The how-to magazine of electronics AN INTERTEC PUBLICATION ...americanradiohistory.com/Archive-PF-Reporter/80s/EST-1987-12.pdf · The how-to magazine of electronics... AN INTERTEC

The how-to magazine of electronics... AN INTERTEC PUBLICATION

E EOTROAOServicing &Technology DECEMBER 1987/$2.25

Troubleshooting the chopper circuit Computer -aided circuit design

Tracking down remote control problems.

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More Functions. Smaller Budget.Beckman Industrial Circuitmate" DMMs

put hFE, Logic, Capacitance, Frequency andTrue RMS In Your Hand. For Less.

Get more, for less. It's a simple defi-nition of value. For DMMs, value meansfinding the combination of capabilities thatmeets your needs at the right price. Withoutlosing sight of accuracy and reliability.If you want more functions at a low price,Beckman Industrial's Circuitmate' DigitalMultimeters are the best value around.

From the pocket -sized DM2OL to theDM85O, with true RMS capability and accu-racy to 0.05 % ± 1 digit, Circuitmate DMMsgive you the functions you need.

For instance, the DM2OL puts both aLogic Probe, a transistor gain function (hFE),and a full range of DMM functions in thepalm of your hand. For only $79.95.

Then there's the DM25L. Where elsedoes $99.95 buy you a Logic Probe, capaci-tance measurement, transistor gain function(hFE), and 24 DMM ranges including resist-ance to 2000 megohms? Nowhere else

When high accuracy counts, there's theDM8OO with a 41/2 digit display. The DM8OO

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DM20L Pocket -Sizew/Logic $79.95*TTL Logic Probe: 20MHz

Hilo/off indicationsDetects 25nS pulsewidths

hFE (NPN or PNP):1 range (1000)

DMM: Input Impedance -10 MegohmsDCA/ACA-5 ranges(200µA to 2A)

Ohms -8 ranges (200 ohmsto 2000 Megohms)

Continuity beeper

also gives you frequency counting A full -function DMM, and more, doesn't have tocost over $195.00. If it's a CircuitmateDM8OO.

Or, for a few dollars more, get true RMS(AC coupled) to let you accurately measurenon -sinusoidal AC waveforms, and all thecapability of the DM8OO, in the DM85O.

Of course, there's a whole range ofCircuitmate DMMs and service test instru-ments, including the DM78 autoranger that

DM25LCapacitance, Logic,hFE $99.95*TTL Logic Probe: 20MHz

Hi/lo/off indicationsDetects 25nS pulsewidths

Capacitance: 5 ranges(2nF to 201iF)

hFE (NPN or PNP):1 range (1000)

Continuity beeper

Built-in bail

Anti-skid pads

DM850True RMS41/2 digits. DCV accuracyis .05% +3 digits

True RMS

Frequency counter to200KHz

Data Hold displaycapability

Continuity beeper

Built-in bail

Anti-skid pads

Price: DM850 (TrueRMS) $219.95*DM800 (Average)

$195.00

fits in a shirt pocket, yet gives you a full size3' /2 digit, 3/8 " readout Not to mention acomplete line of am ssories like test leads,current clamps, even probes that can extendyour DMMs range and sensitivity. Alldesigned to work flawlessly with yourBeckman Industrial Circuitmate DMM.

See your Beckman Industrial distribu-tor and discover more DMM performance.For less.

'Suggested list price (SUS) with battery, test leads and manual.

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Ile km:m luduetrul,,'rp'!r.w,,c Inar.-nrr.t,....i. Products DivisionA Subsidiary uf Eon non hacrvtc Cungtanc3883 Ruffin Road, San Diego. CA 921231898(619) 495-3200 FAX. (619) 268-0172 TLX: 249031

© 198' Beekman Industrial Corporation

The how-to magazine of electronics...

GIGOTROflIDe

Volume 7, No. 12 December 1987

6Test your electronicsknowledgeBy Sam Wilson, CETThis month's quiz requires aknowledge of phase -lockedloops, ultrasonictransducers and silicontransistors.

12Locating replacementpartsBy Conrad PerssonYou've used all yourtroubleshooting skills andan array of test equipmentto isolate the problem with acranky television or personalcomputer. The end is insight...or is it? Often, theend of the struggle to locatethe defective part is just thebeginning of the struggle tofind a replacement.

20Troubleshooting thechopper circuitBy Homer L. DavidsonThe CTC131 chopper systemmay look simple when it'sbroken down into asimplified schematic, buttake a look at the completeschematic-not so simpleafter all. Here's a guide togeneral chopper circuits.

On the cover...Many suppliers, including compa-nies who are more commonly knownfor selling TV parts, offer a wideselection of replacement parts,tools and information. (Photo courtesy ofPhilips ECG.I

page 6GE's high -resolution, large-scale LCD,which has twice the sharpness of a

home TV screen, offers promise for TVtechnology.

page 12Finding the proper replacement partscan sometimes lead you on a wild goosechase. However, there are many compa-nies that can help you find the right re-placement for the job at hand.

Departments:4 Editorial8 News

10 Technology31 Prof ax53 Books58 Products60 Computer Corner62 Video Corner63 Literature64 Audio Corner66 Readers' Exchange68 Advertisers' Index

40Computer -aided circuitdesignBy Howard FalkDesigning a circuit can be along process - sketching,making calculations,building a prototype, seeingwhat performance you canreally expect. Usingpersonal computer softwareprograms, however, can giveyou a shortcut directly fromthe sketch to a workingcircuit.

46Tracking down remotecontrol problemsBy Conrad PerssonInfrared remote controls areconvenient electronicsaccessories, but anythingthat gets that much use isbound to break downperiodically. Knowing thepossible symptoms andprocedures can lead you toa fast repair.

54What do you know aboutelectronics? -A trip to thedeathnium trapsBy Sam Wilson, CETContinue last month's"fantastic voyage" into ablock of germanium toobserve deathnium trapsand how they affect thematerial's usefulness inmanufacturing diodes,transistors andsemiconductors.

2 Electronic Servicing & Technology December 1987

Some are famousfor missing parts,others forreplacing them.

Over the past fewyears we've made quitea name for ourselvesin the electronicsindustry. Techniciansworldwide know thatthe NTE diamondstands for the highestquality in replacementcomponents.

To distributors, we're known for responsiveservice, customer satisfaction and a broad product

line that includes flameproof resistors, capacitorsand static control products.With this kind of reputation for quality and ser-vice, it's no wonder NTE has become the fastestgrowing supplier of replacement components inthe electronics industry!See for yourself why NTE is famous for replacementparts. Our Technical Guide and Cross Referencelists more than 3,400 NTE devices cross-referencedto over 228,000 industry part numbers.To obtain your copy see your local NTE distributor.For their name and location just call us Toll Free.


ONE SOURCE. ONE CALL.

,p

NTE ELECTRONICS, INC.44 Farrand Street, Bloomfield, New Jersey 07003

Toll Free 1-800-631-1250 (Except N.J.) 1-800-624-2624 (N.J. Only)

FLUKE AND PHILIPS - THE GLOBAL ALLIANCE IN TEST & MEASUREMENT

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SMART PERFORMANCE

Autoset finds the signal at the touch of abutton. Philips' intelligent beamfinder auto-matically selects amplitude, timebase andtriggering for error -free instant display ofany input signal on any channel.

16kV CRT for optimum viewing. When itcomes to brilliance, clarity and spot quality,nothing in its class shines brighter.

LCD Panel for confident, at -a -glanceoperation. A valuable information center,it instantly displays all instrument settingsand parameter values. With no mistakes.

Auto -Triggering "thinks for you". This built-in intelligence provides fast, accurate, prop-erly -triggered signals up to 100 MHz.

IEEE Compatibility. The PM 3050 Series isthe only family of 50 MHz scopes with anadd-on IEEE -488 interface option for fastcomputer hook-up.

Choice of Models. Single timebase ordelayed sweep versions are available.

SMART SUPPORT

Philips PM 3050 Series also comes witha 3 -year warranty and all the technical andservice assistance you need. From Fluke-the people who believe that extraordinarytechnology deserves extraordinary support.

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December 1987 Electronic Servicing & Technology 3

Partsis

parts

There are few things morefrustrating than using your skills todiagnose a problem in a television,exercising skills honed over years ofapplication to desolder and liberate apart from the circuit, and then, whenyou try to order a replacement,finding that you can't get one. Thedistributor says it's on backorderfrom the manufacturer, or that it's aspecial part and he doesn't handlethat manufacturer's parts. Or youcontact the manufacturer and youfind that because that's a relativelynew product, there's no establishedlevel of spares and it will be a whilebefore there are any available; or yes,there are spares available, but theyrequire a minimum order of $50; orthey will not sell to you becauseyou're not an authorized servicingfacility.

For the time being, at least, yourefforts have gone unrewarded. Theset sits lifeless on the shelf. Not onlythat, but you now have more work todo: contacting friends, otherdistributors, mail-order houses to findout if there's anywhere you can find areplacement part.

