET ufS = uS + " ii 37 LOCATE 13, 28: PRINT u$ 38 LOCATE 15, 10: PRINT "Change (Y/N)?"; 39 GOSUB yesno: IF a$ = "N" THEN GOTO endit ELSE GOTO getnewones 40 endit: 41 VIEW PRINT 3 TO 23: CLS : VIEW PRINT 42 LOCATE 3, l: PRINT "Zero Offset: "; zero? 43 LOCATE +, is PRINT "Low Factor : "; low$ 44 LOCATE 5, l: PRINT "High Factor: "; highs 45 LOCATE 6, 1: PRINT "pF Limit : "; pfS 46 locate 7, 1: PRINT "uF Limit : "; ufS 47 LOCATE 15, 10: PRINT "Save (Y/N)? " ; 43 GOSUB yesno: IF aS = "N" THEN CLOSE : PRINT "NO SAVE": LOCATE IS 49 END 50 PUT 1, 1: CLOSE : PRINT "New Data Saved.": LOCATE 18, 1: END 51 yesno: 52 aS - UCASES( INPUTS (1)) 53 SELECT CASE a$ 54 CASE "Y" 55 RETURN 56 CASE "N" 57 RETURN 58 CASE ELSE 59 GOTO yesno : 60 END SELECT ufS REUISE CAPFAX.DAT FILE lero Offset: 75 .□u Factor : 2195000 Ugh Factor: 25000 )F Linit ! 1000 iF Limit : 10000 Change (Mi)? FIG. 2 — CAPFAX.EXE calibrates and sets the range-switching values for the main pro- gram, CAP.EXE. 0.1 |xF capacitor for which you know the exact value. If you don't have one, use a capacitor marked 0.1 ixFwith the best tolerance you can find (at least 5% or 10%). Begin by executing CAP- FAX.EXE; you'll see a screen like that shown in Fig. 2, except that the five values will all be 0.0. To change values, press Y, and then All resistors are 'A-watt, 5%, un- less otherwise noted. R1 — 10 megohms R2— 100,000 ohms Semiconductors IC1— 555 timer tC2-^tQ66 quad bilateral switch Other components P1 — 25-pin male D connector Miscellaneous: 0.1 uF high-toler- ance capacitor for calibration, sol- derless breadboard, five-volt power source, wire, solder, etc. Note: The following is available from J J Barbarello, RD#3, Box 241 H, Tennent Road, Manalapan. NJ 07726: Compiled version of the software (CAP and CAPFAX), with datalogging, on 5%-inch double-density PC diskette, $8.00. The author will be happy to answer any questions. Please include a self-addressed stamp- ed envelope tor reply. enter the following values as a starting point. • Zero Offset: • Low Factor : 1 • High Factor: 1 • pF Limit : 1000 • U.F Limit : 10000 After entering those values, re- spond by pressing N (No) to the Change question. Respond Y (Yes) to the Save question to create the initial CAPFAX.DAT file. Now connect the circuit to your PC's printer port, but make sure there is no capacitor connected to the test points. Apply power to the circuit and start the software by typing the command CAP at the DOS prompt. The screen will display some value of capacitance, and a count in the lower right hand corner. Press M to measure again. Dis- regard the value displayed, but note the count, which should be between 5 and 100, depending on your particular PC and circuit construction). That value is the zero offset. Next connect the known 0. 1 p.F capacitor and press M to mea- sure. Again, disregard the value displayed, but note the count. Multiply that number by 10 to ob- tain the low factor. For example, if the count is 123456, the low fac- tor is 1234560. Leave the 0.1 u,F capacitor in the circuit. Execute CAPFAX again and en- s 5 55 ter the appropriate values into the Zero Offset and Low Factor fields. Also, change the u.F limit to 1. Save the new data and re- execute CAP Press M to measure. Disregard the value, but note the count, and multiply it by 10 to obtain the high factor. For exam- ple, if the count is 1234, the high factor is 12340. Execute CAPFAX one more time to enter the high factor and change the u,F limit back to 10000. Save the revised data. Use Using the PC-based capaci- tance meter is straightforward. With your PC on and the meter connected to the printer port, ap- ply power to the meter. At the DOS prompt, type CAP and press Enter. Insert the capacitor to be measured, and press M. The val- ue appears in the middle of the screen, and the bottom indicates the range (pF, p.F low, |iF high}, along with the timer count. To end the program, press E. The (xF limit and pF limit fac- tors are used to determine how to format the measured value. If you measure a capacitor that dis- plays 0.00 \iF, but has a count greater than 0, you are in a "no- man's land" between the two lim- its. Execute CAPFAX and in- crease the pF limit factor. Doing so increases the pF formatting range and allows the measured value to be displayed properly. Remember that if you vary the meter circuit or your PC, you should recalibrate the software to maintain accuracy. Next Time In the near future we'll incor- porate the capacitance-measure- ment circuitry into a combina- tion instrument that measures resistance, capacitance, and volt- age. The device allows you to measure resistors, capacitors, diodes, and transistors. Because it is computer controlled, it can be the heart of an automated in- spection system for your shop or business. You can save a lot of troubleshooting time by ensur- ing that the IC's you plan to use in a project function properly before you use them. The last project in this series is an IC tester that al- lows you to verify operation of most 14- and 16-pin TTL and CMOS IC's. R-E DRAM TESTER continued from page 40 to operate a few minutes for max- imum stability, set R5 at 100 ns on the dial, and adjust R19 for a J low clock pulse of 200 ns. Mea- sure the pulse at the 1.0-volt DC level. Next turn R5 fully counter- clockwise; the low clock pulse should be 150 ns. Turn R5 fully clockwise; the low clock pulse should be 300 ns — if not, adjust R17 for the proper "dial spread." FIG. 9— PARTS-PLACEMENT DIAGRAM. The parts shown in color are installed on the "bottom," or solder side of the board — that is, the side opposite that with the Zl F sockets. The R17 and R19 adjustments will interact somewhat, so adjust by small increments, and again calibrate R19 at the 100-ns dial setting with R5 after each change to R17. This adjustment should be easy; both potentiometers should end up somewhere near midrange. If you do not have a scope im- mediately available to calibrate the access-time control, set R17 and R19 to midrange, which should be near calibration, and use the speed test for a relative indication; the function and volt- age margin tests should work fine. All you have to do now is install the unit in an appropriate case and put it to good use. R-E FIG. 10— THE FINISHED BOARD is neat and compact — and, of course, quite useful. 60 ROGER P. NEWELL* A NEW ERA OF PERSONAL COMMUNI- cations may be just over the hori- zon. Imagine the freedom and mobility of making and receiving calls away from your desk and home — In the street, roaming around your office, or even on the golf course. This new service will be provided by Personal Commu- nications Networks (PCN's), which are radio-telephone net- works designed to run parallel to. and compete with, the Public Switched Telephone Network (PSTN) that we are all familiar with. PCN's are intended to provide mobile telephone service with quality and reliability equivalent to wireline. The handset is a dig- ital radio designed to permit pri- vacy and security that meet the standards of a fixed network, with usage rates that are com- parable, or only slighdy higher, than those charged by wireline services. Those advantages can come only if there is a large number of subscribers. A further objective of PCN's is to make effi- cient use of the radio spectrum in order to have as large a capacity as possible. What is a PCN? A generally accepted definition of a PCN is that it is a complete telephone system, running paral- lel to (and competing with) the traditional fixed telephone sys- tem. A PCN consists of pocket ra- dio telephones communicating with fixed base stations in the street or in buildings. PCN's will permit any person to make or re- ceive telephone calls, no matter where he or she might be — at home, on the street, or in the of- fice. Using digital radio tech- niques in combination with a low-cost pocket-sized handset, the PCN will provide a fully mobile service with enhanced quality and all the features and functions of a standard tele- phone system. The underlying idea is that calls should be made to a person, not a place. By as- signing a personal telephone number to an individual (rather •Roger P. Newell is a telecommunications attorney practicing in New York City. He is also editor of Microcell Report, a monthly newsletter on microcell technology. Personal Communication M ETWO R KS Can microcell technology of PCN's make mobile communications truly affordable for everyone? than a line from the phone com- pany's central office] the PCN will be able to ensure that the cus- tomer is always able to be reached in an instant. A more basic system, called Telepoint, operates as a radio pocket payphone, allowing calls to be placed whenever the user is within radio range of a base sta- tion installed by the Telepoint op- erator. When a subscriber wants to make a call, he or she goes within radio range of a public base station installed by the Tele- point operator, opens the hand- set and punches in a personal identification number (PIN). The base station will validate the PIN, and accept the dial information. The call is then extended through the public telephone network. The base station collects infor- mation on the caller's identity (transmitted by the handset) and the duration and distance of the call. The Telepoint company will send a bill to the customer for all calls that happen to have been made during the month. Market demand The desire for communica- tions mobility is strong, A.D. Lit- tle, a respected marketing con- sultant firm, has done market re- search that indicates that a large fraction of the nation's house- holds would gladly subscribe to a PCN. Although market demand depended on the price of the handset and the monthly charges for the service, 40% of all households surveyed were likely to subscribe to PCN's, assuming monthly service charges of $10 per month over the consumer's current telephone bill, and a handset price of $100. When the service premium increased to $40 per month, and handset prices to $250, 14% of all house- holds indicated the willingness to buy PCN service — and that's only the residential market. Be- tween 25 and 35% of all busi- nesses were likely to subscribe to PCN's. A.D. Litde concluded that the interest in PCN's is nearly double that of most other new services. It also found that annual reve- nues from personal communica- tions will range from $10 billion in the first year or two to over $30 billion as the service matures. That's enough to make even a telephone company's mouth water, and explains the current high interest in personal com- munication networks. How it works In some ways PCN's are similar to cellular telephones. In each case, the radio telephone trans- mits signals to a fixed base sta- tion, which then connects the call to another subscriber, or the s public-switched telephone net- ^ work. The fundamental dif- £ ference is that PCN's use ex- 2 61 w D z O c h- O tremely low power for the radio link between the handset and the base station — about 10 milliwat- ts peak power compared with 600 milliwatts for cellular porta- bles, and 3 watts for a car tele- phone. Low power means short range, which would seem to be a severe drawback for a radio tele- phone, but is actually the reason for the current intense interest in PCN's, With a short range, it is necessary to have very large num- bers of base stations, each cover- ing a microcell whose radius is from 200 meters to perhaps half a kilometer. In comparison, cel- lular cells are usually several miles wide. Since the spectrum can be re- used in each of those microcells. PCN's are more spectrum effi- cient than cellular phones, and can provide service to many more people. With such a large capaci- ty, the investment cost per sub- scriber can be kept extremely low. The initial cost of a PCN is ex- pected to be about $300 per sub- scriber, compared with $800 for cellular and $1,600 for wireline networks. In addition, the use of low power also brings manufactur- ing advantages into play. If the handsets broadcast at low power, less power is needed in the bat- tery which means smaller bat- teries, and therefore, smaller terminals and micro-mini- aturized components are used. All that translates into longer talk time, with lower prices available to the public. Spectrum scarcity Microcell technology has the potential to change the way we communicate, and to be a pro- digious revenue-producer for those supplying the equipment and service. Yet PCN's are not springing up all over the land- scape. The reason is that an es- sential element is in short supply — the radio spectrum for handset-to-base transmissions. Virtually all of the technically ap- propriate spectrum has been al- located to users who guard it with the intensity of a bear pro- tecting her cubs. The Federal Communications Commission (FCC} and industry are attempt- ing to find a path through the spectrum thicket. The FCC could, in theory, clear spectrum for a PCN service simply by real- locating a slice away from current users; but past experience has shown that trying to remove a slice of the spectrum is like walk- ing into a buzzsaw. As an alternative, spectrum could be assigned to PCN on a co- primary (sharing) basis, or on a secondary basis, requiring PCN operators to defer to the primary users of the spectrum. But shar- ing leaves the operators unsure of whether their spectrum is suf- ficiently solid to warrant the high investments needed to set up their systems. Either method would involve bloody battles in the halls of the FCC between the spectrum haves and have-nots, and would take several years to resolve. So companies throughout the telecommunications industry are exploring ways to bring to consumers the benefits of low- cost mobile phones, despite the shortage of frequencies. Over 50 applications for experimental li- censes for PCN's and Telepoints have been filed in the U.S., and 13 in Canada, seeking to test a vari- ety of technologies. For example, one company which owns a net- work of interbuilding microwave systems in New York City, will test its use as the backbone distribu- tion network for a PCN. Many ap- plicants, especially the Bell Operating Companies, plan to hedge their bets by testing every- thing in sight. At this time, most of the testers are still in the pre- paratory stage, and that is the reason why few results have been publicly reported. CT2 systems One system, called Cordless Telecommunications, 2nd Gener- ation (CT2), is drawing interest because it uses comparatively lit- tle spectrum. It can be used for Telepoint, residential cordless phones, and wireless PBX's for use in offices. The technique uses frequency-division multiple access (FDMA) to divide four megahertz of spectrum into 40 channels of 100 kilohertz each. The handset checks each of the 40 channels at 750 millisecond intervals, and if it finds another channel with less interference, it will switch to the new channel. When used for residential cor- dless telephones, CT2 has mar- keting advantages over current analog cordless telephones, since CT2 telephones tend to be small- er, have a greater range, and are more difficult to be overheard by one's neighbors. CT2 operates in the 800-1000 MHz range, but only three mega- hertz of spectrum remain unas- signed in that range, and those frequencies were promised to INITIAL SIGNAL F1 F2 F3 H F5 F6 F7 F8 F9 FID «-t BASEBAND °- SIGNAL MIXER J T CLOCK I- DIGITAL FREQUENCY SYNTHESIZER F3F8F5 F7 F3F8F5 F7 HI I,t HI I . t RAPIDLY i CHANGING CARRIER FREQUENCY SEQUENCE MIXER L -O RECOVERED BASEBAND SIGNAL DIGITAL FREQUENCY SYNTHESIZER PN SEQUENCE GENERATOR (3.8.S...7..,) I M FREQUENCY INPUT FREQUENCY I INPUT PN SEQUENCE GENERATOR (3,8,5.7...) TRANSMITTER RECEIVER FIG. 1— A FREQUENCY HOPPING SYSTEM, Pseudorandom noise sequence generators in the transmitter and receiver are used to output the same frequency-hopping sequence. 