Actually, in the overall scheme ofthings, this kind of problem doesn'tcrop up that often. But when it doeshappen, it overshadows the easy fixessimply because of the frustrationlevel and the inordinate amount oftime these problems take to correct.And, unfortunately, it happens oftenenough.

Not only that, but as time goes onit's likely to happen more often ratherthan less often. Take a look at thecurrent manufacturers' schematicsfor televisions, VCRs, CDs. In almostevery case you'll find symbols forintegrated circuits that contain anumber of complete functions. Forexample, I'm looking at one now thatcontains the video amp, noisecancellation circuitry, all of the AGCcircuitry and the sync detector.Another IC contains the FM detectorand the audio amp.

More and more often, for excellentreasons of design integrity andeconomics, whole chunks of circuitry

Editorial

that once took a couple of handfuls ofcomponents, yards of wire andseveral ounces of solder to puttogether are now manufactured inthe form of a tiny IC chip.

Some of these chips are standard,designed and manufactured by an ICmanufacturer and used by manymanufacturers. These ICs aregenerally available from a number ofsources, and if you can't find thespecific manufacturer's numberedpart, you can find an equivalent fromPhillips ECG, RCA SK or New Tone,much as you would find an equivalenttransistor, resistor or capacitor.

Unfortunately, in these days ofmassive mass production, it issometimes cost effective for amanufacturer to design a specialcircuit and have an IC manufacturerfabricate it for him. In such a case,lines of supply for replacements maybe narrow and finding a source forthe part might require some fancyfootwork.

Problems ordinarily occur at theend points of the cycle: at thebeginning before a demand level hasbeen established, and at the end asdemand is tapering off. Otherproblems occur with speciallymanufactured parts that areproprietary, when the manufacturerdecides to control the distribution ofthose parts. In that case only"authorized" servicers are allowedaccess to those parts. This hashappened recently with personalcomputers, and it causes a great dealof difficulty to other people who wishto service these products.

Still, the replacement parts supplysystem works pretty well in mostcases. If the demand for a particularpart is there, someone will find a wayto fill it and make a profit in doingso. (One place to look is the list ofparts suppliers on page 15 of thisissue.) If you're having difficultyfinding a specific part, it's probablyout there somewhere just waiting tobe found. Keep looking.


AWS MULTIMETERSDM -3000 31/2 DIGITROTARY SWITCH DMMJust one of three DMM's in our EconomySeries that combines quality with econ-omy. Features include built-in HFE,battery and diode testing; conductancefunction; 300 hour battery life; 10Adcrange; electronic overload protection onall resistance ranges; pocket -sized. (Alsoavailable models DM -1000 & 2000).Ranges: 0-200m/2/20/200/ 1000Vdc;0-200m/2/20/200/750Vac; 0-200p/2m/20m/200m/10Aac/dc; 0-200/2K/20K/200K/2M/20M 2 ; 1.5V batterytest 0-1000 Hfe test; 2K S2 diode test.DM -1000: $44.95/ DM -2000: $54.95 /DM -3000: $74.95

EZ-6111 31/2 DIGITAUTORANGING DMM

Unique and sophisticated in design,you'll find measurement taking a breeze.Loaded with features like autoranging involts and ohms; manual range selectionin all functions; diode test function; aud-ible continuity indication; normal and lowpower ohm ranges; 10Aac/dc range;overload protection on all ranges; 300hour battery life. Ranges: 0-200m/2/20/200/1000Vdc; 0-2/20/200/600Vac; 0-20m/200m/10Aac/dc;0-200/2K/20K/200K/2Mí2 ; 0-2K/20K/200K/2M11 Loft $104.95

DM -3010 31 DIGITPUSH BUTTON DMM

The standard in tough, job -proven digitalmultimeters. Housed in shock resistantABS plastic, you'll find safety was a primedesign consideration. Also equipped withoverload protection on all ranges; specialelectronic protection to 500Vac/dc onresistance ranges; UL1244 type testleads; normal and low power ohm ranges;10Aac/dc range; auto zero and autopolarity; built-in tilt stand. Ranges: 0-200m/2/20/200/1000Vdc; 0-200m/2/20/200/750Vac; 0-2001u/2m/20m/200m/2/10Aac/dc; 0-200/2K/20K/200K/2M/20M12 . $80.00

DM -6500 31/2 DIGITAUTORANGING DMM

This sensitive yet rugged instrument isloaded with features you'd expect to paymuch more for. The 6500 offers auto -ranging; low battery consumption; fuseprotection; safety test leads; audible con-tinuity buzzer; auto zeroing shock re-sistant housing. Ranges: 0-200m/2/20/200/1000Vdc;0-2/20/200/600Vac;0-200m/10Aac/dc; 0-200/2K/20K/200K/2M11. $99.95

DM -7010 4' DIGITROTARY SWITCH DMMHigh accuracy readings in the laboratoryor in the field. Features include 41/2 digit19999 max. display; built-in frequencycounter to 200KHz and conductancefunction; 0.05% basic dc volts accuracy;overload protection on all ranges; specialelectronic protection to 250Vac/dc onresistance ranges; UL1244 type testleads; diode and continuity tests.Ranges: 0-200m /2/20/200/ 1000Vdc;0-200m/2/20/200/750Vac; 0-200p/2m/20m/200m/2/10Aac/dc; 0-200/2K/20K/200K/2M/20Mí1, 0-200nSconductance; 0-20K/200KHz fre-quency. $179.95

DM -8010 31/2 DIGITROTARY SWITCH DMMThis easy to use DMM features a dc Voltaccuracy of 0.25% of reading; overloadprotection on all ranges; special elec-tronic protection to 500Vac/dc on re-sistance ranges; instant audible continuitybuzzer; UL1244 type test leads; auto zeroand auto polarity; diode test function;built-in tilt stand. Ranges: 0-200m/2/20/200/1000Vdc; 0-200m/2/20/200/750Vac; 0-20p/200p/2m/20m/200m/10Aac/dc; 0-20/200/2K/20K/200K/2M/20M52 . $84.95

DM -6592 ELECTRO-PROBE1M DMM

One of the smallest, most convenienthand-held DMM's you'll ever own. It'sboth autoranging and manual and is theperfect instrument for taking readingseasily and accurately in hard to reachareas. Other features include instant aud-ible continuity buzzer; one -hand opera-tion; electronic overload protection on allranges; data -hold button. Ranges: 0-200m/2/20/200/500Vdc; 0-2/20/200/500Vac; 0-200/2K/20K/200K/2000K/20M52 $70.00

DM -1 POCKET -PRO DMMBig features are packed in thispocket -calculator sized DMM. You'llfind autoranging, manual ranging,electronic overload protection on allranges, auto polarity, audible and vi-sual continuity indication, built-in testleads, "booklet -type" carrying caseis designed to fit easily in shirtpocket. Ranges: 0-2000m/20/200/450 Vac/dc; 0-200/2000/20K/200K/2000Kí t; 0-200f1 continuity. $34.95

A.W. SPERRY INSTRUMENTS INC.For more information see your local distributor or contact A.W. SFe ry nstrJraent: inc.

245 Marcus Blvd., Hauppauge, N.Y. 11788 800-645-5398 Toll -Free (N.Y. znd Alaska call co lec- 516-231-7050).Circle (10) of Reply Card

Test yourelectronicsknowledge

By Sam Wilson, CET

1. Ultrasonic transducers forfluid flow employ the __.__.._..._

principle.2. What. is the output voltagefor the transformer connectionin Figure A? V.3. What is the output frequencyof the phase -locked to:p (PLL)in Figure B? Hz.4. What is the output frequencyof the I'LL in Figure C?

Wilson is the ES&T electronics theory consul-tant.

5. The circuit. in Figure D isequivalent to

A. an SCR.B. a TRIAC.C. a Darlington.D. (None of these is correct.)

6. A silicon transistor is usedfor the Class A amplifier in Fig-ure E. What is the approximatevalue of the base current?7. What is the approximate val-ue of collector current for theClass A amplifier in Figure E?

8. Assuming the proper timeconstant., Figure F shows

A. an integrating circuit.B. a differentiating circuit.

9. Which of the following is areason for preferring aMOSFET over a bipolar tran-sistor in an RF amplifier circuit?

A. Low noiseB. Low input impedance

10. The number 2.7182818 isrepresented on a calculator as

Continued on. page 61

FIGURE A

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FIGURE B

FIGURE E

OUTPUTSIGNAL

Q + 20V

600kHz

INPUT

VOLTAGE -CONTROLLEDOSCILLATOR

FIGURE C

o

FIGURE F

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EVERY SONY PRODUCT COMESFULLY EQUIPPED WITH OUR

DEDICATION TO QUALITY SERVICE.

Your customers may never needTi -e Sony Service Company, but it'scomforting to kncw we're only aphone call away.

Our nationwide network of SonyService Centers, Training andTechnical Departments and our Nat-ional Parts Center -epresent ourccm nitment to service. This means ifyou sell or service Sony products,Scny is there for you. Read on to findall more.

1. Sony Service Centers. Repairwork is performed at over 27 SonyService Centers located throughoutthe country (even Hawaii).The Centers also sell Sonyaccessories Dnd rent videoequipment. For the nearestSory Service Center call(201) 930 -SONY (7669).

2.Regional Centers.Our RegionalCenters are set up to assist you withal)/ technical questions. Just call oneo: the =ollowing numbers. Mahwah,N.. (2c1) 529-16-6; Philadelphia, PA(215) 632-7999; rving, `X (214)258-1167; Fort Lauderdale, FL (305)920-5656; Honolulu, HA (808)834-6622; Niles, IL 312'i 647-0244;Detroit, MI (313) 477-4805; CostaMesa, CA (714) 549-4836, San Jose,CA (408; 280-7675.

3.Training & Technical Depart-ments. Because constant innovations the rule in the field of consumer

SONYSony Service Company

A Division of Sony Corporation of America

electronics, authorized servicers andSony Service Center technicians needthe latest information available. Thisinformation is provided through train-ing sessions at our Regional Trainingfacilities and publication of ServiceBulletins by cur Technical Department.

4. National Parts Centers. AllSony Service Centers, parts distribu-tors and authorized servicers dependon the National Parts Center. TheCenter also provides up-to-dateservice manuals and training tapes. Toreceive the Comprehensive ServiceLiterature brochure free of charge

write: Sony Service Company,National Parts Center, 8281NW 107th Terrace, KansasCity, MO 64153 AttentionPublications Departmentor call (816) 891-7550.

1987 Sony Corporation of America. Sony is a registered trademark of Sony Corporation.

UL proposes ANSI standardsUnderwriters Laboratories (UL)

is currently proposing severalsafety standards for recognition asAmerican National Standards:

UL 1412, the Standard for Safe-ty for Fusing Resistors and Tem-perature -Limited Resistors forRadio- and Television -Type Appli-ances, covers fusing resistors andtemperature -limited resistors foruse in radio- and television -typeappliances in circuits that do notinvolve potentials greater than2,500V peak. Mounting assembliesintended for use with such resis-tors are also covered. UL 1413, the updated Standardfor Safety for High -Voltage Com-ponents for Television -Type Appli-ances, covers flyback transform-ers, high -voltage multipliers, de-flection yokes and picture -tubehigh -voltage neck components in-tended to be employed in televi-sion -type appliances.

The proposed standard is a re-vised version of ANSI/UL 1413-82. UL 1417, the updated Standardfor Safety for Special Fuses for

Radio- and Television -Type Appli-ances, covers special types of fusesthat are not covered by separaterequirements and that are for usein radio- and television -type appli-ances where they are relied uponto limit power or current.

The proposed standard is a re-vised version of ANSI/UL 1417-82.

UL is seeking review and com-ment from interested individualsand organizations to help developa consensus upon which recogni-tion of UL 1412 by the AmericanNational Standards Institute (AN-SI) can be based, and upon whichcontinued recognition of UL 1413and UL 1417 by ANSI can be based.ANSI is a clearinghouse for infor-mation on standards and coordi-nates development of national con-sensus standards through volun-tary action.

Anyone interested should con-tact L.M. Cohen at UL, 333 Pfing-sten Road, Northbrook, IL 60062(312-272-8800, ext. 2693) and re-quest free copies of UL 1412, 1413and 1417.

EIA forecasts electronicsindustry growth in '88

The Electronic Industries Asso-ciation (E IA) is predicting that1988 U.S. factory sales of electron-

ic equipment, components and re-lated products will approach $238billion, or 6.2% over forecasted1987 factory sales figures. The as-sociation is also predicting that1987 sales will reach almost $225billion by the end of this year (5.3%over last year's total sales figure of$213 billion).

In examining the major sectorsof the industry, the EIA market-ing services department forecastsgrowth in these markets: Consumer electronics: Sales in-creases for 1988 are expected to beslightly less than in 1987, whichsaw an 8% increase over 1986sales in color televisions to U.S.dealers. Telecommunications equipment:Although 1987 sales are expectedto increase at a rate below the to-tal electronics industry (caused byfewer military orders), improve-ment is expected in 1988. Computer electronics: Comput-er industry sales are expected togrow 6% to 10% in 1987 and 10%to 19% in 1988. Electronic components: Salesare forecasted to reach almost $40billion in 1987 (up 6.4% from 1986,with a 20% increase in semicon-ductor sales) and to increase 8% to19% in 1988. E5U

The how-to magazine of electronics

ELECTRONICEditorial, advertising and circulation cor-respondence should be addressed to: P.O. Box12901, Overland Park, KS 66212-9981 (a suburbof Kansas City. MO): (913) 888-4664.Home office fax: 913-888.7243; Home officetelex: 42-4156 )NTERTEC OLPK

EDITORIALNils Conrad Persson, EditorCarl Babcoke, Consumer Servicing ConsultantTom Cook, Senior Managing EditorAlisa Carter, Associate EditorJoy Culver, Editorial AssistantDarryl) Fortune. Editorial AssistantDarren Sextro. Editorial Assistant

CONSULTING EDITORSHomer L. Davidson. TV Servicing ConsultantChristopher H. Fenton, Circuit Fabrication

ConsultantVictor Meeldijk, Components ConsultantKirk G. Vistain. Audio ConsultantSam Wilson, Electronics Theory Consultant

ART

Kevin Callahan, Art DirectorBarbara Miles. Graphic Designer

BUSINESSCameron Bishop, Group Vice PresidentEric Jacobson. PublisherGreg Garrison, Sales ManagerStephanie Hanaway, Promotions ManagerKelly Hawthorne. Promotions CoordinatorDee Unger, Advertising SupervisorCatherine Grawe. Advertising Coordinator

ADVERTISINGRegional advertising sales offices are listed inclassified pages.

ADMINISTRATIONR. J. Hancock, PresidentDoug Riemer, Circulation Vice PresidentJane J. Powell, Circulation ManagerJo Ann DeSmet, Fulfillment ManagerBarbara Clare, Reader Correspondent

MP

Member, Audit Bureauof Circulation

Member, AmericanBusiness Press

Member, ElectronicServicing Dealers

Association

ELECTRONIC SERVICING & TECHNOLOGY is the "how-to"magazine for technicians who service consumer electronicsequipment. This includes service technicians- field servicepersonnel and avid servicing enthusiasts, who repair andmaintain audio, video, computer and other consumer elec-tronics equipment.

SUBSCRIPTION PRICES: one year $18, two years $30 inthe USA and its possessions. Foreign countries: one year$22, two years $34. Single copy price $2.25: back copies$3.00. Adjustment necessitated by subscription termina-tion to single copy rate. Allow 6 to 8 weeks for newsubscriptions.

PHOTOCOPY RIGHTS: Permission to photocopy for internalor personal use is granted by Intertec Pubeshing Corp. forlibraries and others registered with Copyright ClearanceCenter (CCC), provided the base fee of $2 per copy of arti-cle is paid directly to CCC. 21 Congress St., Salem. MA01970. Special requests should be addressed to Eric

Jacobson, publisher.ISSN 0278-9922 $2.00 + 0.00

i/NTIERTLCPI/L/fMOrO CORIORAT/OM

' 1987 All rights reserved.


NEW TEK.PURE & SIMPLE.

Now, the perfect measure ofeconomy plus performance in alow-cost, 50 MHz scope backedby a 3 -year warranty. The new2225 exemplifies Tek quality at itspure and simple, affordable best.It's the easy, economical answerto your professional scope needsat bench and field sites, on themanufacturing floor and inthe classroom.

Two -channel, single time -baseTek basics enhanced by featuresof much more expensive scopes.Plus outstanding ease of use.You get 500 µV; div verticalsensitivity for low-level signals.Horizontal alternate sweep mag-nifications of X5, X10 and X50 fortime measurement accuracy. Newfront -panel Z-axis input. HF andLF Reject trigger filtering to sta-bilize noisy -signal displays. Plus

Bandwidth 50 MHzVerticalSensitivity 500 µV/divWaveformExpansion X5, X10, X50 Alternate

MagnificationsMaximumSweepSpeed 5 ns/divTrigger Modes Peak -to -Peak Auto, Norm, TV

Field, TV Line, Single SweepTriggerCouplingsWeightWarranty

AC, DC, HF Reject, LF Reject6.6 kg/ 14.6 lb3 -year on parts and labor,including CRT

5

TV Line and Field triggering. All ina compact, portable package.

Two heavy-duty Tek 10X modu-lar probes with a new ruggedizedprobe tip are included.

Scope. Probes. 3 -year war-ranty. 30 -day free trial. One freecall gets it all! Call Tek direct toorder, obtain literature or get thename of your nearest Tek repre-sentative or distributor. Technicalpersonnel can answer yourquestions and expedite delivery.Direct orders include probes,operator's manual, 30 -day freetrial on approved credit and fac-tory -trained service worldwide.Everything that says genuine Tek!

Call Tek direct:

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TeJctronbc

Copyright © 1987. Tektronix, Inc. All rights reserved TTA-706-1

Circle (11) on Reply CardWIMRTED TO EXCELLENCE

High -resolution LCDTV technology could ultimatelybenefit from research and develop-ment on flat -panel LCD displaysrecently conducted by GE. The GEResearch and Development Cen-ter, in a joint effort with the GEAircraft Instruments Department,has designed the world's largesthigh -resolution liquid crystaldisplay panel for aircraft cockpits.