62 other mobile phone users. An as- signment to a Telepoint service would, however, run into intense opposition from companies al- ready in the market that had hoped to use the spectrum for other mobile uses. CT2 plus Another possibility lies in the use of a more spectrum efficient version of CT. Northern Telecom has proposed that the 3-MHz slices in the 900-MHz band be used for control channels, while actual communication will take place over a 30-MHz band, oc- cupying parts of the spectrum not being used by point-to-point microwave operators in any par- ticular location. Interference with microwave operators would be avoided by use of "smart" base stations which would have the ability to sense which frequen- S(I) cies are being used by microwave channels and would block those frequencies off from the hand- sets. The FCCs Chief Engineer, Dr. Thomas Stanley, presented the possibility that the 4 MHz being considered for allocation to the air/ground telephone service could be shared by microcell users. That may be feasible since the air/ground use is not likely to be heavy in any one location at any given time. Cellular frequencies Dr. Stanley also pointed out that under a recent FCC order, cellular operators are free to use their allotted spectrum for auxili- ary services, providing the pri- mary service of cellular telephony is not affected. Up to 50 MHz of cellular spectrum could be used for a PCN-type service, assuming I i I I 1 I I i I I i I I I i I I i „ a 1 - m J l V 1 gfH + nftl I I 1 t 1 1 1 1 l ^ j u c FIG. 2— SPREAD-SPECTRUM SIGNAL. The carrier signal (a) is modulated by a noise signal (b), resulting in a summed signal, with an expanded bandwidth. DATA INPUT -(XlMIXER MIXER MATCHED FILTER 2 O CARRIER INPUT V FIG. 3 — DIRECT SEQUENCE uses multiple matched filters to reduce noise and increase successful correlation between the receiver and transmitter. Decision logic selects the filter output that is most likely to be correct. that a cellular operator would take precious spectrum away from the higher-priced cellular services. The hitch is that fre- quencies used for PCN's would have to be taken away from the profitable cellular service. Never- theless, NYNEX has announced that it would use a portion of its cellular frequencies to build PCN's in New York and Boston, and is expected to be operational by 1992. Spread spectrum Vast numbers of radio devices operate today with no license at all under the FCCs Part 15 reg- ulations for low-powered devices, including such things as garage- door openers and existing analog cordless telephones. A personal communications system operat- ing at 1 milliwatts or less of radi- ated power would fall under the power limitations of Part 15, and would be allowed to operate at any frequency, but would have to accept interference from existing and future licensed operations, as well as any other Part 15 de- vices. That's a very uncertain foundation for a large invest- ment. One potential solution is to share spectrum through "spread- spectrum" technology. Several experimental PCN's have been set up to explore that option, includ- ing PCN's to be built in Houston and New Orleans by a subsidiary of Millicom, Inc. If successful, they will pave the way to establish a personal communications ser- vice despite the frequency crunch. Results are expected by the end of 1991. Although spread spectrum has been criticized as expensive, and untried in public telephony, it may offer the only hope in the U.S. of getting a PCN service off the ground. Spread-spectrum modulation was originally developed by the military to permit jam-proof and undetectable radio communica- tions. Those are the qualities that permit low-power radio links without interference to or from other radio transmissions. By spreading signal strength over a wide bandwidth, the energy transmitted at any one frequency in the band is low. which effec- g tively reduces the chance of 5 harmful interference. ^ Using spread-spectrum tech- 2 63 DISCOVER EXPERIMENT LEARN ADVANCE ELECTRONICS LASERS CAD-CAM HOME STUDY HEATHKIT HOMEWORKS! Now you can learn beginning to advanced electronics at home, with the same courses used today in the world's top colleges and tech schools, and pay a lot less! You'll learn just what yon want, when you want, at your own pace.The complete story is in our tree catalog, Homeworks by Heathkit. Order yours today, call toll-free: 1-800-44-HEATH (1-800-444-3284) V YES J Please send me a FREE copy of the HonieWorks by Hvatlikit Catalog. Send 10: Heath Company, Dept. 020-056 Benton Harbor, Michigan 49022 Name , Address Citv. Slate I . El! 210 _Zip . Hull Data Systems, Inc. CIRCLE 193 ON FHEE INFORMATION CARD niques, information is transmit- ted over a wide bandwidth using a pseudorandom pattern. User- specific codes are transmitted by each sender to permit the intend- ed receiver to select out the rele- vant transmission. There are two primary methods that are tradi- tionally used to do that; they are frequency hopping and direct se- quence. Frequency hopping is con- ceptually very simple. In trans- mitting a traditional narrow- band signal, the carrier frequen- cy is changed, or "hopped," to one of a great many frequency slots many times per second over a large number of channels. The resulting signal has an expanded hopped bandwidth, which is often in the order of a few hun- dred MHz. The hopping pattern may seem to be an unpredictable sequence, but is actually controlled by a pre- determined pseudorandom noise (PN) generator. The PN sequence generator is used to determine the varying hop slot. The intend- ed receiver and the transmitter simultaneously hop to the same pattern and thus can hear one another. A block diagram of a typ- ical frequency-hopper system is shown in Fig. 1. The pseudorandom nature of the hops has several benefits. Some of those benefits include 1. An eavesdropper will have a dif- ficult time listening unless he has the code which determines the hop pattern. 2. A deliberate jammer will not know where to put his transmit- ter on the band of frequencies since the frequency hopper dodges the jammer. 3. Multiple, uncoordinated fre- quency hoppers will collide only occasionally and therefore will experience only a small amount of interference. Therefore, as more and more users come on, the quality of the signal degrades slowly rather than creating a hard limit on the capacity of a network. Direct sequence, sometimes referred to as "signal shredding, " accomplishes the same goals, but uses different tactics. In the sophisticated technique of direct sequencing, the carrier (infor- mation) signal is digitally modu- lated by the noise signal. Figures continued on page 74 SWITCHING SUPPLIES continued from page 55 sion components. Failure of those will allow high voltage spikes, possibly destroying switching transistors or rectifier diodes. Incidentally, always use identical or approved replace- ment parts for diodes and switching transistors. Slow "garden variety" components will fail quickly, possibly taking other components with them. Before replacing the IC, go through the circuit function-by- function. Try to narrow the prob- lem to one area of the circuit and see if any external components have failed. Is the IC's internal regulated voltage correct? If not, the failure almost certainly is in the IC. Is the oscillator running? If not, check the resistor and ca- pacitor before replacing the IC. Check the soft-start capacitor and the external shutdown in- put, if your circuit has them. Check any compensation compo- nents, especially if the output is oscillating or unstable. If all of the above are working but the output is incorrect, the problem is most likely either the IC or the voltage feedback circuit- ry. A malfunctioning feedback circuit is always tricky to trou- bleshoot, especially in a device as complex as a switching regulator. The best advice is to start at the output and go step-by-step through the feedback circuit. The voltage dividers input-to- output ratio should be correct, even if the voltage isn't. An op- amp or comparator's output should be high if the positive in- put is higher than the negative input; otherwise, it should be low. (Note, though, that the IC connects two amplifiers and other circuitry together in a wired-OR connection. Any one of several problems can bring the error amp's output low] Check any feedback windings and rec- tifiers, optocouplers, and so on. If you still haven't found the prob- lem, replace the IC. Troubleshooting switching regulators can be tricky. Just re- member to go through the circuit step-by step, and keep the basics in mind when you encounter problems. r-e More on toner-cartridge reloading and Santa Claus machines, and some VHF and Microwave resources. DON LANCASTER Every now and then, it seems a good idea to go back over some of our older Hardware Hacker subjects and bring them up to date. Certainly one of the most popu- lar topics ever found on our helpline involves... Toner cartridge reloading PostScript and other laser printers are fast becoming a major industry. There are many millions of units now in use. By far the best and the most popular versions use several styles of laser engines made by Canon, These engines were originally intended to accept a throwaway plug-in cartridge. Inside the cartridge is a source of toner, a photosensitive drum, and a spent-toner holding tank. Played according to the rules, you buy these cartridges for $120, use them for 4000 copies, and end up with a pcr-page toner cost of three cents. As we have seen before, you can easily reload these cartridges your- self dozens of times. Today, you can do so in two minutes for a cost of $6.50 or less, and can easily reduce your per-page toner costs to 0.2 cents per page, a whopping 15:1 cost improvement. Besides saving big bucks on your own printer, you could also resell re- charged cartridges for as much as $15 or even $19 each, as part of an ongoing neighborhood service. There's lots of exciting new things happening in the toner recharging in- dustry, so I thought we might pick up some fundamentals and then bring you up to date on the newest and the best insider secrets. What is toner? Well, it is a mixture of Cusually) black stuff and hot glue. Specifically, toner is a fine powder which has very precisely controlled magnetic, electrostatic, thermal, and visual properties. Most toners are basically a mixture of ferric oxides, polyethylene, and lubricants. Toner starts out in the cartridge's fresh toner tank, A magnetized roller then picks up a very uniform layer of toner. Meanwhile, a nearby pho- tosensitive drum gets flooded with light and then electrostatically charged. It next gets selectively dis- charged by a laser beam, leaving a charge pattern on the drum. As the drum rotates, it passes very near the magnetic roller and the toner selec- tively jumps onto the drum, sticking by electrostatic forces only where you want an image. As your drum rotates further, it passes very close to a highly charged piece of paper, and the toner particles then jump onto the paper. Any re- maining toner that was left on the drum gets scraped off and routed to a spent-toner holding tank. The pho- tosensitive drum then continues on its way for another cycle. Meanwhile, you now have your im- age on the paper. But it is only held there by gravity and by rather weak electrostatic forces. It will easily smear if you touch it. The paper then goes on to a fusion roller assembly. Heat and pressure will melt the toner and force it into the paper, giving you a fairly durable final hard copy. One very important part of most fuser assemblies is the wiper pad. The wiper pad has a small amount of silicon oil on it that both lubricates and cleans up any remaining toner on the pressure rollers. Wiper pads are usually replaced whenever a car- tridge is recharged. Note that just washing a wiper pad is a no-no. Our first rule: Toners vary from ma- chine to machine. Most Canon laser NEED HELP? Phone or write your Hardware Hacker questions directly to: Don Lancaster Synergetics Box 809 Thatcher, AZ 85552 (602) 428-4073 printers use what is known as a black write system, since laser diodes will last much longer this way On the other hand, all but the newest and most expensive copiers use a white write system so that light ends up as white and dark as black. Thus: Copier and Laser-Printing toners must NEVER be interchanged or substituted for each other! There are usually mechanical interlocks that prevent you from plugging a copier cartridge into a laser printer and vice versa. If you attempt to defeat those interlocks, you will end up using the wrong toner. At the very least, that gives you useless copies, and at worst, it can cause serious damage. Similarly, toner chemistry varies