The full -color, flat panelmeasures 61/4"x61/4". The LCD isless than three inches thick and re-quires a turn -on voltage of only15V. By contrast, the glasscathode ray tube (CRT) is 14 inch-es thick and requires 17,000V forturn -on.

The display owes its high resolu-tion to the large number of pixels(the dots that are activated to forman image) in its screen. The displayhas more than 2,800 pixels persquare inch (more than one milliontotal), which gives the LCD twicethe sharpness of a home TVscreen.

The high -resolution image is aresult of thin-film transistors posi-tioned at the corner of each pixel.Each transistor provides a switchthat turns the liquid crystalmaterial on or off at that point,enhancing contrast between lightand dark areas and improving theviewing angle. The transistorsconsist of a metal gate, a thin filmof hydrogenated amorphous sili-con nitride and amorphous silicon,and a metal source and drain. Thesilicon nitride and amorphous


silicon layers are laid down viaplasma deposition at relatively lowtemperatures of less than 650°F,which makes it possible tofabricate large arrays of tran-sistors directly on the glass plateswithout causing them to melt.

Liquid crystals are fluids thatflow like a liquid but have some ofthe optical characteristics of solidcrystals. They are transparent intheir normal state, but whenvoltage is applied, they becomeopaque, transmitting availablelight.

GE has sandwiched the liquidcrystals between two flat plates ofglass. The inner sides of the glassare patterned with silicon struc-tures that control the electricalcharges that "paint" the alpha-numeric characters or images onthe LCD's screen. A dimmablefluorescent backlight provides ahigh -contrast image over an am-bient brightness range from fullsunlight to the dark of night, andred, blue and green filters providea full -color picture.

The LCD is designed to meetmilitary specifications and can beprogrammed to display engineperformance, logistic and ballisticdata, altitude reference, radar im-ages and video. The European

rights to the technology arelicensed to Eurodisplay, a sub-sidiary of Thomson-CSF, France,and VDO Luftfahrt, West Ger-many.

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LocatingreplacementpartsBy Conrad Persson

The TV, VCR or personal comput-er is lying open on your work-bench. You've applied all your di-agnostic skills, probed with meter,scope and a handful of other testequipment, and you've finally iso-lated the cause of the problem -one or more of several parts on aprinted circuit board.

It's been quite a struggle, butvictory is in sight. You take thesoldering iron in hand and careful-ly liberate the troublemakers fromthe board. If life were fair, the warwould be won. All you would haveto do is locate the correct replace-ment in your inventory, solder it inand perform the smoke test.

Life is not fair, however. Often,the end of the struggle to locatethe defective part merely signalsthe beginning of the struggle to lo-cate a suitable replacement. There

Figure 1. Some linear IC devices thatwere originally supplied in 14 -lead DILcase are now available in 8 -pin mini -DIPcases. The pins 1, 2, 7, 8, 13 and 14 werenot connected in the original version, sothe 8 -lead package can be installed asshown.

Persson is editor of ES&T.

are the older units that have be-come obsolete and for which re-placements are no longer made.There are the manufacturers whorequire a hefty minimum order be-fore they'll ship any parts. Thereare the units for which you can'tfind any servicing information.And many times you either use auniversal substitute you have onhand or order a universal substi-tute and find that the pin arrange-ment is not quite the same.

This article, based on informa-tion, tips and hints found in partscatalogs from Philips ECG, Gener-al Electric, MCM, Motorola, NTE,RCA -SK, Workman Electronics,Zenith and others, is intended toprovide you with information thatwill help you find and select theright replacement part. It will alsosuggest ways to ensure that the re -

Figure 2. Some plastic -case devices aredirect retrofits for metal -case types. Justcut the center lead of the plastic deviceand bend the two outside leads.

placement does the job for which itwas intended.

RF considerationsAny time you substitute a uni-

versal replacement for an original -equipment component in an un -tuned amplifier stage operating ata low signal level (for example, theuntuned RF-amplifier [antenna]stage of the radio receiver, or alow-level AF -amplifier stage), itusually is not necessary to makeany circuit adjustments to assureproper performance of the equip-ment. However, when a replace-ment is made in a tuned RF-ampli-fier stage, RF-oscillator, converteror IF -amplifier stage, it is alwaysadvisable to check the alignmentof the associated tuned circuits toassure proper tracking and toachieve the required gain withoutloss of stability.

Considerations inhigh -power stages

When making a replacement in astage that operates at relativelyhigh power levels (such as Class Aand Class B AF output stages ofautomobile radios, phonographsand AF -amplifier systems), thetransistor bias should be checkedand adjusted, if necessary, to pro-tect the replacement transistorsagainst excessive dissipation andto minimize distortion. Means formaking such adjustments are gen-erally provided in the equipment,and the necessary instructions areusually given in the equipmentmanufacturer's service data.

Using replacements properlyWhen you install a universal re -

Í


placement in an FM tuner, TV tun-er or other circuit operating in theVHF or UHF regions, it is ex-tremely important not to changeany of the mechanical details ofthe original circuit. Before remov-ing the original transistor, careful-ly note its position with respect toother circuit components. Alsonote the lengths and placement ofthe transistor leads, and duplicatethese details as precisely as possi-ble with the universal replacementtransistor. If you don't do this, theresult could be improper tuning orcircuit instability, particularly inUHF TV tuners.

The same holds true for using re-placement integrated circuits inplace of an original -equipmenttype in FM radios and TV receiv-ers. Be careful to note the IC'sposition and lead placement.

Replacing 14 -pin ICsYou may run across situations

where a replacement IC for a14 -lead linear DIP (dual -in -linepackage) IC comes with only eight

leads. In this case, pins 1, 2, 7, 8,13 and 14 are not connected toanything internally in the package,so the 8 -pin package is a directplug-in replacement. The 8 -pin re-placement should be installed asshown in Figure 1.

Be careful withstud -mounted devices

When you're trying to replace astud -mounted device, it sometimesisn't possible to find a replacementwith exactly the same thread andstud size as the original. In this sit-uation, the device may be replacedwith a device that has the samesize or larger stud.

If you must use a componentwith a larger diameter stud, becareful that you don't enlarge themounting hole any more than1/64th of an inch larger than thereplacement component's stud. Al-so, the edge of the hole shouldhave a chamfer not exceeding0.01 -inch radius. It is also impor-tant that the mounting hole bedrilled perpendicular to the sur-

face within 1/10 of a degree. Youshould use heat sink compound be-tween the heat sink and the re-placement unit.

The mounting hardware usuallyconsists of a nut and either a pal ora lockwasher. Either type willwork as long as the proper torqueis applied. A good torque wrench isa necessity.

Replacing a metal -case deviceThe JEDEC TO -220 outline is a

direct retrofit for devices in theJEDEC metal TO -66 case. Like-wise, the CP-3 plastic device canbe used to replace types in theJEDEC TO -3 metal case. In eitherof these cases, you make the re-placement by cutting the centerlead of the plastic device and bend-ing the two outside leads to installthe device. (See Figure 2.)

Some other precautionsThere are many other precau-

tions to be observed in handling re-placement components. We willjust mention some of them here, as

Choosing an alternative vendorThe following are edited com-

ments from Gershon Cooper,president of ORA Electronics,suggesting how to choose an al-ternative parts vendor.

Many popular parts, particular-ly semiconductors for productsof Japanese manufacturers, arenow available from alternativeparts sources, frequently at pric-es below the manufacturers' pric-es. Many of these alternative sup-pliers stock a variety of replace-ment parts, plus other technicianaids, installer aids and accessor-ies. The semiconductors stockedare the same as those suppliedby the original manufacturer.Some unscrupulous companiesoffer surplus parts re -markedwith the part number, so careshould be taken when dealingwith replacement parts vendors.

How to choose a vendorMost alternative parts vendors

are catalog operations. The com-pany publishes a catalog that ismailed to service dealers. Thecatalog lists and describes allavailable parts and a phone num-

ber is provided to place the order.By looking at the catalog, review-ing the sales terms and condi-tions, and talking to the peopleon the phone, you can learn a lotabout the operations of the com-pany and then decide which com-pany will get your business.

Words of adviceDeal only with reputable com-

panies. If you receive frequentcatalogs or sales flyers, check tosee whether the catalogs/flyersare neat, printed on a decentpaper, and show clear pictures ofthe products. This will tell you alot about the reputation of thecompany.

Deal with companies that offertoll -free numbers. A toll -free num-ber is a good indicator that you'redealing with a large, establishedcompany. Deal with companiesthat offer you such services asfast delivery and on-line informa-tion on in- and out -of -stock items.Deal with companies that offereasy return privileges for unac-ceptable and defective parts.

After receiving an order from acompany, check:

1) How long it took for the orderto arrive. If the parts are cheap,but it takes a long time (morethan one week) to receive the or-der, then you are the loser.2) How are the products pack-aged? Paper bags, newspaperand other cheap materials can al-low the goods to be damaged.3) How much of what you orderedactually arrived? It should not beless than 70%.4) Is the invoice clear? Are allcharges reasonable? Avoid buy-ing from companies that chargefor handling or charge surcharg-es. Reputable companies chargefreight only in the amount chargedto them by the carrier, and nevercharge surcharges for credit cardtransactions or handling charges.Also avoid dealing with compa-nies that charge freight and othercharges on a percentage basis;i.e., $5 on orders up to $70; $10 onorders $70 and up; or 10% for or-ders up to $100, and 5% for or-ders $100 and up.5)1s your order accurate? Mis-takes do happen, but an exces-sive number of mistakes is aclear sign of a problem company.


many of them were covered in thearticle, "Replacement Parts," pub-lished in the June 1986 issue.Other problems to watch for, suchas ESD (electrostatic discharge),which was covered in detail in ourOctober issue, have been discussedin recent issues. To eliminate han-dling damage, use the followingprecautions: In order to avoid electrostaticdischarge damage to a static -sensi-tive replacement part, don't openthe static -shielding package untilyou're ready to install the part.Make sure you're wearing a static-

grounding wrist strap when youhandle static -sensitive parts, and,make sure your workbench is clearof any material that might be car-rying a static charge. With today'sadvanced technology sets, a lot ofthe components are static sensi-tive, so some manufacturers rec-ommend working at all times asthough the components you'rehandling will be damaged if youdon't observe static handling pre-cautions.

Use the right sized solderingiron and proper soldering tech-niques, and limit the amount oftime you hold a soldering iron incontact with the component'sleads. Most components are heatsensitive, and if you're not carefulwhile soldering in a replacementcomponent, you might destroy itbefore it ever sees service. If youthink a component might be dam-aged by heat even if you're careful,clamp a heat sink or pair of long -nosed pliers around the lead be-tween the component body and thesoldering point. This precautionwill dissipate most of the heatbefore it reaches the component. When working on a product thatuses surface -mount devices, don'tdesolder a surface -mount IC un-less you're absolutely sure that it'sdefective. These units are ex-tremely delicate and heat sensi-tive, and they will likely be dam-aged or destroyed by the removaloperation. And never place a sur-face -mount component that youhave desoldered back onto a circuit

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T2 -H7 -UM $295

Spindle/Elevator Gauge: The TSH gauge insertsinto the VCR just like a cassette. The new TSH-V5performs 6 critical measurements to eliminatetape binding and edge dam-age. This gaugequickly locatesproblems that can't even bedetected by other methods.Fully illustrated instructionmanual is included.TSH-V5 for VHS: $395

Video Head Protrusion Gauge: Universal, fast,safe method of measuring the amount of videohead tip wear. Measures inthousandths of an inch. Allowsaccurate predictions of re-maining head life. Head wearprovides useful informationregarding VCR condition andwear on other components.Stop guessing about headwear. Accessory "S1" standallows use on any VCR.HPG-1 $479 S1 $95

microns and ten -

Torque Gauge: A universal, inexpensive, accu-rate torque gauge for VHS and Beta VCRs.Calibrated in Gram -Centimeters both clockwiseand counterclockwise. Com lElir-plete with easy -to -follow, de- -tailed instruction manual forVHS recorders. Includes amodified VHS cassette forease -of -use.

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board. If you desolder a surface-

mount component, discard it. When bending leads to preparethe replacement component to beinserted into the circuit board, al-ways use a pair of pliers or anothermethod to hold the lead near thebody of the component to avoiddamaging the part.

Sources of replacement partsAlthough finding the right re-

placement part can sometimesseem like an impossible task, themore suppliers you're familiarwith, the more likely you'll be ableto find the part you need. Some ofthe suppliers listed in the accompa-nying sidebar sell through tradi-tional distributors; others sell viamail order. Check them all out.You might be surprised to findthat suppliers like Philips ECG,RCA -SK, NTE Electronics, Zenithand others who you thought soldonly TV parts can also provide youwith replacement digital ICs forcomputers, remote control units,test meters and more.

NEED PARTS...We can offer:* Large product selection*Fast & reliable service*Low prices*Quality productsWe stock: original transistors, ICs,

general replacement transistors,ICs, triplers, tuners, modules,picture tubes, audio & video cables,video accessories, connectors,fuses, lamps, plugs, jacks, switches,chemicals, CB accessories,resistors, capacitors, diodes, TVantennas, power cords, cassettemotors, audio & video recordingheads, styli & cartridges, telephoneaccessories, VCR belts & tires,technical aids, tools, testequipments, and many more.

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Circle (13) on Reply Card14 Electronic Servicing & Technology December 1987


Sources of replacement partsAbatron Electronics971 Ball Ave.Union, NJ 07083

All Electronics905 S. Vermont Ave.Los Angeles, CA 90006

Allied Electronics401 E. Eighth St.Fort Worth, TX 76102

Antique Electronic Supply1725 W. UniversityTempe, AZ 85281

Asti Magnetics32 Piermont RoadCresskill, NJ 07626

Circuit SpecialistsBox 3047Scottsdale, AZ 85257

Consolidated Electronics705 Watervliet Ave.Dayton, OH 45420-2599

Dalbani Corporation of America785 E. 14th St.Los Angeles, CA 90021

Dick Smith ElectronicsP.O. Box 2249Redwood City, CA 99063

Digi-KeyP.O. Box 677Thief River Falls, MN 56701

Digitron Electronics110 Hillside Ave.Springfield, NJ 07081

E.S.I.3171 Hempstead TurnpikeLevittown, NY 11756

Electronic Salvage Parts2706 Middle Country RoadCentereach, NY 11720

Electronic Parts Supply741 E. 14th St.Oakland, CA 94606

Electronics Warehouse1910 Coney Island Ave.Brooklyn, NY 11230

Etco ElectronicsNorth Country Shopping CenterPlattsburg, NY 12901

EVG1 Lee PlaceFreeport, NY 11520

Fox International23600 Aurora RoadBedford Heights, OH 44146

Fuji-SVEAP.O. Box 3375Torrance, CA 90510

GC Electronics400 South Wyman St.Rockford, IL 61101

Hitachi401 West Artesia Blvd.Compton, CA 90220

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Circle (15) on Reply CardDecember 1987 Electronic Servicing & Technology 15

Jameco Electronics1355 Shoreway RoadBelmont, CA 94002

Joseph Electronics8830 N. Milwaukee Ave.Niles, IL 60648

Matsushita Engineering & Service50 Meadowlands ParkwaySecaucus, NJ 07094

MCM Electronics858 E. Congress Park DriveCenterville, OH 45459-4072

Mid America Company2309 S. ArcherChicago, IL 60616

Milo Associates4169 Millersville RoadIndianapolis, IN 46205

Modal 1,011 FunctionGenerotor

Electronics'40thAnniversarySale!We are celebrating our 40th Anniversary byoffering you huge savings on B&K Test EquipmentIn addition to great prices, as an extra anniver-sary bonus you can get a $99.95 Cobra RacarDetector for only $40 when you purchase anyB&K instrument featured in this ad.

rend for FREE 480 page "IndustrialIProducts Catalog". I understand it is FREEwith any order or if requested oncompany letterhead. (Otherwise, $4.95to cover catalog and shipping costs)

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Model 2120 OscilloscopeDC to 20 MHz -Dual Trace 6"CRT tmvSensihviy

Reg. $479 $379.40MTN ANNIVERSARY POICE

Moral 2125 OscilloscopeSame great features os 2120except with delayed sweep

$469.4043T11 ANNIVERSARY PRICE

Model 1541A OscilloscopeDC 1) 40 MHz -Dual Trace -6" CRTInv SensitivityReg $845 $739.40

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Mocel 1803 FrequencyCounter 100 MHz -8 digitdispay-zero blanking ACor it tteryReg $186 $159.40

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Model 2005 RF SignalGenerator 100 KHz to 150 MHzin 6 fundamental bands and450 MHz in harmonics

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[ ] Rush merchandise per attached order.I understand rated accounts are shipped openaccount; otherwise send per credit card.Include $5.00 per item for shipping and handling Visa Master Card DiscoverC7 Check Money Order C] Rush CatalogCard No Exp. Date

Name

Company

Street Address

IL Res. 7% Tar Cm'? State lip

I

I

I

Mouser ElectronicsP.O. Box 9003Lakeside, CA 92040

NTE Electronics44 Farrand St.Bloomfield, NJ 07003

Nippon America9600 NW 12th St.Miami, FL 33172

OHM/Electronics746 Vermont Ave.Palatine, IL 60067

Omnitron Electronics770 Amsterdam Ave.New York, NY 10025

Optima Electronics2022 Tigertail Blvd.Dania, FL 33004

PanSon Electronics268 Norman Ave.Greenpoint, NY 11222

Pfanstiehl Chemical Corporation3300 Washington St.Waukegan, IL 60085

Philips ECG100 First Ave.Waltham, MA 02254

Projector Recorder Belt200 Clay St.Whitewater, WI 53190-0176

RCA Special Products2000 Clements Bridge RoadDeptford, NJ 08096

Richardson Electronics, Ltd.3030 N. River RoadFranklin Park, IL 60131

TEC83 E. Central Ave.Pearl River, NY 10965

Thordarson-Meissner628 Belmont St.Mt. Carmel, IL 62863

Unity ElectronicsP.O. Box 213Elizabeth, NJ 07206

Workman Electronics Products75 Packinghouse RoadSarasota, FL 33578

Zenith Svc., Parts & Accessories11000 Seymour Ave.Franklin Park, IL 60131 "en.