from printer to printer, especially be- tween manufacturers. Our second rule: The refill toner you use must be pretested in and rated for the exact cartridge you are refilling. So where do you get refill toner and the wiper pads? My two favorite sources are Don Thompson and Lazer Products. There is also one outfit called Black Lightning that stocks specialty toners for T-shirt and fabric printing uses. The toner industry has its own trade journal, it is called Recharger, and is chock full of supplier ads and useful industry info. There are also at least a dozen recharging associa- tions who do have lots of seminars and conventions. Details on those usually appear in Recharger. The big news today in toner refilling involves new third- party hard coated drums. For some reason or another, the factory stock drums are made needlessly soft. The third-party drums instead are ultra-hard and can easily be used for dozens of reloads. One leading importer of hard drums is CopyMate Products. Let's look at some specific refilling details. Certainly the most popular . cartridges are those used in the 5 Canon CX, SX, and LX engines. Fig- - ure 1 lists many popular laser printers 5 HP MANUAL HP PRINTER 02686-90920 {CX Engine) LaserJet I LaserWriter LaserWriter Plus PS800 33449-90906 (SX Engine) LaserJet II LaserWriter NT PS810 & Turbo LaserJet III LaserWriter NTX PS820 & Turbo 33459-90906 (SX Engine) LaserJet IID LaserJet HID 33471-90904 (LX Engine) LaserJet IIP Personal LW FtG. 1— HERE'S A LIST of all the most popular PostScript laser printers, their equivalent service manuals, and the style of toner cartridges they use. and the specific engine used in each one. Figure 1 also reveals to you the outstanding Hewlett-Packard repair and service manuals involved. The manuals, and all major parts, can be had overnight via VISA/800. For some reason which 1 simply cannot fathom, Apple Computer ab- solutely insists tnat you use the HP w o z o ffi t- o LU 6 Q < NEW FROM DON LANCASTER HARDWARE HACKER STUFF Hardware Hacker Reprints II or III 24.50 Incredible Secret Money Machine 12.50 CMOS Cookbook 24.50 TTL Cookbook 19.50 Active Filler Cookbook 19.50 Micro Cookbook vol I or II 19.50 Lancaster Classics Library 109.50 Enhancing your Apple I or II 17.50 Apple Writer Cookbook 19.50 Apple Assembly Cookbook 21.50 Absolute Reset He S, He 19.50 Enhance 1 or II Companion Disk 19.50 AppleWrlter CB or Assy CB Disk 24.50 POSTSCRIPT STUFF Ask The Guru Reprints I, II or III 24.50 LaserWriter Secrets (lle/Mac'PC) 29.50 PostScript Show & Tell 39.50 Intro to PostScript VHS Video 39.50 PostScript Beginner Stuff 39.50 Pos 1 5c r Ipt Co ok b o o k ( Ado be ) 16.50 PostScript ftef. Manual (Adobe) 22.50 PostScript Program Design (Adobe) 22.50 Type I Font Format (Adobe) 15.50 LaserWriter Reference (Apple) 19.50 Real World Postscript (Roth) 22.50 PostScript Visual Approach (Smith) 22.50 Thinking In PostScript {RelrJ) 22,50 The Whole Works (all PostScript) 299.50 FREE VOICE HELPLINE VISA/MC SYNERGETICS Box 809-RE Thatcher, AZ 85552 (602) 428-4073 CIRCLE 83 ON FREE INFORMATION CARD service manuals to keep your Apple LaserWriter printers alive. As near as I can tell, this is some sort of a top- secret rebate policy. At any rate, you can recognize the older CX cartridges by their large three-inch drums, their red-yellow- green end dial, and their obvious lunchbox handle. While the original LaserWriter and all similar printers using them are rather dated, they do remain useful, especially when print- ing lots of heavier stock. Many used bargains are now cropping up involv- ing these machines. Two sources are Don Thompson and The Printer Works. Non-PostScript laser printers, of course, are an utterly useless ripoff, so be absolutely certain that your used machine can speak genuine Adobe PostScript. Before we begin, note that the pho- tosensitive drums must newer be ex- posed to strong light, or to any light at all over any long period of time. Never get fingerprints on the drum. Cotton gloves are a good idea. Toner is an ultra fine powder that can end up all over everything. It is sometimes best to work outside, possibly wearing a mask. Toner can, in theory, explode a vacuum cleaner, but that rarely will happen. But do be careful. The general steps in refilling any cartridge are fivefold: (1) Remove and discard any waste toner from the spent toner holding tank. Do not reuse the spent toner. (2) Refill your fresh -toner supply tank with a new bottle. (3) Lubricate the drum with a light dusting of Pixie Dust (see below). (4) Replace the oiled wiper felt on the fusion assembly elsewhere in the printer. (5) Update accurate life and service records on a suitable label. Figure 2 shows you those CX refill- ing details. There is really never any To refill an older CX cartridge with the punch-and-go method, you first snap off the cardboard label and then drill a toner filling hole... ~©~ Dfili a F.--.S inch. ho>* using 1 13 ViEt Grip LTn tjit: t aro'uliy diar all ctiipi. A second CX hole is needed to let you empty the spent toner holding tank. This area is found underneath the cartridge... Drill VI inch fwlfl uunj . * M Vni G'ip UniWt; r "•""""" 4 © FIG. 2— THE CX CARTRIDGE is easily recognized by its large drum and its obvious "lunchbox" handle. Here are my "punch-and-go" refilling secrets. 66 The SX cartridge punch-and-go refilling process is similar to the CX, except for the hole locations. The filter hole is shown here... Drill 5)8 inch hole using a*3 Vise Grip Itmbil. caielully clear all chips I ] One or more spent toner drain holes must also get added to the SX cartridge. The plastic is thin, so use a conical step drill... Drill 3/B Inch hole using a 13 Visa Grip Umblt; carefully clear all chips Be curiam thai Ihe new Mole is cantered between Ihe die sink marks! ^^^____/ « FIG. 3 — THE SX CARTRIDGE is wider than it is high, has a small drum, and is the most popular cartridge for the larger 8- PPM PostScript laser printers. reason to tear down a CX cartridge, except to substitute a hard drum. The original factory drums are big enough that you can often get four or five refills as is. For most people most of the time, a total teardown will cause many more problems than it will sol- ve. Remember that your ultimate goal should be minimizing all of your per- page toner costs, not maximizing the number of recharges for each drum. An extra recharge is pointless if it costs the end user more per page to do so. if you absolutely have your heart set on taking a CX cartridge apart, you'll need two special tools. One is a special tamperproof Torx bit. This is EVCO part number #945B700 and is available from Jensen Toots as well as most refilling supply houses. The second is a special pin-pulling tool called a CX C lorn pens tractor and available once again through Don Thompson. Should you use my punch and go method, you will have to drill two holes in the cartridge on your first reload. That is best done using a rather unusual step-drill called a #3 Vise Grip Unibit. They are available from Jensen Tools or from any larger electrical contracting supply house. When used with a variable-speed hand drill, the Unibit cleanly cuts a perfectly round hole in brittle plastic, while producing a single and easily grabbed chip. After drilling the holes, the spent toner is shaken or vacuumed out. You can reseal the hole with plain old Scotch Tape (be VERY careful to get a secure seal!), or else use a nickel Caplug. Your fresh-toner hole is sim- ilarly used to accept a bottle of new toner and then resealed. Figure 3 shows you the SX car- tridge recharging. The LaserWriter NTX is a typical machine that uses this cartridge. The SX cartridges have a one-inch drum and are rather flat looking, being much wider than thick. Should you decide to tear down the cartridge or upgrade to a hard drum, a different glompenstractor is needed having a narrower snout. The details of my punch-and-go re- fill method remain pretty much the same. First time around, you drill a suitable filling and emptying hole. Once again, the #3 Vise-Grip Unibit in a variable-speed hand drill is ideal for this. To refill, drain and discard the spent toner and reseal. Then fill the fresh toner tank and reseal. Figure 4 shews you the newest LX cartridge recharging. The personal laser printers, such as the QMS PS-410, use this cartridge. The LX cartridge is recognized by its small size, an obvious spring, and its "white trim" gears and bearings. No holes are required. To access the tank, pull the two pins by using ChannelLock #357 end pliers. The tank can then be refilled through the existing Caplug. To change the drum or drain the spent toner, remove the four Phillips screws on those nylon drum bearings and pull the drum. The LX cartridge does not need any modifications before any refill, hard drum upgrade, or any spent toner draining... FIRST, remove this spring using a homemade "J" tool. THIRD. Remove the screws to change the hard drum or drain out the spent toner, SECOND, pull these pins to remove the fresh toner tank for easy refilling. But be EXTREMELY careful not to touch the photosensitive drum or expose It to any strong light or ANY light of long duration. FIG. 4— THE SMALLER LX CARTRIDGE is used in the "personal" 4-PPM printers and is easily spotted by its obvious spring and the "white trim." NEVER use copier toner in a laser printer. 2 -4 to 67 Spent toner can be simply vacuumed or shaken out. After a recharge, it's a good idea to very lightly dust any drum with a suit- able lubricant. Many of them are based on plain old zinc sterate. Only don't substitute baby powder since the perfume and oils will do you in. The usual name here is Pixie Dust. Pixie dust is available through most recharging supply houses at very low cost. You can make a "duster" from the toe of a child's athletic sock and a rubber band. Once again, the wiper pad on the fusion assembly should get replaced every time you change the cartridge. You normally keep the old wiper wand and drop a new peel-and-stick oiled nomex felt strip in place. While you can obtain toner-tank re- sealing strips, travel of any kind is extremely rough on toner cartridges. I do not recommend ever moving a car- tridge further than you can gently and personally hand carry it. Nor do I rec- ommend ever swapping your own car- tridges for unknown outsiders. I strictly limit my personal recycling service to a six-mile radius. Yours also should be. Reuse of toner removed from spent-toner holding tanks is not in the least recommended, nor is recycling your own wiper pads. There does remain plenty of "zoo" aspects to toner recycling. Certain irresponsible manufacturers have be- gun some high-profile national "recy- cling" programs which in fact destroy the cartridges rather than recycling them. The hope here is to perma- nently get the cartridges out of cir- culation before they could be refilled and reused. Only an absolute idiot would participate in any program of this sort. If you do nothing else, you can sell your empty cartridges locally for $5 to $10 each, and then contribute as much of the proceeds as you care to to your favorite environmental group. Any salesman that tells you that normal use of a properly recycled car- tridge automatically voids your printer warranty is telling you an outright lie for which they can be criminally pros- ecuted. Some others are literally gold plating stuff that does not in the least need to be gold plated. Yet others substitute shoe polish for proper hard-drum recoating. Those recharge/repair schools run the gamut from outstanding high- FIG. 5— A "SANTA CLAUS" MACHINE for producing large display letters. The poly- ethylene bead from the glue gun is programmed to bui Id up the entire letter one strand at a time. While slow, there are no mold charges and the size and style can be instantly changed. Logos and custom characters are a snap. quality bargains down to outright ripoffs. To tell one from another, ask the school for a list of all previous students in your area. Then call one or two of them. So, you will have to pay careful attention to details. But the toner re- charging industry is fast maturing and now offers all sorts of exciting and cost-saving new hardware- hacking opportunities. A great telephone book I'm often asked how I can usually find helpline names and numbers so fast. Well, I have built up my own re- source data base over the years, and that is where I will often look first. Physically, this is just a big black note- book with lots of stuff that keeps fall- ing out of it. Most of this data base appears in the Hardware Hacker re- prints, and a downloadable and anno- tated selection of the best of the best appears on my GEnie PSRT library as file #80 MYFAVOR.TXT. But the number- two place I always go to is the Electronic Industry Tele- phone Book from Harris Publishing. While it lists for around $50 per year, sometimes you can get a free one or promo copy from a sales rep. This national coverage gem works just like any other phone book, with alphabetical white pages and by-topic yellow classifieds. Their listings are very thorough, and 1 am continually amazed by how often this one volume can solve so many problems. Santa Claus again Several times now, we've taken a look at the new Santa Claus ma- chines that create instant desktop prototypes at a tiny fraction of the time and cost of traditional methods. As we have seen, all the stuff out there so far is primitive, klutzy, and horrendously priced. At least so far. We've also seen some outstand- ing new hacker opportunities here, that range from low-cost desktop prototyping alternatives to offering yourown prototyping service bureaus using the commercial systems. While the best possible desktop prototyping solution remains "none of the above," let's look at a pair of new alternatives. Have you ever played around with your glue gun? While not readily avail- able, you can get polyethylene rods to use as glue sticks. That gives you a method for encapsulating compo- 68 NAMES AND NUMBERS Anderson Power Products GEnie Printer Works 145 Newton Street 401 North Washington Street 3431 Arden Road Boston, MA 02135 Rockvtlle, MD 20850 Hayward, CA 94545 (617) 787-5880 (800) 638-9636 (800) 235-6116 CIRCLE 301 ON FREE INFORMATION CARD CIRCLE 308 ON FREE INFORMATION CARD CIRCLE 315 ON FREE INFORMATION CARD Black