Cir^le (16) of Reply Card

16 Electronic Servicing & Technorogy December 1987

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230 Electronics Equipment Field Service Organization Personnel240 Service, Installation or Operation of Electronics FF1 1 Operations Management

Equipment In Industrial Or Commercial Facility Such as Service Manager. Operations330 Engineering Of Electronics Equipment In Manager, Production Manager. Customer

Industrial Or Commercial Facility Service Manager, Marketing/Sales350 Wholesaler. Jobber, Distributor Manager. Purchasing Manager, Credit/37t Electronics Equipment Or Components Accounts Manager and Other

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Copyright ©Tektronix, Inc. All rights reserved. PCA-329 1087

Troubleshootingthe chopper circuit

By Homer L. Davidson

All servicing technologies describedin this article are well known.Many of the tests commonly used(not mentioned in this article) arenot recommended for the CTC131. Ihave included only those tests thatproduce good results with littledanger of damage. The CTC131 isnot a suitable circuit for ex-perimentation. Just restore theoriginal circuit; don't change it.

A person can look at a simplifiedschematic of the CTC131 choppersystem and think, "That circuitisn't so difficult; I can understandhow all of it operates." Very true.But that is only because it has beengreatly simplified; the completecircuit is nearly incomprehensible.Many resistors were added forvoltage drops and current limit-ings. Diodes were added as

switches, as rectifiers and as vari-able resistors. Many capacitorsfrom small to large capacitancewere included for a variety oftasks. A close -packed arrange-ment of capacitors, resistors,diodes and zeners completely sur-rounds U401, the regulator -control IC. Any one of the func-tions (which usually involves onepin of U401) can be traced andeventually understood, but it is dif-ficult. And the difficulty is in-creased by the cross -coupling be-tween circuits. My advice whenyou're servicing this power supplyis to use the full schematic.

The largest addition to the chop-per's simplified schematic is U401,the regulator -control integratedcircuit. The following are severalof its functions: Monitor the high voltage (HV)

and shut down the chopper if theHV rises too high.

Monitor the + 129V supply, us-ing it to regulate the do voltagesproduced by the supplies pow-ered through T105.

Monitor the + 12V supply. The pulse -width -modulation sys-

tem produces the variable -widthpulses that are emitted fromU401 at pin 4. These pulses arerectified for the regulated powersupplies.An internal oscillator is locked to

the television horizontal scanningfrequency to avoid beats.

Regulation in this type of systemis accomplished by varying thepulse widths. When narrow do

The technician is testing bridge diodes from the bottom of the circuit board. A DMMspecial diode test is used on the four bridge diodes of the + 150V hot supply.


Davidson is ES&T's TV servicing consultant.

pulses are integrated, the result isa low de voltage. As the width ofthe pulses increases, the do outputvoltage increases proportionally.

Voltage regulation in the CTC131can be summed up in this state-ment: When a higher de outputvoltage from T105 is needed, thechopper pulses are widened, pro-ducing a higher de output voltage.

Complete servicing of theCTC131 chopper and power-

supply circuits is a complicatedprocedure. Fortunately, manyrepairs can be performed aftersimple measurements and thereplacement of a few components.

In most TV receivers, thehorizontal -drive and horizontal -output transistor areas receivemost of the attention during pre-liminary testing. This is not thecase with the CTC131, where thechopper stages are the most likelyto fail; therefore most of the testsinvolve the chopper.

The power -makers (and thustrouble -makers) are shown in theblock diagram. They should be thefirst tested when F100 in Figure 1is found to be blown.

This schematic was carefully ar-ranged so the areas of hot acV wir-ing and cold acV grounds areclearly differentiated. Everythinginside the dotted rectangle is hot.Notice that each of the four trans-formers has one or more hot acVgrounds on one side via one ormore windings, but they also havecold acV grounds at the other sideof the same transformer. This isnot a new application for trans-formers. Power transformers, with120Vac on one side and severalsecondary windings, became popu-lar. These cold chassis modelswere greeted many years ago as amajor advance in safety over themethods of using rectified 60Hzpower without isolation.

Actually, all the CTC131 60Hzwiring (less the degaussing circuitand the tuner power) is containedin the center area of Figure 1.Remember that T101, T105, T103and T104 are the four trans-formers with hot primaries andcold secondaries.

Because there is so little 60Hzhot wiring, it appears out of bal-ance to give that much detail aboutthe subject. Yet it always has been

U101PYM

TO OVERCURRENT1104

PROTECTION -.---

COLO 1GROUND'

F100 R109SA 2.7

FUSE l

DGE

'1"NEC 1F1ERBRI

L.

0100TURN OFF

HOT

GROUND

.150V

CHOPPEROUTPUT

B. i150V

CAUTION:HOT GROUND

1101

p MSC

TUNER

T105CHOPPEROUTPUT

DIODESANDFILTERS

.129VSUPPLY

.210SUPPLY

*16.5VSUPPLY

-240SUPPLY

Figure 1. Most of the CTC131 hot 120Vac wiring is contained in the circuits and com-ponents inside the area bounded by the lines of large rectangles or blocks. All otherwiring uses cold grounds.

part of RCA service meetings.Therefore, hot/cold grounds mustbe important. Although theCTC131 is not the first RCA tohave hot/cold double grounds, it ismuch more complicated.

An incorrect connection for aquick test on this set is more likelyto cause damage than a similarmistake with an older model (onewithout a chopper).

s. rCircuitdescriptions

If you work with these CTC131chassis without studying the cir-cuitry, the relative failure ratemight seem to indicate that thechopper transistors are weak orare just prone to shorting out.Many of the failures end with theQ101 chopper transistor shortedbetween all pins. Unless someother components are replaced,the new transistor will be ruinedalmost instantaneously whenpower is next applied.

Did you know that the chopper isforced to control the largestamount of power of any transistorin the chassis? The output of thechopper supplies four de voltages.One of those voltages is + 129V,which is the regulated B + for the

horizontal -output transistor's col-lector. The other chopper -regulated voltages (+ 24V,+ 16.5V and - 24V) power most ofthe circuits remaining, helped in asmall way by two B + supplies rec-tified from flyback transformerpower.

A full list is not necessary to seethat the power load carried by achopper transistor is much higherthan that of any horizontal -outputtransistor. Later, the circuit andcomponents that reduce the dissi-pation of the chopper will bediscussed.

The schematic condensedSeveral items should be dis-

cussed before leaving Figure 1.Notice that there is no on/ off switchon the schematic. That's becausethere is none for the TV function.The 120Vac is applied continuous-ly, and the + 150V voltage is alsopresent, waiting with zero currentand maximum voltage for thechopper channel to be activated.

T101 is called the standby trans-former because it operates 24hours a day to power the tuner -control module, even when thetelevision is off. It is a smalltransformer, mounted on thechassis at the rear. The windingswill feel warm after several hours


REGULATIONCONTROL

HOPI)PULSES

R430100

C416IPF

0401

8.

REG. DRIVER 3.3

CR409

C4171 p

R426

0401 CHOPPER DRIVER

tCR408 R451

IOK

3 T

1.12.30

C415 .16.00

tlI

6.50 TO OVERCURRENT T104

SHUTDOWN

OPEN1103 \ R102 OPEN

CR108

OPEN-CHANGGEED

` R10347

61062.2

COLD ¡,ROUND

CR105

C11Á2 OPF

0100CHOPPERTURN-OFF

0101 CHOPPER OUTPUT

1 T 05áLEAKY

R107

<HOT GROUNC:

SHORTED

2

.1500HOT

CR413

CR415

71.400

.1297SOURCE

C45222008F

CR414

C4432PF

.240SOURCE

TP402

C4S6680Pf

CR416

TP401

r TO 165VSOURCE

C45122011F

7P404

TO 12VSOURCE

TO -240SOURCE

Figure 2. These components are sufficient to make up an operable circuit, although many of the less important resistors andcapacitors have been deleted. 0100 and 0101 have the largest failure rate of all components.

of operation. (T101 is not shown inany of the photos or schematics.)

Also, ac power is taken from thecold T101 secondary. After rectifi-cation by CR406 and filtering byC463 (220µF), the result is a stable+ 12.3V that is always available.This + 12.3V source powers theoscillator and other essential sec-tions in U401. Without it, start-upwould be impossible.

Some of the following can bechecked only by studying a com-plete schematic. When the frontpanel on/off button or the remotecontrol on/off button is pressed,the tuner -control module deliversa logic low that reverse -biasesCR426 in the overcurrent-shutdown circuitry. This starts thepower supplies and chopper intooperation. However, the low is justa short pulse, and the operationwould soon stop except for + 30V,which is produced by rectificationof flyback pulses. A sample of the+ 30V is fed to the tuner -controlmodule and a certain IC that

latches the on/off line to a steadylogic low state. This information isnot shown in Figure 1, but wemention it here to explain how thetelevision can be turned on withouta conventional switch. (The chop-per area in Figure 1 is explained indetail later, along with accompa-nying schematics. Therefore, theexplanations will be general innature until then.)

The width of the pulses producedin the pulse -width modulated(PWM) area of U401 undergoesconstant changes as part of theregulation process. The pulses thenexit at pin 4 before being sent tothe base input of Q401, thechopper -driver transistor.

The next stage would appear tobe a normal transformer -coupledamplifier except for turn-off tran-sistor Q100. Notice that Q101 isthe only load connected to the hot+ 150V supply. After diode rectifi-cation and filtering, four second-ary windings on T105 producethree major B + and one negative

supply. (These are discussed later.)Also, the bridge rectifier consistsof four separate diodes.

PWM and the chopperAs shown in Figure 2, the PWM

chopper -regulated power supplyconsists of three transistors, threetransformers and one IC regula-tion control.

Values of a paralleled resistorand capacitor at U401 pin 3 deter-mine the free -running frequency(about 15kHz) of the regulation-

control RC oscillator. Locking isaccomplished by horizontal pulsesbrought from T401 flyback toU401 pin 8. The locking is neces-sary to prevent beats and interfer-ence that could occur if the fre-quencies were different and thechopper signal radiated into thetelevision signal circuits.

At U401 pin 4, the output signalof the regulator control (whichconsists of segmented, variable -width pulses) is capacity -coupledto the base of Q401, the chopper

OPEN

F100 íL100SA

120VAC

OPEN

R1092.7

CR100 CR103

BRIDGE

CR102

LEAKY

+150VHOTSUPPLY

C1002011

HOTGROUND

OPEN1103 '\ R102

REG. DRIVER 3.3

OPEN 0101 CHOPPER OUTPUT

CR108 1 1105

OPEN -CHANGED

` 610347

R1062.

1104

CR105

C1142 OPF

t0100CHOPPERTURN-OFF

A./LEAKY

R107

(HOT GROUND)

SHORTED

2

+1500HOT

Figure 3. Fuse F100 (5A) and R109 (2.70) will be blown by ex-cessive 120Vac current. Resistor R109 is a special numberand is soldered into place, so it is best to find the problemwith the 120Vac power turned off, if possible. Test all fourbridge diodes in -circuit for both forward conduction andreverse -polarity leakage, then continue the tests.

Figure 4. Circuitry between 0101, T103 and 0100 is the centerof attention because most of the chopper -componentfailures occur here. If Q101 is shorted, test R102 and R106. Ifthey are open, the new Q101 installed will be destroyed in afraction of a second after power is applied.


driver transistor. Following ampli-fication in Q401, the waveformfrom interstage transformer T103is applied to the Q101 chopper out-put's base. Also, Q100 has a func-tion, as explained later. The Q101chopper collector is connected tothe T105 chopper transformer,and the pin 2 end of the T105 wind-ing connects to hot + 150V (nearlythe only load on the + 150Vsupply).

According to scope waveforms,the theoretically perfect square -cornered do pulses at the Q101 col-lector are more like roundedpulses. These rounded pulses passeasily through transformer T105primary, producing voltages in thefour secondary windings. (SeeFigure 2.) The highest do voltageis + 129V, which supplies thehorizontal -driver and horizontal -output transistors with de power.Also, the + 129V is used in thevertical -output stages. A sample ofthis voltage is provided to thevoltage comparator inside U401for regulation and shutdown in theevent of excessive high voltage.This + 129V is rectified by diodeCR412 and filtered by capacitorC443 (2µF).

The winding between T105 pins4 and 5 produces + 24V after recti-fication by diode CR415 and filter-ing by 2,200µF C452. The +24Vsource powers the audio -outputstage and all the remaining sec-tions of the vertical sweep. Thewinding between pins 3 and 7 pro-duces + 16.5V after rectificationby CR414 and filtering by 680µFC456. The + 16.5V supply fur-nishes power for most of thesignal -processing circuitry, theaudio circuits and a few other

T105, the chopper -output transformer, ispointed out by the end of the pen. 0101is mounted just to the left and on a ver-tical panel, with the 0101 terminals andsocket side shown.

tasks. Also, by zeners and avoltage regulator transistor, the+ 16.5V supply is parent to + 12Vand + 11.2V source 1, source 2 andsource 3.

That terminal 3 to 6 winding hasthe ground at the top, implyingthat the polarity is reversed, whichis correct, because it is feeding anegative supply. After rectifica-tion by reversed CR416 and filter-ing by 220µF reversed C451,- 24V is produced. The - 24Vsource is used mostly as a refer-ence for the automatic kinescope -bias circuitry. Evidently, very lit-tle current is needed.

Overcurrent shutdown in theCTC131 is much more complicatedthan it is in most television re-ceivers. Emitter current of theQ101 chopper -output transistor ispassed through the primary oftransformer T104, with 112 resistorR107 paralleling the primarybefore the current returns to hotground. The transformer second-ary signal is filtered andamplitude -reduced before it joinsthe part of the circuit that is usedfor turn -on (when CR426 is low).From there the combined signalsgo to U401 pin 9. Notice that allthe circuits from the secondary ofT104 on to pin 9 have coldgrounds. When the Q101 currentexceeds a certain value, the over -current shutdown circuit is ac-tivated and the chopper operationceases.

Chopper turn-off operationMention was made previously of

the turn-off operation. Here's howQ100 operates. (Refer to Figure 2.)

CR108 and 3.311 R102 are inseries between the Q101 base and

Q101, the chopper -output transistor(pointed out by the pen), is mounted on avertical panel, so this is the view fromabout the center of the chassis. Thesocket and pins are on the other side.

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The chopper turn-off transistor Q100 is located at the end of the pen. Q100 issoldered to the circuit board. All chopper transistors (including 0100) should bereplaced only by new ones with original part numbers.the top terminal of T103's second-ary winding. When that top ter-minal is positive, CR108 will con-duct through R102 and present aturn -on current to the Q101 base.

At the same time, an instantane-ous negative voltage from the bot-tom terminal forces CR105 to con-duct, and this charges 220µF C114with about - 2V relative to theQ101 emitter. (Notice that thepositive lead of C114 connects toQ101's emitter.)

When polarity of the input/drivevoltage reverses, diode CR108conduction is turned off, and thepolarity of the bottom terminalforces the emitter/base junction ofQ100 to become forward biased.Therefore, Q100 saturates, pro-ducing reverse current flowthrough R106, which removes thestored charge in the emitter/basejunction of Q101 to make certainthat the Q101 transistor currentturns off quickly.

If the receiver is operated whenthe Q101 chopper has a problem inthe Q100 area, Q101 will heat up

excessively. Above a certain over-load point, the transistor will shortand the 5A fuse (F100) will beblown. Unfortunately, by this timeseveral components are likely tohave been damaged. The criticalones are: R106, R102, R103 andCR108, plus transistor Q100 chop-per turn-off. Of course, the Q101chopper transistor carries thelargest load and is subject to exter-nal overloads that cause Q101 toshort.

Commonsymptoms

If the symptoms are no pic-ture/no raster, measure for the+ 129V collector voltage at thebody of the horizontal -output tran-sistor. This shows whether or notthe chopper power -supply circuitsfrom T105 are normal. If zero (orvery low) do voltage is measured atthe horizontal output, test theQ101 chopper -output transistorcollector voltage at the case.

Circle (19) on Reply Card24 Electronic Servicing & Technology December 1987

(Remember, the negative testprobe must be touching the hotnegative terminal. The correctvoltage is hot + 150V, but if thechopper case checks zero volts, ormuch lower than + 150V, test thefour diodes of the bridge rectifier.A convenient hot ground for thesetests is the negative terminal ofC105. Notice that the + 150V teststo hot ground, but the + 129V sup-ply tests to cold ground. Specifictests for the bridge diodes are sup-plied later, along with additionalschematics. And of course, thefour basic de voltages produced byrectification of T105 pulses canserve as checkpoints where a fewminutes spent in testing can pro-duce at least four voltages foranalysis. These checkpoints are:TP400, TP401, TP402 and TP404.(See Figure 2.)

Figure 3 shows such major com-ponents as the bridge rectifiers,the F100 fuse, and the R109 surge -limiting resistor. The fuse andresistor usually must be replacedany time a shorted Q101 chopper -output transistor is replaced.

the fuse andlimiting resistor are there for pro-tection (although the resistor hasother functions). Therefore a list ofcombined symptoms can be help-ful. For example: Sometimes when the chopper

transistor is only leaky, the fusewill not blow.

A shorted Q101 chopper outputand a shorted horizontal -outputtransistor occurring at the sametime will blow the fuse and R109.