Lightning Harris Publishing ElTD Recharger 3870 Lb Sierra Avenue S266 RR 1-87 Depot Road 2057-2 Aurora Road Riverside, CA 92505 Hartland, VT 05048 Twinsburg, OH 44087 (714) 359-8570 (800) BLACK99 (216) 425-9000 CIRCLE 316 ON FREE INFORMATION CARD CIRCLE 302 ON FREE INFORMATION CARD CIRCLE 309 ON FREE INFORMATION CARD Rohm 8 Whatney Caplug Hewlett-Packard/Manuals Irvine, CA 92718 2150 Elmwood Avenue 19310 Pruneridge Avenue (714) 855-2131 Buffalo, NY 14207 Cupertino, CA 94014 CIRCLE 317 ON FREE INFORMATION CARD (716) 876-9855 (800) 752-0900 CIRCLE 303 ON FREE INFORMATION CARD CIRCLE 310 ON FREE INFORMATION CARD Rotary Flight International 5555 Zuni SE, Ste 281 Albuquerque, NM 87108 CopyMate Products Lazer Products (505) 298-9362 20F Robert Pitt Drive 12741 E Caley Avenue #130 CIRCLE 318 ON FREE INFORMATION CARD Monsey, NY 10952 Englewood, CO 80155 (800) 457-0074 (303) 792-5277 Sony Semiconductor CIRCLE 304 ON FREE INFORMATION CARD Cory Laboratories CIRCLE 311 ON FREE INFORMATION CARD 10833 Valley View Street Cypress, CA 90630 LSI Logic (714) 229-4195 CIRCLE 319 ON FREE INFORMATION CARD Box 261, 823 5th Street 1551 McCarthy Blvd Menominee, Ml 49858 Milpitas, CA 95035 Statek (906) 863-9336 (408) 433-8000 512 N Main Street CIRCLE 305 ON FREE INFORMATION CARD CIRCLE 312 ON FREE INFORMATION CARD Orange. CA 92668 (714) 639-7810 CIRCLE 320 ON FREE INFORMATION CARD Crystek Maxim 2351/2371 Crystal Drive 120 San Gabriel Drive Stratasys Ft Myers, FL 33907 Sunnyvale, CA 94086 7411 Washington Avenue S (813) 936-2109 (408) 737-7600 Minneapolis, MN 55439 CIRCLE 306 ON FREE INFORMATION CARD CIRCLE 313 ON FREE INFORMATION CARO (612) 941-5607 CIRCLE 321 ON FREE INFORMATION CARD EVCO National Sandblast Don Thompson PO Box 36339 4421 Prospect NE 23072 Lake Center Drive #100 Birmingham, AL 35236 Albuquerque, NM 87110 El Toro, CA 92630 (205) 822-5381 (505) 883-1151 (714) 855-3838 CIRCLE 307 ON FREE INFORMATION CARD CIRCLE 314 ON FREE INFORMATION CARD CIRCLE 322 ON FREE INFORMATION CARD nents in high-quality plastic or making your own custom connectors. Or of doing plastic casting at a tiny fraction of the usual mold costs. Let's carry this one step further as shown in the crude system of Fig. 5. Say you wanted to produce some large display letters in various styles and sizes. Just take a modified glue gun on a linear stepper and a no-stick base on a second linear stepper, and you should be able to put a plastic bead down that follows the shape of the letter. Repeat the process until the entire letter is created. The host computer traces out the proper path to build up the letter one bead at a time. Admittedly, this is a rather crude system which is limited to thin two dimensional objects. And we haven't properly addressed the third dimen- sion at all. But it is a good starting point that could lead to some exciting new developments. One suitable stepper would be the Hurst model SLS. I've been meaning to work up some more details on this and on Hurst's new EPC-015 control- ler. Maybe in a future column. There is a commercial variation of the "hot glue gun" desktop prototyp- ing method. This is the brand new Stratasys 3-D Modeler. They refer to their process as Fused Deposition Modeling, or FDM. The system starts with a large roll of .020 or .050 diameter plastic or wax filament. The filament is heated just enough to make its outside tacky. The filament is then laid down into an existing pattern in the same way you can do artsy-craftsy stuff with string soaked in glue. A three dimensional object is then built up, literally one string at a time. While they have an elaborate CAD software system based upon NURBS splines, the PostScript lan- guage and any old word processor should be able to do a vastly better s job far faster and much cheaper. $ The FDM method seems es- J peciatly well-suited for modeling con- 5 tainers and other hollow packaging products. But sharp edges appear tricky to do, especially gear teeth. Ultimate costs should be low, since no lasers, fumes, high temperatures, costly materials, or exotic chemicals are involved. The typical speeds ap- proach 1000 inches per minute. One big problem with the system: Some prototypes can end up looking like something that missed hitting the reject bin in the arts and crafts class. Finer filaments can cure this, but build more slowly. I'm wondering if a better prototyp- ing solution might not involve two steps. Homes are usually built in a "rough" and "finish" stage. And ma- chinists often work with near net stock to try and minimize their total production time. And modelers will often build their model first and then superdetail it later. So perhaps the solution is some system that gets the shape pretty near the way you want it quickly and crudely. A second step would then measure and modify what you have to give for your final precision fit and finish. Let's have your thoughts on this. VHF AND MICROWAVE RE- SOURCES ARRL Handbook 225 Main Street Newington, CT 06111 CIRCLE 323 ON FREE INFORMATION CARD Defense Electronics 6300 South Syracuse Way, Ste 650 Engiewood, CO 80111 (303) 220-0600 CIRCLE 324 ON FREE INFORMATION CARD Fair Radio Sales PO Box 1105 Lima, OH 45802 (419) 227-6573 CIRCLE 325 ON FREE INFORMATION CARD Hewlett-Packard PO Box 10301 Palo Atto.CA 94303 (415) 857-1501 CIRCLE 326 ON FREE INFORMATION CARD M/ACom Semiconductor 43 South Avenue Burlington, MA 01803 (617) 272-3000 CIRCLE 327 ON FREE INFORMATION CARD Mini-Circuits Labs PO Box 350166 Brooklyn, NY 11235 (718) 934-4500 CIRCLE 331 ON FREE INFORMATION CARD Motorola 5005 E McDowell Road Phoenix, AZ 85008 (800) 521-6274 CIRCLE 332 ON FREE INFORMATION CARD Nuts & Volts Box 1111 Placentia, CA 92670 (714) 632-7721 CIRCLE 333 ON FREE INFORMATION CARD Plessey Semiconductor 13900 Alton Pkwy, Ste 123 Irvine, CA 92718 (714) 455-2950 CIRCLE 334 ON FREE INFORMATION CARD Radio Research Instruments 584 North Main Street Waterbury, CT 06704 (203) 792-6666 CIRCLE 335 ON FREE INFORMATION CARD to 'O z Q L" h- o LU VHF and microwave resources There are all sorts of interesting things going on in those VHF and microwave frequencies found above several hundred megahertz. Amateur television, weather fax reception, ca- ble services, satellite downlinks, cel- lular phones, sports radar, remote controls, radio astronomy, emergen- cy services, garage doors, al- timeters, instrumentation, microwave ovens, and video links are a few ex- amples of hackable opportunities in the VHF and microwave frequency areas. Unfortunately, all of the hacking rules change in the VHF and micro- wave range. First, you no longer have individual resistors, capacitors, and inductors. Instead, the individual resistance, capacitance, and inductance of each component has to be uniquely taken into account, and often done so in a distributed manner. Circuit strays can quickly become totally intolerable. Tolerances of a few thousandths of an inch can make or break a circuit's performance. Second, testing and measurement often has to be indirect, because Microwave Journal 685 Canton Street Norwood, MA 02062 (617) 769-9750 CIRCLE 328 ON FREE INFORMATION CARD Microwave Product Digest 34 Evergreen Piace Tenalty, NJ 07670 (201) 568-5835 CIRCLE 329 ON FREE INFORMATION CARD Microwaves & RF 611 Route #46 West Hasbrouck Heights, NJ 07604 (201) 393-6286 CIRCLE 330 ON FREE INFORMATION CARD many attempts to directly measure a microwave circuit could severely dis- rupt what you are trying to measure. Not to mention the high frequencies and weak signal levels involved. Most suitable test equipment also tends to be very specialized, arcane, and quite expensive, and hard to justify. Third, VHF and microwave parts can be ridiculously costly, since most of them are aimed at gold-plated low- volume military uses. Fourth, the math, the field theory, Rogers 100 S Roosevelt Avenue Chandler, AZ 85226 (602) 961-1382 CIRCLE 336 ON FREE INFORMATION CARD SGS-Thomson Microelectronics 211 Commerce Drive Montgomeryville, PA 18936 (215) 362-8500 CIRCLE 337 ON FREE INFORMATION CARD Surplus Trader Winters Lane Box 276 Alburg, VT 05440 (514) 739-9328 CIRCLE 338 ON FREE INFORMATION CARD and the advanced technical skills needed to do anything useful at these frequencies goes way beyond elec- tronic fundamentals. A lot of useful microwave information tends to re- quire advanced skills, can be hard to find, and is often classified. And finally, much of microwave de- sign work is far more art than sci- ence. To this day. black magic can be involved, and you either have the right feel for what you are doing, or your circuits simply will not work. 70 For this month's resource sidebar, I have tried to gather together some VHF and microwave stuff you might find of interest. Obviously, you'll want to start with that Radio Amateur's Handbook published by the ARRL. Many of the ham magazines and club activities will also involve the VHF and microwave frequencies. Per a re- cent rule change, certain new ham licenses don't require Morse code. By far the leading surplus house carrying microwave radar goodies is Radio Research Instruments. How- ever, these folks tend to concentrate on whole systems and refuse to show prices in their flyers. Alternate places to look include Fair Radio Sates, Surplus Traders, and in the Nuts and Volts shopper. While utterly ancient, McGraw Hill's MIT Rad-Lab series should still be scrounging around on the dusty back shelves of the larger technical libraries. Volume One in particular, Ridenour's Radar System Engineer- ing has been reprinted a number of times and remains highly useful to this day. Another more recent classic is Merrill Skolnik's Introduction to Radar Systems As with any field, the free trade journals are your foremost day-to-day resource. While there are several dozen, four I've found useful include Microwaves and RF, the Microwave Journal. Microwave Product Digest, and Defense Electronics. Be sure to check out Mini-Circuits Labs for their low-cost broadband amplifier chips, and Plessey for their unusual Satellite Cable and TV Inte- grated Circuit Handbook. They also have lots of info on frequency syn- thesis and high-speed dividers. Hewlett Packard, of course, makes all kinds of microwave components, as well as high-performance micro- wave and VHF test instruments. And Motorola has a wide variety of high- frequency semiconductors and ap- plication notes available. Two other chip sources include SGS and M/A Com, while Rogers supplies printed-circuit materials and dielectrics useful for microwaves. Well, that should be enough to get you started. Please let me know what else you think should be added to our resource files. New tech literature From Sony, there's a new Memory Data Book. They also have lots of great stuff on A/D and D/A convert- ers. From Rohm, there's an Electronic Components Catalog which includes details on their FM stereo broad- casters and lots of other goodies. From LSI Logic, there's a new group of LR64700 video-compres- sion chips that should revolutionize both still- and moving-picture image storage and transmission. I get lots of calls asking about hacker-friendiy sources for custom crystals. Two of my favorite sources are Statek for low frequencies and Crystek for higher frequencies. Both have catalogs, data sheets, and ap notes available. A new detailed bibliography on magnetic refrigeration is available through Jerry Hagen at his Cory Lab- oratories. Our unusual hacker maga- zine for the month is Homebuilt Rotorcraft from the Rotary Flight In- ternational folks, while that free Maxim Engineering Journal has all sorts of semiconductor goodies in it. Especially for audio/ video switches and power supplies that work off a single AA cell. Free samples of Powerpole con- nectors are available from Anderson Power Products Inc. These are both snap-together modular and sexless. They should be ideal for such things as solar panels. An interesting sandblasting cata- log is available from National Sand- blast. This is one quick way to spruce up any metal on your prototypes. Turning to my own products, for the fundamentals of digital integrated cir- cuits, do check into my TTL Cook- book and CMOS Cookbook. Or to pick up all the goodies at once, try my Lancaster Classics Library. We also now have the Hardware Hacker III reprints available, which has the latest and best of all these columns in them. All edited, revised, corrected, and indexed. Finally, I do have a new and free mailer for you which includes dozens of insider hardware hacking secret re- sources. Write or call for info. Our usual reminder here that most of the items mentioned appear either in the Names and Numbers or in the Microwave Resources sidebars. As always, this is your column and you can get technical help and off- the-wall networking per that Need Help? box. The best calling times are weekdays 8—5, Mountain Standard Time. Let's hear from you. R-E DIGITAL VIDEO STABILIZER ELIMINATES ALL VIDEO COPY PROTECTIONS While watching renlal mtwi*s t you will notice an- noying periodic color darkening, color shift, un- wanted lines, Hashing or Jagged edges. This is caused by the copy protec- tion jamming signals em- bedded in the video tape, such as Macrovision copy protection. Digital Video Stabilizer RXII completely eliminates ail copy protec- tions and Jamming signals and brings you crystal dee/ pictures. 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Valley Stream NY t 1580 Unconditional 30 days Money Back Guarantee CIRCLE 178 ON FREE INFORMATION CARD CABLE TV DESCRAMBLER How You Can Save Money ibie Rental Fees Kpg 1 Unit 5+ Jerrold SB w/Tri-BL. $» tTO ..„.„ . . SupcrTri-Bi (IBM). ...... J 109....I75 US Cable will Jerrold 450 combo, S189 ...$139 Beat Anyone's Scientific Atlanta S109.,.,J7J Prl,» SA S53& 1250....$ 19S ... r _V, c All boons are hardcover unless number is followed by a "P" lor paperback. ©1991 ELECTRONICS BOOK CLUB, Blue Ridge Summit. PA 17294-0810 Blue Ridge Summit, PA 17294-0810 D YES! Please accept my membership in the Electronics Book Club and send the 5 volumes listed below, plus my FHEE copy of Delton T. Horn's All-Time Favorite Electronic Projects (3105P), billing me $4.95. If not satisfied, I may return the books within ten days without obligation and have my membership cancelled. I agree to purchase at least 3 books at regular Club prices during the next 12 months and may resign any time thereafter. A shipping/handling charge and sales tax will be added to all orders. Address City State Zip Phone Signature Valid 'or n«w members only Foreign applicants will rcce-ve special OfLterirsg iiiil rucliOrtS. Canada mutf remll m U.S. currency This -twdar aubjael lo occoplancs by the Ssclronies Book Club. RE591 s 5 81 TABLE 1— PC VIDEO MODES Mode NO.* Mode Type** Adapter*** Horiz. Res. Vert. Res. Max. Colors T/G CEVS 40 25 16 1 T/G CEVS 40 25 16 2 T/G CEVS 80 25 16 3 T/G CEVS 80 25 16 4 G CEVS 320 200 4 5 G CEVS 320 200 4 6 G CEVS 640 200 2 7 T CEVSHM 80 25 2 D G EVS 320 200 16 E G EVS 640 200 16 F G EVS 640 350 2 10 G E/VS 640 350 4/16 11 G VS 640 480 2 12 G VS 640 480 16 13 G VS 320 200 256 6A G s 800 600 16 100 G s 640 400 256 101 G s 640 480 256 102 G s 800 600 16 103 G s 800 600 256 104 G s 1024 768 16 105 G s 1024 768 256 106 G s 1280 1024 16 107 G s 1280 1024 256 In hex " T = Te> *•« c = cc idecimal :t only, G = Graphics only, T SA, E=EGA, V=YGA S= /G - Bit- mapped text Super VGA, M = MDA, H = Her cules w o z o DC h- o w _i uj 6 Q < built-in gray-scaling capabilities, so you can plug either a monochrome or a color monitor into a given adapter, and your software will run un- changed. Beyond VGA VGA is nice, but it's not the end of the story. As soon as IBM introduces a product to the PC market, other vendors quickly seek to improve it, and VGA was no exception. Third- party vendors quickly pushed resolu- tion up to 800 x 600, 1024 x 768, and other intermediate resolutions. At first, each vendor implemented its hardware and software in different ways. Soon, however, the industry re- alized it was headed for chaos, so the Video Electronics Standards Associ- ation (VESA) formed to define stan- dards for beyond-VGA modes, VESA membership includes virtually all manufacturers of monitors and video adapters — except IBM, Hercules. Compaq, and a few others. What VESA has done is stan- dardize horizontal and vertical sweep frequencies, and assign BIOS mode numbers for standard resolutions, as shown in the bottom half of Table 1 . These standards should make it easi- er to write software drivers and as- sure customers of compatibility. Beyond Super VGA Super VGA is really nice — but it's not the end of the story either. The reason is that the VGA architecture is dumb, dumb, dumb. It requires the host CPU to do all of its bit twiddling. To draw a line, the host CPU must write directly to memory, often a sin- gle memory location for each af- fected pixel. At low resolution, performance may not be affected much by letting the host CPU do ev- erything. But as resolution increases, the host CPU must spend an increas- ing proportion of its time tending to the screen, which slows down the rest of the system. Wouldn't it be nice if the host CPU could delegate some responsibility and free itself up for other types of tasks? Well, it can. The trick is to put some intelligence on the video adapt- er card itself. Then the host CPU can tell it, "Draw a line from 0<1, YD to (X2.Y2), and let me know when you're done," and meanwhile go on and do something else like tend to a background print spooler, recalculate a spreadsheet, reformat or spell- check a document, or accept charac- ters from a modem. IBM's first entry in the world of intelligent graphics adapters was the 851 4/A, introduced shortly after the VGA in 1987. Unfortunately Cfor IBM), the company shrouded the 8514/A in a veil of secrecy by not publishing hardware-level specs, as the company had for all previous adapters. So third-party vendors had to reverse-engineer on -board IC's, which slowed development of clones and software support, hence accep- tance in the market. In addition, the 8514/A is really a half-breed that pro- vides only partially intelligent control over the video buffer. Further, IBM's 8514/A produces an interlaced dis- play that many people (including me) find visually straining. The main justi- fication for interlaced monitors is that they are slower, hence cheaper, than non-interlaced monitors. Although the 8514/A provides comparable res- olution and better performance than the better Super VGA boards, it seems unlikely that it will ever attain the importance of VGA. Beyond beyond-Super-VGA While IBM floundered, Texas In- struments released the 34010 graph- ics coprocessor and a robust, general-purpose software interface to it. The 34010 is a full-fledged mi- croprocessor with a powerful instruc- tion set containing many graphics- specific commands. At first, support for the 34010 was sparse, but with the increasing popularity of graphical user interfaces, support is increas- ing, competition is heating up, and board prices are falling. (See the sidebar for a discussion of Hercules' new 34010 board.) Of course, IBM doesn't give up without a fight. In the fall of 1990, Big Blue introduced its next-generation video controller, the Extended Graph- ics Array CXGA). XGA differs from 8514/A in several significant re- spects. First, it's 100% VGA-com- patible. Second, it's more intelligent 82 R-E Computer Admart GETTING THE MOST FROM YOUR PRINTER Getting The Mo*t From Your Printer BP181— It is probable that 80% of dot-ma- trix printer users only ever use 20% of the features offered by their printers. This book will help you unlock the special features and capabilities that you probably don't even know exist. To order your copy send $6.95 plus St. 50 for shipping in the U.S. to Elec- tronic Technology Today Inc., P.O. Box 240, Massapequa Park, NY 11762-0240. Rates: Ads are 2K"x2%". One insertion S995 each. Six insertions $950 each. Twelve insertions 5925 each. Closing date same as regular rate card Send order with remittance to Computer Admart, Radio-Electronics Magazine, 50Q-B Bi-County Blvd., Farmingdale, NY 11735. Direct telephone inquiries to Ariine Fishman, area code-1 -516-293-3000. FAX 1-516-293-3115. Only 100% Computer ads are accepted (or this Admart. | ICs PROMPT DELIVERY!!!! SAME DAY SHIPPING (USUALLY) OUANTTTY OME PUCES SHOWW 10* WAR. J. 1 »1 1 DYNAMIC RAM K^l iM Bnnrrt Inr nn 1 .1 Hire S160.00K s IflSIMV 4Mx9 80 ns 240.00 m ~ Bd3 SIMM 1Ml9 60 ns 63.00 p : ■ga simw (Mx9 80 ns 54.00 P 1 H 4 Mbit 4Mx1 80 ns 3000 E i HI'- Mbit 80 ns 4s.no m ' KM1 Mbit 80 ns 5.75 m - RE>412S6 256Kx1 100 ns 2.I0B 1 94125C 256Kx1 120 ns l.9Spi ■ 442 5« 256K*l 100 ns s.gs m j H44S4 64Kx4 100 ns 1 .95 m i EPROM ■P P|sl27C4001 512KXS 150 ns $55.00 I* ■^S27C1000 i.'BK.f: 150 ns 16.50 pfc ■ 27C512 64Kxa 120 ns 7.50 ■ 9 2725I 32Kx8 150 ns 5.00 ■ *J27128 250 ns 3.40 ■ STATIC RAM ■•£■ 1 Mbit £'£:-:■ :l: 100 ns sis.ool BililG2256LP 100 ns 6.50fl I OPEN 6' i QA ys.7» tu 10 r i SMPVIAFEOEXONSAT 1 1 SAT DEL OH WflSlcrCirrJ VIS. A Of UPS CA- 3MCOO 1 FEt-ES OflOfiflS MICROPROCESSORS JNUMITED. INC 1 r; ! ;: f ,i p Bit LaaSesirflfl«"s , :>', ^ 1 fr. M 1:TX 1 k No minimum §t&6i- p>uia -tw 1 COO AVAIL ABLE Ihfpnj ■ru^ino* PT68K4 68000-16MHZ *EGA/VGA* *fflGH DENSITY DRIVES* • 4 MB of onboard DRAM • 4 RS232 + 2 Parallel Ports • Floppy Disk Controller • 7 XT Expansion Slots 16 MHZ Kits from $189 Assembled Boards from $499 Professional OS9/68000 $299 Peripheral Technology 1480 Terrell Mill Rd. Suite 870 Marietta, GA 30067 404/984-0742 CIRCLE 61 ON FREE INFORMATION CARD CIRCLE 189 ON FREE INFORMATION CARD than the 8514/A, so it should be fast- er. Third, it runs only on Micro Chan- nel PS/2's, which limits its potential market. Fourth, it requires a 386 or 486 to run, which also limits its poten- tial market. Fifth, like the 8514/A, the XGA produces an interlaced display, so it's subject to flicker. At present it's hard to see, given the falling prices of 34010 boards, how the XGA is going to have any significant impact on the market. CFor a technical overview of the XGA, see Jake Richter's article in the February issue of Byte.) Color and resolution In this discussion so far, I've mostly ignored the issue of color. CGA al- lowed a maximum of four in its low-res mode: EGA increased the maximum to 16; and VGA increased the max- imum to 256, but with that many col- ors the resolution dropped back to the low-res CGA level. (Even so, 256- color images at that resolution are much more realistic than 16-co!or im- ages at much higher resolutions.) In the meantime, the Super VGA boards developed support for 256 colors at all resolutions up to 1024 x 768. 256 colors are nice— but it really takes about 16 million C2 24 ) colors for true photo-realistic imaging. Special workstations have had that type of imaging for awhile, as have high-end Macintoshes. But now these "true- color" boards are drifting over to the HERCULES' GRAPHICS STATION CARD You can sum up the 34010-based Hercules Graphics Station card in three words: speed, speed, speed. I tested it in a 33-MHz 386 under Win- dows 3.0, and it roughly doubled screen redraw speed. For example, Word for Windows ran about as fast as a text-mode word processor under DOS. The card provides lull hard- ware-level VGA emulation, a 512 x 480 true-color mode, and a 1024 x 768 256-color mode. Sample true- color images included with the board are breathtaking. The board is well- built, and comes with drivers for Win- dows 3.0, AutoCAD 11, and others. Installation and documentation are a bit rough, and I encountered the rudest technical-support person I've run across in years while ironing out a driver upgrade problem. But after overcoming those hurdles, I really enjoyed using the Hercules Graphics Station Card. It really puts some zing into Windows, and the company ex- pects to improve performance as Windows learns how to take advan- tage of intelligent graphics sub- systems. Tfie card lists for about $1000, but is available through mail-order chan- nels for about $700. Highly recom- mended for heavy Windows and AutoCAD users. Hercules Computer Technology, Inc., 921 Parker Street, Berkeley, CA 94710. (415) 540-6000. CIRCLE 41 ON FREE INFORMATION CARD PC environment. However, they're very expensive ($4000 and up). What's ahead HDTV continues to loom just beyond the horizon. In terms of the way I spend my time, I don't much care about it for entertainment, but I do care about it in the way it could affect computer- monitor pricing if the technologies converged. The least- expensive 19" 1024 x 768 monitors now go for about $1500. but if the same technology were used in HDTV displays, that price could easily drop by two thirds. Of course, a strong U.S. presence in HDTV would do much for our economy, the trade defi- cit, semiconductor manufacturing,... you name it. Let's hear it for a strong U.S. presence in HDTV! What to buy There is no reason not to buy VGA. During the past year the price of a plain VGA adapter card has dropped to about $100, and monochrome VGA monitors are available for under $150. Color VGA monitors now go for about $350, SuperVGA monitors for about $500, and Super VGA board/monitor combinations can also be had for about $500. Bought as part of a system, color VGA typ- ically adds about $300 to the overall cost. Don't buy anything less than ^ monochrome VGA. and if you run $ Windows, aim for 800 x 600 Super £ VGA as a minimum. R-E S 83 MARKET CENTER FOR SALE w o z O DC F O LU _1 ID 6 a < en 84 FREE cable and satellite descrambler plans. Send self addressed stamped envelope. MJM INDUS- TRY, Box 531, Bronx, NY 10461-0208. TUBES; "oldest," "latest." Parts, and schematics. SASE for lists. STEINMETZ, 7519 Maplewood Ave., RE, Hammond, IN 46324. ENGINEERING software, PC/MSDOS. Hob- byists — students — engineers. Circuit de- sign and drawing, PCB layout, Logic simulation, FFT analysis, Mathematics, Cir- cuit analysis. 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Tocom 5503 w/r $199,00 10-$189.Q0 20-$1 75.00, SYL 4040 replaces Jerrold 400-DtC w/r $125.00 10-S1 00.00 2O-S75.00, 4040 with internal tri-bi su- perfast w/r $165.00 10-$150,00 20-S125.00 with in- ternal S-A descrambler $165.00 10-$150.00 20-$125.00, with internal Hamlin descrambler $125.00 10-$100.O0 20-$75.00. MLD-1200, SA3B, Super-Tri-Si, same low prices. Zenith Z-TAC $225.00 COD. OK MOUNT HOOD ELEC- TRONICS (503) 253-0459. DESCRAMBLERS, wholesale prices, examples X-12 Oak descrambler $49.00, RTC-56 combo $135.00, Tocom 5503 combo $199.00, 4040 SB combo $125.00 S.A.C., info (702) 647-3799, Orders 1 (800) 622-3799. ' Quality Microwave TV Antennas WIRELESS CABLE ■ IFTS - MMDS ■ hiuleur TV Ultra Hrgh Gain 5M>(+) • TiMibU 1.9 la 2.7 Ghi. • 36-Channd System Complete $149.95 • '2 -Channel System Complete S1 14.95 • Call or write (SASE1 for "FREE" Catalog, PHILLIPS-TECH ELECTRONICS P.O. Box 3533 • ScDttsdile, AZ 85252 £ (E02) 947-7700 |$3.00 Credit all plniieordEril WARRANTY .MaileiCard * Vlii ■ COD'i • Uaantity Pricing PARTS at bargain prices. Free flyer: NETWORK SALES, 90 Turner, Elk Grove. IL 60007. (708) 952-1115. SECRETS of data encryption standard $7,00, se- cure microprocessors explained $5.00, "smart cards" explained $5.00. Details free. Sent first class. BBB, Box 637, Polk City, FL 33668. ADULT video tapes 90 min. VHS current color vid- eos assorted titles 1 — $10.00 3 — $25.00. Free shipping. STRINGSOFT, Box 915-R. Old Bridge, NJ 08857. CABLE TV converters and descramblers. We sell only the best. Low prices. SB-3 $79.00. We ship C.O.D. Free catalog. ACE PRODUCTS, PQ Box 582. Dept. E. Saco. ME 04072. 1 (800) 234-0726. PR I N TE D circu it board s etched & d ri I led . Free deliv- ery. K& F ELECTRONICS, INC., 33041 Groesbeck, Fraser, Ml 48026. (313) 294-8720. CABLE descramblers (Jerrold) from $40.00. Tocom VIP test chip. Fully activates unit. Also Zenilh lest board. Fully activates Z-Tacs. $50.00. Call (213) 867-0081. TV. notch filters, phone recording equipment, bro-. chure $1,00. MICRO THinc, Box 63/6025. Mar- gate. FL 33063. (305) 752-9202. CB RADIO OWNERS! We specialize in a wide variety of technical information, parts and services for CB radios. 10-Meter and FM conversion kits, repair books, plans, high-performance accessories. Thousands of satisfied customers since 1976! Catalog $2. CBC INTERNATIONAL P.O. BOX 31500RE. PHOENIX, AZ 85046 TECHNICIANS. The ultimate tesl lead, jumper ca- bles with switch $1 4.95 each. MHA, PO Box 152797. San Diego, CA 92195. INFRARED remote controlled RF and A/V switches. Write or call to order or get additional information about Infracon's complete MediaMaster series of infrared conlrolled switches: MediaMAster RF-5X2 and MediaMAster AV-4X4. INFRACON, PO Box 1205, Richardson, TX 75085-1205. (214) 437-3366. PHOTOFACT folders under #1400 $5.00. Others $7.00. Postpaid. LOEB, 414 Chestnul Lane, East Meadow, NY 11554. Try the trhujlrtiniris bulletin board system (RE-BBS) 516-293-2283 The mare you use it the more useful it becomes. We support 300 and 1200 baud operation. Parameters: 8N1 (8 data bits, no parity, 1 stop bit) or 7E1 (7 data bits, even parity, 1 slop bit). Add yourself lo our user Files to increase your access. Communicate with other RE readers. Leave your comments on RE with the SYSOP. RE-BBS 516-293-2283 CABLE TV DESCRAMBLERS! BARGAIN HEADQUARTERS! •JERROLD 1 " 'TOCOM -HAMLIN •OAK 'ZENITH • SCIENTIFIC ATLANTA 6 month warranty! We ship COD! Lowest retail/wholesale prices! FREE CATALOQ: Global Cable Network 1032 Irving St. Suite 109 S.F., CA 94122 NO CALIFORNIA SALES!!! ORDER TODAY! 800-327-8544 CABLE TV DESCRAMBLER LIQUIDATION! FREE CATALOG! Hamllo Combos S44. Oak W35B $60 (mln. 5), etc. WEST COAST ELECTRONICS For Information: 818-709-1758 Catalogs & Orders: 800-628-9656 THIS IS A BOLDFACE EXPANDED AD. IF you like this format the cost is 55.65 per word. CABLE TV TB-3 (Tri-Bi) or SA-3 Quantity Prices 10 20 $48. $43 Each 50 Each 100 5pjy H 3>*50i Each Each Hours open 10:00 am to 4:00 pm Eastern time Minimum order 5 units 55.00 ea. Dealers wanted. We ship COD. King Wholesale 1-800-729-0036 Fax number 6173400053 'Wo one beats the King's prices!" DESCRAMBLERS 5 85 Cable Descramblers New Auto Tri-Bi guaranteed no flashing $165,00 SB-J ..,_. S99.00 ZENITH SUPER TRIMODE SIO9.0O SAAVI........ S19SUX) 11AMLIN ......... S99.00 TOCOM _. J319.O0 SCIENTIFIC- EAGLE J119.00 ATLANTA S 119.00 COPY GUARD $59.95 OAK M35B... SW.OO STARGATE 2000... 188,00 ZENITH 1175.00 M.D. Electronics will match or beat any advertised wholesale or retail price. Your best buys and warranties for table converters and d esc ramblers start with a FREE catalog from VI D EXCELLERATOR CABLE CONVERTERS WHEN QUALITY COUNTS For Information Call 402-554-0417 To order or request a free catalog 1-800-624-1150 New Dynatrack™ fine tuning provides unmatched picture quality 550 MHz inner provides 83 channel capacity Sleep timer for Automatic shut off within 1 5-90 minutes 213 switthabl* IIRC / IRC / Standard Switchable 2 Year warranty, Last channel recall. Favorite channel select, Scan Double vented high efficiency transformer far coot performance Stargate-2001 $99.00 Siargate-550XL SI 19.00 With Volume Control Don't settle for anything less. Oj- xC> Om*h*t NEOOIl4 ATJ^s:x>COMJ^YWOtALL5rrV77i^^ *(&■• j* g&fbT OWNHBJHFOF CAHJ TV EQUITHGT. EF TOU AM UNSURE OF TH1SK LAWS B c.o.n. CHECK wmt VOL"* LOCAL OfFK'rAU CIRCLE 53 ON FREE INFORMATION CARD RADIO tubes. Scarce new. used. Extensive listings. Capacitors, etc. Illustrated flyer $1.00 (deductable). DIERS, 4276-E7 North 50th Street, Milwaukee, Wl 53216-1313. CABLE TV descramblers wholesale DRX — 3 DIC with remote $60.00 each for 20 pieces. CHICAGO CABLE VIDEO, 923 South Main Street, Algonquin. IL 60102. 1 (800) 442-9653. No Illinois orders. CODE SCANNER Compact unit copies Morse, RTTY, ASCII codes from your radio on 32 character LCD display. Ten day money back. Model CSCAN $1S9,0O+S5 S&H MICROCRAFT P.O. Box 513R Thiensville, Wl 53092 Telephone (414) 241-8144 REMOTE CONTROL. KEXCHAIN ... Complete w/mini-tfansmiUBf . • and +5 vdc RF receiver ■'■: Fully aaoembfed including plans . .to build your own auto alarm.:. : ::;:. QuanOly die counts a. vatlable : !;: rt%A« rtr Check;vis*or MfC:o <>ii4.y0 Add $ 3 shipping VISITECT INC. BOX 5442, SO.SAN FPAN.^ CA. 34GM i;-(41 5) 872-0128 :- V: Fax (415) 872-2635 PCB and schemata CAD software. Easy multilayer rubberband zoom pan and more. CGA EGA IBM compatibles, S195.00. NUMBER ONE SYSTEMS. 10565 Bluebird Street, Coon Rapids, MN 55433. Demo Disc. (612) 757-8584. SURVEILLANCE — Audio/video.'infra-red.'laser equipment. Industrial or private. 500 ilem catalog $7.00. SECURITY SYSTEMS, 3017G Hudson, New Orleans, LA 70131. PLANS AND KITS y z O CC F- O ID g o < CATALOG: hobby/broadcasting/HAM.CB: Cable TV, transmitters, amplifiers, surveillance devices, computers, more! PANAXIS, Box 130-F5, Para- dise, CA 95967. DAZER ll personal protection device! Plans $8.00. Lasers! Transmitters! Detectors! More! Kits or as- sembled! Catalog $2.00. QUANTUM RESEARCH, 16645-113 Avenue, Edmonton, Alberta T5M 2X2. DESCRAMBLING, new secret manual. Build your own descramblers for cable and subscription TV. Instructions, schematics for SSAVI, gated sync, sinewave. (HBO, Cinemax, Showtime, UHF, adult) $12.95, $2.00 postage. CABLETRONICS, Box 30502, Bethesda, MD 20824. HOW TO use surface mount techniques. Build ultra miniature projects. Included free, two sets plans. Infra red remote control, and light display. Send $15.00 to CHARLIE'S VIDEO, Depl. SMT, PO Box 7782, LaSierra, CA 92503. DIGITAL V.O.M./D.RM. SALES— SERVICE— PARTS FLUKE-BECKMAN-SIMPSON-ETC. U S. MADE ONLY. QUOTATION PRIOR TO WORK. FAST SERVICE, 90 DAY WARRANTY. STANDARDS TRACEABLE TO NBS. SINCE 1948. CALIBRATION CERTIFICATE AVAILABLE. INDUSTRIAL INSTRUMENT WKS. INC. 5745 SALMEN , HARAHAN , LA 70 1 13 504,733-8355 CONTROL timing plans: 3 designs for programma- ble control of relays, power supplies, and more. $8,95 Free info. RON DAY, 1625 Kirkwood Dr., Garland, TX 75041. ROBOTICS! Engines! Inventions! Muscle wires contract with surprising strength when powered. Send business SASE for latest flyer. MONDO-TRO- NICS Co RE, 2476 Verna Ct„ San Leandro, CA 94577. HYPNOTIZE or Relax electronically! Alpha/medita- tion goggles. Complete kit $53.00. Free information MARK WORLEY, Box 261113, San Diego, CA 92196. SURVEILLANCE transmitter kits! Four models of each; telephone, room, combination telephone/ room transmitters tune from 65 to 305 MHz. Catalog with Popular Communications and Popular Electronics book reviews of "Electronic Eaves- dropping Equipment Design," $2.00. SHEFFIELD ELECTRONICS, 7223 Stony Island Ave.. Chicago, IL 60649-2806. POWERFUL single-chip FM voice transmitter, size of a postage stamp, transmits to any FM radio up to one mile away. Complete kit S13.95 postpaid. HERTZ MICRODEVICES, Box 41771-B, LA. CA 90041-41771. SURVEILLANCE electronics, plans, kits, as- sembled. Calalog $4.00. S & S ELECTRONICS, PO Box 36505-1 23E, SanJose, CA 95158. AUDIO! Plans/products — inexpensive, profession- al, amps, mixers, more! Literature/cassette — $3.00! DAVISOUND, Box 521, Newberry. SC 29108. CABLE DESCRAMBLERS OAK M35B COMBO $39.35 Jerrold, Zenith, Hamlin, Sci. Atlanta, Pioneer & MORE! OUR PRICES ARE BELOW WHOLESALE! CABLE-H PLUS 14417 Chase St. #481-A Panorama City, CA 91402 1-800-822-9955 • Other Info. 1-818-785-4500 NO CALIF. SALES - DEALERS WANTED SATELLITE TV FREE catalog — Lowest prices worldwide, save 40 — 60%. Systems, upgrades, parts, ail major brands factory fresh and warrantied. SKYVIStON, 2009 Coltegeway, Fergus Falls, MN 56537. 1 (800) 334-6455. __ VIDEOCYPHER II descrambttng manual. Sche- matics, video and audio. Explains DES, Eprom, Clonemaster, 3Musketeer, Pay-per-view (HBO, Cin- emax, Showtime, adult, etc.) $16. 95, $2.00 postage. Schematics for Videocypher Plus. $20.00. Sche- matics for Videocypher 032, $15.00. Collection of software to copy and alter Eprom codes, $25,00. CABLETRONICS, Box 30502R, Bethesda, MD 20824. FREE CATALOGS 1-800-648-7938 JERROLD HAMLIN OAK ETC CABLE TV Special Dealer Prices! • Compare our Low Retail Prices! • Guaranteed Prices & Warranties! • Orders Shipped Immediately! REPUBLIC CABLE PRODUCTS. INC. 40B0 Paradise Rd. #15. DeptRE591 ICTT Las Vegas, NV 89109 d For all other information (702) 362-9026 V1DEOCIPHER II manuals. Volume 1 — Hardware, Volume 2 — Software — either $34.95, Volume 3 — Projects/Software, Volume 5 — Documentation or Volume 6 — Experimentation $44.95 each. Vol- u me 4 — Repa i r $99. 95 . Volume 7 — 032/H acking S54.95 Cable Hacker's Bible — $34.95. Clone Hacker's Bible — $34.95. Calalog — $3.00. CODs (602) 782-2316 TELECODE, PO Box 6426-RE, Yuma, AZ 85366-6426. BUY BONDS ELECTRONIC ASSEMBLY BUSINESS Start home spare time Investment knowledge or experience unnecessary. BIG DEMAND assem- bling electronic devices. Sales handled by profes- sionals. Unusual business opportunity. FREE: Complete illustrated literature BARTA RE -00 Bui 248 Walnut Creek. Calif. 94597 BUSINESS OPPORTUNITIES MAKE $50/ hr working evenings or weekends in your own electronics business. Send for free facts. MJME INDUSTRY, Box 531, Bronx, NY 10461-0208. YOUR own radio station! AM. FM, TV, cable. Li- censed/unlicensed. BROADCASTING, Box 130- F5, Paradise, CA 95967. LET the government finance your small business Grants/loans to $500,000. Free recorded message: (707) 449-8600. (KS1). IMPOSSIBLE CABLE SYSTEMS! Zenith PZ ♦ Pioneer Cube ♦ Starcom 88 7 ♦ Standard Units ♦ New Generation of TRII ♦ Quantity prices start ■ ^ulji oaf v .:■;,! m.,im. i f TRIMODES & SB'S. i* $25 each Dealers only Call 1-800-933-2242 SSgital ^Equipment Company ef&nerica MAKE $75,000 to $250,000 yearly or more fixing IBM color monitors (and most brands). No invest- ment. Start doing it from your home. (A telephone required.) Information, USA, Canada $1.00 cash. US funds. Other countries $8.00 RANDALL DIS- PLAY, Box 2168-R, Van Nuys, CA 91404 USA. EASY work! Excellent pay! Assemble products at home. Call for information (504) 641-8003 Ext. 5192. MAKE $SS! Become an American electronics deal- er! Profit opportunities since 1965. Call SCOTT PRUETT, 1 (800) 872-1373. WANTED INVENTIONS/ new products/ideas wanted: call TLCI lor free information 1 (800) 468-7200 24 hours/ day - USA/Canada. INVENTORS: We submit ideas to industry. Find out what we can do for you. t (800) 288-IDEA. NEED help with your electronic project, PCB as- sembly/artwork? Write to T.S., PO Box 5275, Flint, Ml 48505. TUBES - 2000 TYPES DISCOUNT PRICES! Early, hard-lo-find, and modem tubes. Also transformers, capacitors and parts for tube equipment. Send $2.00 for 28 page wholesale catalog. ANTIQUE ELECTRONIC SUPPLY 6621 S. Maple Ave. ■ Tempe, AZ 85283- 602/820-5411 SUPER SALE MhM WotM ""v 73...* 79 M..-MS 73...M19 w...*229 77 . . . »149 87 . . . *269 A. new Model 45 . . . *579 ▼ ■■£ KEL VIN. Elaarcntos 5_2 7 Pwrchild Av«„ Plainvim. NY 11803 aB, (516) 349-7SM 1(600) 645-8218 DISTINCTIVE RING SWITCH Add additional phone numbers to a single line with the new Distinctive Ringing service from the phone company. RingDi rector detects ring patterns and routescallstophones.a nsweri ngmachines, FAX 's or modems. 2-port $89. 4-port $149, SIH $5. 1-800-677-7969 FAX 516-676-9225 EXCELLENT TECHNOLOGY 69 smith Street, Glen Head, NY11545 INVENTORS! Your first step is important. For free advice, call ADVANCED PATENT SERVICES, Washington, DC, 1 (800) 458-0352. TRAVEL! High income! Radio officers wanted for shipboard employment. Must have FCC second telegraph license. Rae Echols, AMERICAN RADIO ASSOCIATION, 5700 Hammonds Ferry, Linthicum, MD 21090. Be a TV/VCR Repair Specialist Now you can tram at home in spare time far a money- miking career as a TV 'VCR Repair Socialist. No previous experi- ence necessary. No need to quit your ;ob or scliool. Everything is explained in easy-to -understand language with plenty of draw- ings, diagrams and photos. We show you h.ow to troubleshool and repair video-cassette recorders and TV sets, how to handle npuse cal Is a nd shop repa i r s f or al mo 5 1 any make of television o r VCR. Tools are included with your course so you can gel "hands-on" practice as you follow your lessons step by step Send for free facts about the exciting opportunities in TV VCR Repair and find oul how you can start making money in this great career MAIL COUPON TODAY «™ SCHOOL OFTVAfCR REPAIR, Oepi. ADE0415 U—uunI 325 Oak Street, Scan ton. PA 18515 Please send me full informal ion and color brochure an bow I can learn TV'VCR Repair at home in my spare time. I understand there is no obligation and no salesman will visit me Name Address City/State . Ase_ _ Apt. #_ -Zip .Phone | ) | racS MCM ELECTRON 6SD CONGRESS PARK DR. CENTERVILLE. OH 4545B-4072 A PREMIER Company MCM Electronics A Well-Balanced Parts Catalog. If all you want is a huge assortment of high-quality parts and components, we can tip the scales in our favor in a flash. After all, we stock more than 16,000 items, including loads of name brands (3,000 RCA/GE parts alone!) and the largest selection of Japanese semiconductors in the country! But as an MCM customer, you'll enjoy even more— like a friendly, well-trained sales staff, technical assistance when you need it and a GIGANTIC INVENTORY that lets us ship more than 98% of all orders within 24 hours! So, what are you waiting for? Call TOLL-FREE, 1-800-543-4330, NOW to get your FREE, ONE-YEAR SUBSCRIPTION to the MCM Electronics Catalog cs SOURCE NO. RE-70 £ $ 87 CIRCLE 87 ON FREE INFORMATION CARD PERFECT CABLE CONNECTION !! PeHed Cable Conneclson is totally commiiied to cu^omor satisfaction. Our primary concern is to provide you with (he highest qu al iiy converters and de scram biers al the 'owe si cost We employ full lime technicians to insure hassle Iree service and iroublesnocl any situation Call u* loday and lei us prove to you wtiry we are The Parfeci Cable Connection. • 6 monlhs 1 00% parts & labor ■ 24 months warranty available • Full lechntcal support ■ On-line computer system ■ 30 days money back guarantee ' Most orders shipped *ilrwn 2* hours ■ Visa, MC. AMEX ■ 5% ■ Dealers welcome • ao.D JerroW Ftogil HE 83 W R ' Niw" 400 DAX 3 OtC W R 1 S9 ■ ?3 Ch «p*OtV 1 H9 10 S9 ■ Wtrdcas i:m^c S 89 JQ 65 ■ Automate linfl .Lrfwuj 10 79 50 GO ■ Paronral ock 20 69 ^■p^^^^^WVp^H IOC 55 ■ Midt m Jwi 50 6S -S upwsmH ion CALL . F Mrfa mwnory chmrwk J-wrotd 1 125 ZTACS HI All motels Bt^Bml 20 79 Cb.1I lor pr*c4K 50 CALL 100 CALL |j£2 Jerr^ld 400 SA-3S mvs OR* 31 OS W R 1 75 1 M 10 48 10 79 5 « to 43 20 65 10 45 50 39 50 CALL 50 40 100 35 100 CALL WE WILL MEET OB BEAT ANY ADVERTISED PRICE IN THIS MAGAZINE. PERFECT CABLE CONNECTION 702-358-2763 2209 Oddie Blvd., Suite 321 Spark. NV 89431 THJ£ &Pfl£C tWTOVUTED M A Put*, £ JERVtCS A defense against cancer can be cooked up in your kitchen. There Is evidence ihaj tUei and cancer arc related . Follow these modifications in your daily diet 10 reduce chances of gelling cancer: I * Eat more high-fiber foods such as fruits and vegetables and whole-grain cereals, 2. include darie green and deep yellow fruits and vegeta- bles rich in vitamins A and C. 3- Include cabbage, broccoli, brussels sprouts, kohlrabi and cauliflower. 4, Be moderate in consump- tion of salt-cured, smoked, and nitriu*021 CALL TOLL FREE 1-800-338-0531 i v C^*. 12" woofer made in the USA by Eminence. Paper cone and dust cap with treated cloth surround. 80 oz, magrret. 2-1/2" vented voice coil 8 ohm 170W RMS, 235W max. 40-4.5KHZ response. #RD-290-147 CIRCLE 56 ON FREE INFORMATION CARD 5 89 o z o d LU Q D < DC SCIENTIFIC & ELECTRONIC PRODUCTS LASERS AND SCIENTIFIC DEVICES VRL2K 3mwV!s Red Laser Diode System Kil $159.50 LUSIK Lsstr Beam "Sou nc«" Listener Kit S199.5FJ LHC2X Visible Simulated 3 Color Laser KI1 $14.50 LC7 40 Wall Burning Colling Laser Plain SZG.OD RUB4 Hi Powered Poised Drilling Laser Plans ;.„... ..,.$£0.00 LGU4D 1 to : ■ 1 1 1 . .■ HeNe Vis Red Laser Gun Assembled S1S9.00 LLS1 Laser Lite Shnw- 3 Methnds Pljns S20.00 SD5K See in Ibe Dark Kit SZ99 ,80 EML1K Eleclromarjnelic Coil Gun Kit $69.50 MCP1 Hi Velocity Coil Gun Plans S15.00 LEVI Ltvtlilfnrj Deyite Plans S10.DD EM1 Electronic Hypnotism Techniques Plans ; ,,..,..510.00 HIGH VOLTAGE AND PLASMA DISPLAY DEVICES HVM7K 75.000 Veil DC Variable 0ui|)ut Lab Source Kit 5149.50 ICIGoK Ion Roy Gun Kil. project energy withnul wires $69.50 NIG9K I2V/115 VAC Hi Ool Neg Ion Generator Kit 534 51- EMA1K Telesinetic Enhaocer/Electric Man Assembled $99.50 1G5K Lightning Display Globe Xil 554.50 BTC1K Worlds Smallest Tesla Coil Kit $49.50 8TC3K 250KV Table Top Tesla Coil Kit ....$249.50 BTC5 1.5 Million Volts Tesla CdII Plans $£0.OD Ji. 3 Jacobs Ladder -3 Models Plans $15.00 GRA1 Anti Gravily Generator Plans $1 0.00 PFS20 Plasma Fire Saber Assembled $09.50 D PL. :'■ Dancing P I as m a lo Music a nd Sou nils Assembled $79.50 SECURITY AND PROTECTION DEVICES ITM10 100,900 Voll Inlimidalor up lo 20' Assembled $129.50 IPG70 Invisible Pain Field Blast Wave Gen Assembled $74 50 PSP4K Pbasor Sonic Blast Wave Pistol Kit $59.50 LISTI0 Inlinlly Xmtr. Listen in Via Phone Assembled $199.50 TAT3D Automatic Tel Recording Device Assembled $24.50 VWPH7K 3 Mi. FM Auto Tel Transmiller Kit $49.50 FMK1K 3 Mi FM Voice Transmiller Kit $39.50 HD01K Homing/Tracking Beeper Transmitter Kit, $49.50 EASY OFtDCBING PROCEDURE TOLL FREE 1.SCD-22M 7D5 or 24 HUE OH 1 -603- 573 -4730 or FAX IT TO 1-E03-572-540S VISA. MC, CHECK. MO III US FUNDS INCLUDE 10-.i SHIPPING DROEflS S100.UO4 UP ONLY ADD S10.00. CATALOG 51.00 OR FREE WITH OP DEO. INFORMATION UNLIMITED P.O. BOX 716, DEPT. R3, AMHERST, NH 03031 CABLE TV DESCRAMBLERS Qty 1 10 20 Jerrold (Type) SB-3 89.00 56.00 43.00 Jerrold (Type) FTB-3 99.00 69.00 54.00 Scientific Atlanta SA-3 99.00 69.00 54.00 Hamlin MLD-1200 99.00 50.00 45.00 OakN-12 99.00 59.00 58.00 Tocom 5501 169.00 139.00 125.00 Eagle PD-3 119.00 64.00 60.00 COMBINATION UNITS Jerrold (Type) DRX-3DIC 169,00 109.00 89.00 Jerrold (Type) Starcom 6 279.00 239.00 209.00 Scientific Atlanta 8535 229.00 209.00 199,00 Scientific Atlanta 8580 299.00 269.00 259.00 Oak M35B 99.00 59.00 49.00 OTHER TYPES ARE OFTEN AVAILABLE * We specialize in large quantity discount * Call us for pricing on 50 and 100 lot * We will not be undersold on large quantities * Please have the make and model number of the model you need when calling for information K.D. VIDEO P.O. Box 29538, Mpls. MN 55429 TOLL FREE 1-800-327-3407 NEXT MONTH IN Po pular Electronics Exciting Features, Projects, Reports, & Columns • A NEW DECADE IN • BUILD THE PROTOMAX CONSUMER ELECTRONICS PROTOTYPING STATION Circuit design is a snap when every- thing is at your fingertips There's plenty of high-tech excite- ment in store for the 1990s • EXPERIMENTS IN ELECTROCHEMISTRY Fascinate yourself and your friends with these fun experiments • BUILD THE ACCESS III A telephone-operated, remote-con- trol power switch for your computer Po pular Electronics And there is more! PRODUCT REVIEWS— Sony Au- dio/Video Switcher, Nakamichi CD Player2 CD Changer, Memorex Headphones, and more DX LISTENING— Tune in to Radio Bangladesh COMPUTER BITS— What good is Hypertext? 1INK TANK — A primer on cur- rent-limiting resistors, a telephone in- tercom system, a Christmas-tree light tester, and more HAM RADIO — Some simple fixes for annoying problems ANTIQUE RADIO— America's love affair with the Theremin PICK UP lu piUdi IlCUlUlllta AT YOUR FAVORITE NEWSSTAND, CONVENIENCE STORE, OR SUPERMARKET. 90 * * * * PRESENTING * * * * CABLE TV DESCRAMBLERS ***** STARRING ***** JERROLD, HAMLIN, OAK AND OTHER FAMOUS MANUFACTURERS - FINEST WARRANTY PROGRAM AVAILABLE • LOWEST RETAIL (WHOLESALE PRICES IN US • ORDERS SHIPPED FROM STOCK WITHIN 24 HRS • ALL MAJOR CREDIT CARDS ACCEPTED FOR FRIE CATAIOG ONLY I-80O-345-8927 . FOB ALL INFORMATION 1-018-709-993^/ PACIFIC CABLE CO.. INC. 7325 r /j Reseda Blvd.. Dept.2102 Reseda. CA 91335 PAT TV AND SATELLITE DE SCRAMBLING ALL NEW 1991 EDITION Olk nasi yet Tfte very laEcsl in desyimWing preurts , fr/pasas, lurn-em for cable, wireless and satellite Only SU.M Oihe r -av T^' editions, '-'-z T (Ba&cs of AB Systems) SI 4.95 1 939 f (Sffiw SI 4 35 Bwld saldm* Systems under $600 SI 2.95. Wireless Cable ttar.dbgrtS9.95 Any iABSplasliccase)AA SM-46 1 ' .- Hi -free so r. G P M A A A SM48A 4'-,. Hi. Precision D.P M iw'ABSclaslic caseOAAA SM-43 3^ Mulh-Funchoral LCD D M p (vvllo'd Func1ion|AA SM10O 1 SOMC DigrlaL f reguency Counter A A A ^C-IOOOA 1 GHz Frequency Counler * . . 334 50 343 00 38.00- 43.00 41 20 52 00 3600 44 50 79 00 90 00 17300 MODEL 001 00? 003 004 0O5 006 DESCRIPTION 23V I 2 CA 10 30V 1 2 6A 36V i 2 3A 40VI26A 24VJ2 6A 26V X 2 3A MATCHING PRICE TA-800 MK2. TA-802. TA-8J0A. TA-I000A. TA-1500 . S 27.00 TB-503. TA-323A TA-400, TA-300. TA-377A . ... 22 00 FA-177 .28.00 TA-120MK2 „_ 22.00 TR-355B 16.00 TR-355A IS 50 5 .'.■ ,..■:- i .'■■■;- ..-,■..!■ man , ■■■ -i. ■ ChKftta IC.OI3 kshn EiOJJ.lwtata '.' i ■■■■■!■ ■ j. -.■..■ ;■:.,..'-;:■ •: •>,. n-, . -.1 ;,:..;■■ , Gu'Mi !•>':■:. ?. Sho-.vroorii Iioj"'. iP.;iuin: rbne outKMUS 1*aaA*c&outiatooacMfr>ir*'tarQrf5mri r nviF2*i* <*tott<&\ariten . * aii ika^nifi!^ uno 'tiiw 1 30 di^ w *Ans4tns Mon Ihtu Fn. 9:30 am lo 5:00 prh at ca pwrno «dd m**» lu 9 .75"*. ' Ail mrchar> Qr» tf -etfu ire sutfrea topic* «Je Prce* -vo sijduici tocna^*it»^ip» 1 c'«^cw W#w*rw Sat. HO 00 am lo 5.00 pm MARK V ELECTRONICS, INC. - 8019 E. Slauson Ave, Montebello, CA 90640 ^H^] CIRCLE 93 ON FREE INFORMATION CARD UJ I O Q < Eli 'Radio REPRINT BOOKSTORE □ 221 Popular Electronics (1991 back Issues) $4.00 Write in issues desired D 220 Popular Electronics (1990 back issues) $4.50 Write in issues desired □ 119 Popular Electronics (1989 back issues) $4.75 Write in issues desired □ 118 Hands-On Electronics (1988 back issues) $5.0(1 Write in issues desired □ 117 Hands-On Electronics (1987 back issues) $5.25 Write in issues desired O 116 Hands-On Electronics (1986 back issues) $5.50 Write in issues desired □ EH91 Experimenters Handbook (1991) . . . .$4.50 □ EH90 Experimenters Handbook (1990).,.. $5.00 □ EH88 Experimenters Handbook (1988-89) $5.50 □ EH87 Experimenters Handbook (1987) . . . $6.00 D HH91 Popular Electronics Hobbyist Handbook (1991) $5.00 □ HH90 Popular Electronics Hobbyist Handbook (1990) $5.50 □ HH89 Popular Electronics Hobbyist Handbook (1939) $6.00 D 126 Radio-Electronics Annual 1986 $6.00 □ 211 Radio-Electronics (1991 back issues) $4.00 Write in issues desired P 210 Radio-Electronics (1990 back issues) W.5Q Write in issues desired D 109 Radio-Electronics (1989 back issues) .$4.75 Write in issues desired D 108 Radio-Electronics (1988 back issues) .$5.00 Write in issues desired □ 107 Radio-Electronics (1987 back issues) $5.25 Write in issues desired n IBS Radio-Electronics (1986 back issues) $5.50 Write in issues desired REPRINTS REPRINTS I I 169 TiiinkTank (133 Circuits) $3.50 □ 169A Think Tank Vol. 2 S3.BD □ 168 Fact Cards (#34-66) S4J0 □ 168C Fact Cards (#67-99) $3.50 a 168D Fact Cards (#100-132) $3.50 D 167 Designing With IC's $4.00 ["J 166 Collected Works ot Mohammed Ullyses Fips (62 pages, April Fools Collection) .... $5. DO □ 165 How to Repair CD Disc Players $5.00 □ 164 Modern Electrics [April 1908) $3.00 □ 163 Receiving Satellite TV $5.00 D 162 Build Your Own Satellite TV Receiver $5.00 D 161 Descrambling (Feb. 1984) $3.00 CI 160 New Ideas - 42 Circuits $3.50 n 159 Low Frequency Receiving Techniques Building and using VLF Antennas S5.00 □ 15B Electro Importing Co. Catalog (Circa 1918) $5.95 □ 157 All About Kits $2.00 □ 156 How To Make PC Boards $2.00 □ 155 IBM Typewriter To Computer $2,00 □ 154 How To Repair VCR's S3.S0 □ 150 Pay TV Decoder (1981) $3.00 To order any of the items indicated above, check off the ones you want. Complete the order form below, include your payment, check or money order (DO NOT SEND CASH), and mail to Rarlio-Eleclrortics, Reprint Depart- ment, PC. Box 4079. Farmingdale, NY 11735. Please allow 4-6 weeks for delivery. If you need a copy of an article that Is In an issue we indicate is unavailable you can order it directly from us. We charge 50$ per page. Indicate the Issue (month & year), pages and article desired. Include payment in lull, plus shipping and handling charge, Make checks payable to Gernsback Publications. Inc. ARTICLE PAGES MONTH YEAR TOTAL PAGES (a 50 C each TOTAL PRICE MAIL TO: Radio-Electronics Reprint Bookstore. PO. Box 4079, Farmingdale NY 1 1735 SHIPPING CHARGES IN USA & CANADA 50.01 to $5.00.. $1.25 $30.01 to 40.00 ... $5.01 to $10.00 $2.00 $40.01 to 50.00 . , . $10.01 to 20. 00 S3.00 S50.01 and above.. $20.01 10 30.00 S4.00 S500 S6.00 S7.50 All payments must be in U.S. lends SORRY - We only ship to USA 8 Canada Total price of merchandise $ . Sales Tax (New York Slate Residents only) $ . Shipping Charge (see chart) $ . Name Address . Total Enclosed. City. .State . .Zip. RE591 PCN continued from page 74 for the most part favoring the set- aside of spectrum for PCN's (providing it comes from some- one else's allocation). It will take at least three to four years (and that's optimistic) until the dust settles and permanent alloca- tions to PCN's are made. If the tests show that spread spectrum is indeed a feasible way of intro- ducing PCN's without treading on the toes of the current spec- trum users, the FCC's problem will be largely solved. Otherwise, it will have to clear spread spec- trum by ordering occupants to move to a higher band. After that, the FCC then has to consider the rather large— and perhaps over- whelming — problem of how to li- cense PCN's. One possibility of licensing PCN's is the cellular paradigm. The FCC divided the country up into over 700 markets, urban and rural, and allotted two licen- sees to each, one for the tele- phone company in the area, and one awarded by lottery. While the process led to a lot of people get- ting extremely rich, especially those involved in preparing ap- plications for licenses, results were less than satisfactory, since two cellular companies have not provided adequate competition (cellular usage prices have not fallen since services were inaugu- rated in the mid-80's). Another possibility is to have two to four national licensees or, alter- natively, licenses could be granted on a regional basis with two or three licensees in each re- gion. If the FCC chooses that ap- proach, there will be a feverish scramble for whatever licenses are offered and there will cer- tainly be several sore losers. The upshot of all this is that many of Americas largest compa- nies will be scurrying frantically in the next few years to ensure that when the dawn arrives, they will have secured their share. The ultimate beneficiary will be the communications user, who will have a new-found freedom to go anywhere without sacrificing the ability to keep in touch with any- body at any time. R-E 92 We Have QUALITY PARTS • We Have DISCOUNT PRICES > We SHIP FAST m 5 ma -84 HPM slon goat maor. )ned for 24 VdC. aw on 12-24 Vdc. 30:1 gear reduction . 2.07 long X 1.18" square mounting brack- 6 mounting holes on 0.97" centers. Motor lood torque whan used at 24 Vac. CAT*MOTG-15 $12.00 each I.E.C. POWER CORD 12 Vdc POWER PACK FLOURESCENT FIXTURE 6 foot BLACK, SPH-386 jack to 3 prong molded A. C. plug. Fits most computers, computer terminals and test equipment. CAT#LCAC-C6 $3.00 each 12 Vdc 1 Amp. power pack, 8 ft, 2 conductor pwoer cord on input. 22* cord with stripped and tinned pigtail leads on output. 3.2" X 2.3" X 1.9". CAT#DCTX-121 $5.75 each Fixture for single mini bi-pin 6", 4 wall lluores- cent lamp. Starter switch, sockets and ballast are mounted on 7 1/4" X 3 1 /4" malar plate. Includes 8 toot power cord with slrain relief. Use with standard fluorescent lamp for display Fighting or with ultraviolet lamp lor special at leas or EPROM erasure. u.L. listed. CAT*FLX-1 $3.00 each SWITCHES Dtp P.C. Pushbutton Schadow Digriasi mSE D.T. momentary iburton. Mounts in in DIP conliguration. gned for low current switching appli- ms. Grey keycap Is 0.68" X 0.67", CAT4PB-2S f 1.00 each 10 lor $9.50 ■ 100 for $85.00 rcury Tilt Switch diameter 65' long =€D jury tin switch, S.P.S.T.Croses circuit n switch Is tilted approx. 5 degrees. CAT#MS-3 $1.00 each 10 lor $9.50 • 100 for $85.00 tary BCD Switch f—± »# 2310-026 \%1 ) 10 position ^f-W try swkch. DIP configuration fits in idard 8 pin I.C. socket. Right angle 3. Screwdriver actuation. 0.42* cube. CAT#RDIP-2 }l. 75 each 10 for $16.00- 100 for $145.00 Miniature Toggles Rated: 3 amps @ 120 Vac .D.T. (ON-ON) P.C. mount t#MTS4PC $1.00 each / or $9.00 - 1 00 for $60.00 J> ! O. T. (ON-ON) solde r lug s £*. '*MTS-4 $1.35 each Cl or $12.50 -100 for $110.00 ^r '.D.T, (ON-QH) solder lugs T#MTS-8$1.75ea. 1 f or $ 1 S.OO '.D.T. (ON-ON) P.C. mount T#MTS-SPC $2,00 ea, 10 lor $17,50 LEPHONE KEYPAD Sutton telephone pad. Ivory finish. 3" x 2,2" x 0.58- thick. Irix encoded. al for telephone or writy keypad. T#KPT-l$1.00each -I0for$9.00 OPTO-SENSOR W/Oplron - OPB5447-2 rtmilter/sensor pair in , j " T fc aang ular package wfth f([ 3?£"B color coded leads. TiOSR-4 2 for $1.00 ~J PH0T0FLASH CAPACITOR Rubicon CE 210 Mid 330 Volt photoflash capacitor. 0.79" oTa. X 1.1" high. These are new capacitors that have been propped with 1.4" black and red wire leads soldered lo Ihe terminals. CAT* PPC-210 $1.25 each -10 for S1 1.00 100 for $100.00 Large quantities available. Call for pricing. RECHARGEABLE BATTERIES 6 Volt 1 Amp/Hour Japan Storage B artery Co. Portalac w=f»s^? #PE6V1 VS-J^ 6 Volt 1 Ah h Y^ rechargeable J sealed lead-add v ~~~^^ (gel celt 2" X 1 .635" X 2" ht. Batteries are propped with 5' black and red leads terminat- ed wilh 2 pin connector, CAT4GC-61 $4.75 each 10 for $42.50 Nickel-Cad AAA SIZE $1.50 each 1.2 veils 1 BO mAh CAT* NCB-AAA AASIZE $2.00 each 1 .25 volts 500 mAh CAT* NCB-AA AA SIZE $2.20 each WITH SOLDER TABS CAT* NCB-SAA C SIZE $4.25 each 1.2 vote 1 200 mAh CAT* rMC B-C DSIZE $4.50 each 1 .2 vote 1200 mAh CAT* NCB-D HALL EFFECT SENSOR i P.C. RELAYS Microswrtch *SS41 Tiny, solid state switch reacts Instantly to proximity of magnetic field. Operates at extremely high speeds, up to 100 khj. Case siie: 0.12" X 0.17" X0.06" thick. 4.5 Vdc to 24 Vdc supply voltage. 10 ma sink type digital output. Operating gauss - 1 5 to 40. P.C. leads. CAT* HESW-3 $1.00 each • 10 lor $9.00 1 00 for $65,00 ■ 1000 for $750.00 INSTRUMENT ENCLOSURES High quality molded ASS Instrument enclosures. Integrated PC board standoffs and two eets of vertical mounting skits for front and rear sub panels. All enclosures are 6" wide X 6 1/4" deep. Choice of three his. includes non-skid rubber leel and hardware. Available In beige. Ivory, black, and blue. F-an*jftL CAT* 21/4' CATJTMB-A I7.50«ach lOtateSOO 2 J*fi* CAT* M B- B 17 75 * adl 1 lor S67 50 y CAT* M B-C Sfl CO (-m 1 br 170 00 Plu&a specify color. RG-11/U VIDEO CABLE 100 ft. or 200 ft. rolls ol RG 1 t/U 75 ohm cable terminated to heavy duty F connectors. Includes 75 ohm terminator and ■« * ■■ > i F-S1 splicer on one end. New cables manufactured for IBM PC networks. IBM PIN 1 501908 COMrSCOPE. CAT* RG-tt-l 100 ft. roll $15,00 CAT* RG-1 1-2 200 It. roll $27,50 FLASH ASSEMBLY New compact flash assembylroma U.S. manufacturer of cameras. Operates on 3 Vdc and measures GEXOXEJ' 21/2"x11/4", IdeaJ for use as a slrobe, warning light or attention getter. Includes hook-up diagram. CAT* FSH-1 $3.75 each 10 lor $35.00 - 100 lor $325.00 The following relays all have p.c. pins lor both Input and output as well as quick-connect terminals ontheoutput. 1.5"X 1.05" X1.08-, UL&CSA listed. IZVdcSPDT Potter & Brumfiefd * T91R5D22- 12-02 12 Vdc 155 ohm coil. Normally open contacts rat- ed 20 amps, Normally closed contacts raied 10 amps. CAT#RLY-31 $2.50 each 10 lor $22.50 12 Vdc, SPST N. O. Potter & Brumfleld # T91R5D22-12-01 12 V 16LP,.., 24LP 28LP 40LP Wire Wrap (Gold) Level #2 8WW $.49 14WW 65 16WW ...69 24WW 1.05 28WW... 1.29 40WW 1.79 Soldenail Standard & Header Plug Sockets Also Available .$.11 ...12 ...13 ... .19 ... .22 ... .28 24 Hours A Day! J AMECO 24 Hour Order Hotline (415)592-8097 FAX: (415) 592-2503 {415)595-2664 1355 Shore way Road Belmont, CA 94002 Look to Jameco • Wide selection of integrated circuits and components • Quality prototype and test equipment • Computer kits and accessories Additional items that Jameco offers; • Tools • Cables ■ Connectors • Data Boohs • Motherboards • Memory ■ Math Coprocessors • Computer Accessories ■ Power Protection Equipment • Much, much more ! Let us show you what we have to offer; call or write for the latest Jameco catalog! $50.00 Minimum Order Data Sheets • 50e each For a FREE 90-Page catalog send $2,00 to cover first Class Postage and Handling © 1991 Jameco Electronics 5/91 CA Residents Add 6.00%, 6,50% or 7 00% Sales Tax Snipping, handling and insurance are additional- ( Costs may vary according to wmghl and shipping method) Terms: Prices subject to change without notice. Items subject to availability and prior sale. Comptolo hst ot lefmsvw*ctant«s ht avajlawc upon r&quesl, IBM H a regitbflcad 1rad«iurk ol Insnf rjionnl Bunnasa UAChnH visa MMC Please refer to Mall Key 2 when ordering Customer Service 'Technical Assistance • Credit Department • All Other Inquiries • {41 5) 592-8097 • 7AM - 4PM P.S.T. CIRCLE 114 ON FREE INFORMATION CARD £ 5 95 c/j o z O £C \- O W -^ UJ Q < rr 96 SAVE MONEY. DON'T RENT! CABLE TV DESCRAMBLERS, CONVERTERS, & ACCESSORIES. Save hundreds of dollars owning instead of renting from the cable company Easy to order and install. Name brands- Pioneer, Oak, Panasonic, Jerrold, Scientific Atianta and more. We're famous for lowest prices, excellent service and immediate delivery. All products fully warranted. Your satisfaction is 100% guaranteed. CALL FOR FREE FULLY ILLUSTRATED 16-PAGE COLOR CATALOG. (800)234-1006 3 FORI SPECIAL ON SUB-MINIATURE VOICE FM TRANSMITTERS. KITS CONTAIN PC BOARDS -FMX-1 LONG RANGE (3 Ml) ULTRA SENSITIVE FM VOICE XMTR with fine tune, range control plus S34.50 •TELX-1 TELEPHONE FM XMTR (3 Ml) auto- matically operates when phone is used. Crystal clear clarity with fine tune and range control. Non detectable ....S34.50 m ■ATR-1 AUTOMATIC TELEPHONE RECORDING DEVICE tapes telephone conversation all automatically $19.50 ALL THREE OF ABOVE FOH :S69.50 CALL OR SEND VISA, MASTER CHARGE, MONEY ORDER, ETC, TO AMAZING CONCEPTS. BOX 716, AMHERST, NH 03031. (603) 673-4730. ADVERTISING INDEX RADIO-ELECTRONICS does not assume any responsibility for errors that may appear in the index below. Free Information Number Page 108 AMC Sales 16 75 Ace Products 23 107 All Electronics 93 — Amazing Concepts 90,96 84 Appliance Service 23 67 Banner Technical Books 26 98 Beckman Industrial 13 109 C&S Sales CV3 — CIE 3,31 — Cable Ready Company 96 180 Cable Warehouse 24 — Command Productions 13 58 Cook's Institute 16 182 D&D Electronics 73 187 Datak Corporation 24 127 Deco Industries 23 183 Electronic Goldmine 89 — Electronics Book Club 5,81 121 Fluke Manufacturing CV2 176 General Technics .23 192 Global Specialties 17 — Grantham College 15 86,193 Heathkit 27,64 — Hi-Tech Electronics 23 114 Jamcco ..94,95 104 Jan Crystals 16 1 15 Jensen Tools 23 — King Wholesale 85 87 MCM Electronics 87 53 MI) Electronics 86 93 Mark V. Electronics 91 190 Matsushita Service Co 14 61 Microprocessors Unltd 83 117 Mouser 14 — NRI Schools 21 188 Optoelectronics 25 56 Parts Express 89 — Perfect Cable 88 1 89 Peripheral Technology 83 101 Pomona Electronics 7 78 Radio Shack 32 178 181 92 123 191 179 185 186 RE Reprint Bookstore 92 SCO Electronics 71 Sencore CV4 Star Circuits 26 Tech Spray, Inc 26 Tektronix 1 1 Test Probes 73 The SPEC-COM Journal 13 Unicorn 88 U.S. Cable 71 Vicjo Publications 27 WPT Publications 76' Wholesale Cable 91 ADVERTISING SALES OFFICE Gernsback Publications, Inc. 500 B Bi County Blvd. Farmingdale, NY 11735 1 (516) 293-3000 President: Larry Steckler For Advertising ONLY 516293 3000 Fan 1-516-293-3115 Larry Steckler publisher Christina Estrada assistant to the President Arline Fish man advertising director Denise Haven advertising assistant Kelly McQuade credit manager Subscriber Customer Service 1-BO0-288-O652 Order Entry for New Subscribers 1-800-999-7139 7:00 AM - 6:00 PM M-F MST SALES OFFICES EAST/SOUTHEAST Stanley Levitan, Eastern Sales Manager Radio-Electronics 259-23 57th Avenue Little Neck, NY11362 1-718-428-6037. 1-516-293-3000 Fan 1-718-225-8594 MIDWEST/Texas/Arkansas/Okla. Ralph Bergen, Midwest Sales Manager Radio- Electronics 540 Frontage Road — Suite 339 Northfield, IL 60093 1-708-446-1444 Fax 1-708-446-8451 PACIFIC COAST/Mountain States Marvin Green, Pacific Sales Manager Radio- Electronics 5430 Van Nuys Blvd. Suite 316 Van Nuys. CA 91401 1-818-986-2001 Fax 18 18-986-2009 RE Shopper Joe Shere, National Representative P.O. Box 169 Idyll wild, CA 92349 1-714-659-9734 Fax 1-714-659-2469 48ho UR ELENCO & HITACHI PRODUCTS 4S hour shipping AT DISCOUNT PRICES SHiPPING Hitachi RSO Series (Portabla Real-time Digital Storage Oscilloscopes) VC-S023 - 20MHz, 20MS/S S99/mo - 50MHz, 20MS/S $120/mo" 50MHz. 20MS/S $135/mo' SIESfrno' $200/mo" VC-6024 VC-6025 VG-604S VC-6145 LEASING AVAILABLE For all Hitachi Scopat - Call for details ' Based on 24 months except V-l 150, VC-6045, VC- 6145 (36 monliis) 100MHz. 40MSte_ 100MHz, 100MS/s_ RSO's from Hilaehi feature roll mode, averaging, save memory, smoothing, interpolation, pretrigg Bring, cursor measurements. These scopes enable more accurate, simplisr observation of complex waveforms, in addition to such functions as haidcopy via a plotter interface and waveform transfer via lha RS-232C interlace. Enjoy the comlott of analog and I he power (o digital. 20MHz Elenco Oscilloscope $375 M0-12S1 ■ Dual Trace Component Tester • 6' CRT • X-Y Operation • TV Sync • 2 P-1 Probes Hitachi Portable Scopes DC to 50MHz. 2-Channel, DC offcet (unc- tion, Alternate magnifier; function V-525 • CRT Readout. Cursor Meas. _ $1,025 V-523 - Delayed Sweep $995 V-522 - Basic Model _ $895 V-422-40MHz $795 V-223 - 20Mhz delayed sweep $695 V-212 - 20MHz $425 HITACHI COMPACT SERIES SCOPES This series provides many new lunctions such as CRT Readout, Cursor measurements (V- 1085/1 065/665), Fre- quency Ctr (V-1085), Swflflptimo Auto ranging. Delayed sweep and Tripper Loch using a 6-inch CRT. You dont feel the compactness in terms of performance and operation. V-660 V-665 60MHz, Dual Trace_ 60MHz, DT. wrcursor V-1060 - 100MHz, Dual Traca V-1065 - 100MHz. DT, w/cursor V-1085 - 100MHz, QT, w/cursor_ V-1 1 00 A - 1 00MHz, Quad Trace^ V-1150 - 150MHz, Quad Trace _$1.195 $1,345 $1,425 $106Vmo' SUSVmo' _$125/mo' _$115/mo' Elenco 35MHz Dual Trace 50MHz *H33 MO- 1252 • High luminance 6' CRT • 1mV Sensitivity • 6KV Acceleration Voltage • 1 0ns Rise Time • X-Y Operation • 1 Axis • Delayed Triggering Sweep • Includes 2 P-1 Probes All scopes include probes, schematics, operators manual and 3 year (2 yrs for Elenco scopes) world wide warranty on parts a labor. Many accessories available for all Hitachi scopes. Call or write for complete specif cations on these and many other fine oscilloscopes. FREE DMM with purchase of ANY SCOPE SCOPE PROBES P-1 65MHz. lx, lOx $19.95 P-2 100MHz, lx, lOx $23.95 B + K TEST EQUIPMENT All Models Available Call for special price Digital Capacitance Meter CM-1550B $58.95 9 Ranges .1pf-20.OOuuld .5% basic accy. Zero control w/ Case Big 1' Display Digital LCR Meter LC-1801 $125 Measures; Coils 1UH-200H Cap5,1pf-200ul »55e Res .01 -20 W Multimeter with Capacitance ft Transistor Tester $55 CM-1500B Reads Volts, Ohms Current, Capacitors. |,iiil^ Transistors and Diodes t with case Big 1" Display FLUKE MULTIMETERS All Models Available Call for special piice Quad Power Supply XP-580 $59.95 2 -20V @ 2A 12V @1A 5V@3A ■5V § .5A Fully regulated and short circuit protected Triple Power Supply XP-620 Assembled $65 Kit $45 2to15V@1A, -2to-15V@1A (or 4 to 30V @1 A) and F V @ 3A Ail the desired lealures for doing experiments. Features short circuit protection, all supplies AM/FM Transistor Radio Kit with Training Course Model AM' FM 108 $26.95 14 Transistors 4 5 Diodes Makes a great school project True RMS 4 1/2 Digit Multimeter M-7000 $135 .0514 DC Accuracy .1% Resistance with Fraq. Courtier and Deluia Case GF-8016 Function Generator with Freq. Counter $249 Sine. Square. Triangle Pulse, Ramp, .2 lo 2MHz Freq Counter .1 - 10MHz GF-801S without Freq. Meter $179 Function Generator 5 --,:■ ' i Blox "...r~r! $28.95 Provides sine, triangle, square wave Item 1Hz to 1MHz AM or I M capabiEity Learn to Build and Program Computers with this Kit Includes: All Parts, Assembly and Lesson Manual Model mm-booq Wide Band Signal Generators $129.00 Starting from scratch you build a certiorate system . Our V4CTQ Mas ti?r trainer teachas you lo write into RA Ms. ROMs and run a -80S5 micrcpfoceKor, which uses similar machine language as IBM PC. Robotics Kit for above (MM8010) 71.95 WE WILL NOT BE UNDERSOLD! UPS Shipping: 46 States 5% {$3 Mm $10 Max) Shipping IL Res., 7% Tax FAX: 708-520-0085 SG-9000 $129 RF Req 1MK-450Mrte AM Modula- tion of IKHz Variable RF output SG-9500 m/ Digital Display t 150MH; built-in Counter S249 XK-500 DIGITAL / ANALOG TRAINER A complete mlnUlab for building, toiling, prototyping analog and digital circuits EI*nWt Digital ■' Analog TralfUji ;t Spet&'iy ooiignM 1or jCIhhiI propels. -*:ih S BM In pOwflr supplies. Includti a twicSoh nortdrator imjh contlnouilif vaHiWB L tin*, irlsnguuu, iquara *»« tornu. A* powar ■uppikn ara rogu jt»a afldpr0t«(W against Shorn POWER SUPPLIES ■ Vs'otM* Pewiv Svoptf • *1.2Sto90VDCtV -5 Amp {+l.MluiSVDCC 1 A«|3] ♦ -l,Sto-MVPC(f iAmp » .iSVDC^iAmp * -12VDCC 1 Amp • ♦SVDCflHiMnp ■ 3QVAC Canhw ripc*3 tj ISVAC dlAmp ANALOG -SECTION - Firetcn GvvtKt Sin*, TriinguUr. ITlJMrtWHIIIllTIH * Froqijifleir*^*"^ « '« rtngtt Uom 1 10 1Q0KH7 DIGITAL - SECTION » Twq no bpunc* *>yt MHtH - E-ght LEOrudoLtis TTL &jflr»wJ - Cbcfc \iKU9tHrt 1 la lM^III ■ Ckso. atT¥rlj1uct4 SVPP kjuJ.-c wi-n BREADBOARDS * 2 FJnadtxunti. hcTi ccniti twO 14 porti (total 1 ,WD r C & S SALES INC. 1245 Rosewood. Deerfield, IL 60015 l«IMH2«-7711 f 70S I 541-0710 15 Day Money Back Guarantee 2 Year Warranty fv .cm subject to change WRITE FOR FREE CATALOG CIRCLE 109 ON FREE INFORMATION CARD Introducing a new companion to your VA62A Universal Video Analyzing System! Isolate All Playback Or Record Problems In All VCRs . . . Now And In The Future, Or Your Money Back! VA62A Universal Video Analyzer VC93 All Format VCR Analyzer '— - Patent Pending Now you'll have everything to completely analyze all VCR video, audio, and servo problems. Automatic Servo Analyzing: (patent pending) Automatically determine if the VCR has a capstan servo, cylinder servo, luminance/chrominance circuit defect in virtually the time it takes to connect to the video and audio line outputs.* Exclusive Video Head Substitution: Never again install another video head without being 100% positive it will fix the problem. Exclusive video head substitution signals isolate head problems from all other circuit problems. Exclusive Hi-Fi Stereo And Audio Signals: Finally there is an answer for troubleshooting VCR Hi-Fi audio circuits. Isolate defects from the spinning heads to the line outputs. Isolate Defects Throughout The Entire VCR: Exclusive phase- and chroma-locked drive signals isolate problems in any stage from the heads to the output. Every signal you need is there, including: FM luminance, chroma, video, and head switching (SW30) signals. Includes Extra Features To Complete Your Servicing Needs: You get: an Internal NTSC video pattern, standard video and audio line output, a servo sub bias supply to 10 VDC, an autoranged DC and PPV meter, plus it supports all common VCR formats, * Using the optional Servo Performance Test Leads and Servo Performance Test Tape. Call 1-800-SENGORE ext. 544 for more information! (736.2673) CIRCLE 181 OK FREE INFORMATION CARD