Usually both the fuse and R109will be opened by overload froma shorted or leaky bridge diode,or a shorted Q404 horizontal -output transistor along with a

shorted flyback transformer.A low -resistance reading across

filter capacitor C105 in the + 150Vhot source often indicates ashorted Q101 chopper transistor.Measure the resistance from thebody of Q101 to chassis ground(and also hot ground). Thenremove the chopper Q101 outputtransistor from the circuit andmake the same measurementagain. If the second reading ismuch higher, this could indicateleakage in Q101. Next, test Q101.

Continued after case histories.

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Dead television-nopanel lights lately

In this CTC131 RCA, the chassis was comp

dead. None of the LED indicators on the front

panel could be lighted. Itraasur ds case

dc vroltage

at the horizontal-outputeat thecollector, andutputhscollllector. Both

d thereadingsindicated

chopper -output's F100 was blown, but when it

awas replaceed

andpro

the.replaced and receiver mo edrthe 0101ed on the

second time, it blew again.

chopper -outputtransistor from the circuit and

found leakagebetween all three elements.

No B+ wasmeasured at the 0101 c1

hpper50hotshould

collector after it wasreplaced. A B +

the

thereit.An all times whenQmeasurement ac101

is outross the

bridge

ac voltagesindicated open circuit that was

bridge rectifiers indicatpower. 109, a 2.7Q 15W

eliminating the 120Vac p

resistor, tested open in the ac circ0

fuse,uit.

bedFigure

Replacement the ransiiistor brought the receiver0101 chopper-output er problem.to life and Rd10a9 shoulder hnever be replaced with

Incidentally,a large -wattage resistor that has a resistance o f

less than 2Q. Not only is the resistancecritical, but

the resistor constructionmust be right for self-

destructionresistor does not fitthe specifications a

current is dnd wouldnormal.A

aproper protection. R109

leave the television of the degaussing board.

is connected to lugs__ --

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Chopper destroyed repeatedly front

Symptoms of the CTC132 chassis werea

etar

light that came on, then the sound)

large and everything(picture and

indicator replaced,en

dead. The 5A F100 and 0101 were repswas

went same after power

bgt the operationd. Tn was thethe replacement

0101 had

again applied. This time,collector andQ1t can be checked for

emittera terminals.

shortb

hecke case for the

terminais. using ground. A low -

resistancepositiveaod

sher InCir byfiltercapacitor

andreading

hot1Q

acrlos0101 chopper-output

0105 indicatesa shorteder

transistors,tranoiptev several chopper

To prevent ruining theerr's line

usea variablewith

linervoltage perhapsras you

voltage.Start with a

line voltagechopper -output

monitorSlowlyelincrease

thea0101voltage at the

collector. If the choppercircuit isthe low

transistor'swill remain

low and

defective, the transistor voltage warmly as

the 0101 chopper transistorwill operate

the ac voltage is increoasedts in the base circuit of

Check out suallspectingcomponents

overloaded thesecondarT 05y0101normrre Overloads in

cause sometransformer

problems.

in 0101 chopper, but excessivetransformer

circuits will usually

overheating the 0101 transistor.

overloads0100

destroy

The chopper turn-off traitor was tested

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leaky between all

was found to be to thepit and moved

three pins. This transistor dmust beecty

large to board. position, so the connecting

cablesa

the servicingloosened where provided.0100 and F100 (5A),must bewith

theAfter replacement restored along

the low voltage wasTV performance.

0100 and 0101 destroyed the rasterbut only for a

In another ng with normalssoundreceiver,

appearco along blown, butfew seconds. Then all F100 was not

ad,blown,

including the panelo light.voltage at the collector

of thewas

there was nout transistor. The Qjp1 chopper as

choPp0100

replaced, but replaced

chopper

went out immediately.0101were rep ace

thehesame time,

-off transistor the same results-bothEach transistor tested

awere destroyed

lemr ntsleakages or shorts betweeQg0of óPPlements.

Attentionshifted to the input -dcirivercuit of

but were normal. All windings of

transistor.It and all diodes in the

transformerswere tested, T104 were testede forsistors were

transformers the 0101 base

checkedresistance. Finally, open. These resistors

and found t47Q R1Ó3. Remember the

were 2.258106 and

values and the circuits becausethese are typical

troubles. (SeeFigure 4.)

8106 and R103,

aboutQ100, Q1Q1, and

replacementof 35Vac

After rep reducedthe line voltage was chassis started to work

slowly increaseduntil the

previously,the most frequent

at 120V ac.0101 chopper output

As noted P . is theoff transistor,component

ía00, thelure chopper turn-offhave visible

transistor.allur that mig blown apart

symhas many fa¡ in this machine was pins.

0100 base and collectorhad open are R106, R102,

and, of course, that fail often

Other components CR108.8103 and sometimes

petlection problems-0101 destroyed

in the horizontal-output

Suspectproblems and found

when the 01Q1 choppere tested andcircuits ut transistors transistors, but use the

horibe

shorted. lace increaseshorted. transformer to

slowlythe lineto se line -voltage 35Vac.

voltage from to about 60Vac, the,Tight

the input ac slowly up (at 120

be

voltage is increasedvltage of + 129V c. If theercted bout +65V at 60Va +4V,

chopper-outputto rise to a only to aboutvoltage rises cases of both

chopper output feel the feel warm,they are

turn off the power and

If both transistors have to be

transistors. the search someoverloaded,

and

appropriateto consider Veform

continuedime it is app Insufficient drive waveformAt this areas. _

possible trouble

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source at 0400 horizontalIC can

causeo

the + 16.5V transistor to draw

excessivethe centhorizontal-output401flyback with shorted

s or a shorted componentin the output

excessive current.A

e both the 0404

ciwinding 404 might damage the 0101

chopper -

outputhorizontal -output

of 0ut transistor and

horizontal-outp ed leakage in

output transistor. ut stage),Several CTC13sistor

chassis develop

438 (of the horizontal -output st-output

whichcitor

C both horizontal- and 16putruined lace the capacitor

with the 1372

transistors.Replace or a substitute

of precise

original Part nom1,200V rating. fl back had

caonetance

sasd C438 and heted 0100, 0101,In chassis, very leaky

0404,0400.

is andflybato find a

(1404,flyback in addition to a

C438 capacitor.

Unusual locking problemoperation,

the picture would

After a half hour of op M first, the

begin to pull and tear horizontally.increasingthe in9be eliminated cry in re a dark

thei couldevirtually pull andthe brightness

and contrast.

screenappeared, the picture would Ó crated for

After the set had operated atunstable.picture showed excessive contrast

two hours,all times regardless

of the brig

levels.

I found that

removingthe back cover, the Q4Q4

After reh previously replaced er turn -

someone ut transistorand the Chopp

Q100. The 0100chopper-turn-off

horizontal-outputwith a

different typeoff transistor replaced

iagain withthe correct

transistorhad been P 0100oiling

of transistor.Replacing the picture P

part number142251 solved

and controlsproblem completely.

Becausethere are CTC131-132

chassis, try to

to the RCA cabinet, if

connected chassis is in thein the

service it while the chassis to the

possible.Move the provide

more room.

servicing Positionto

ave studied the many of

cirTechnicians

whond have serviced

explanationsand test)

havethem

cults extensivelyfind the aexP 1e. However,

them m¡g be rather simple.techniques tt the CTC131

tests to the tests and

tried to adaptthat have been found useful for

yearsi

techniques0

servicingof TV receivers

that are two

old. in the CTC131 are oftensolved

lve transistor,

y

Problems 0101 chopper-outputhops slimes

replacementof the8106 resistor. Sometimes

the R102resistor pae -td urn off transistornents repairs an

a new 0100 Chopp few compReplacement

of theseof the dead receivers.

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Continued from page 25.A diode tester or the diode func-

tion of a digital multimeter can beused to test individually each sili-con diode of the bridge. In additionto the usual hazards of large -current diodes, these diodes mightbe damaged by weak lightningstrikes or strong overloads (suchas a shorted Q101 or horizontal -output transistor). These bridgediodes could become shorted orjust leaky.

For an accurate test of diodeleakage, disconnect one lead ofthe diode during the tests. If theDMM gives any hint of leakage,change to a VOM on a higher -resistance range. This reverse -polarity leakage -resistance read-ing should be very high for thesediodes. If there is doubt about adiode, replace it. Use 3A ratingdiodes for replacement. (Inciden-tally, if the RCA 2.70 15W R109resistor cannot be obtained, re-place it with two paralleled 5(215W resistors. However, the genu-ine article is recommended.)

C438 (which the technician is pointing to) is a part of the horizontal -output circuit.When C438 is shorted or severely leaky, it might destroy 0100, 0101, 0404 and U400.

Finding the componentsHere are the locations of these

input ac circuit components: R109is mounted high on the degaussing

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board; fuse F100 is plugged intosnap clips near the back at aboutthe center of the chassis (easy ac-cess); the large C105 filter capaci-

tY-

r -7I

in"ATRIX, INC 14221 Ewing Avenue South Burnsville, MN 55337

(51 2) 894-6154 1-800-222-6154 FAX (61 2) 894-6256 Telex 91 024001 39Circle (25) on Reply Card

December 1987 Electronic Servic,ng & Technology 29

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tor is near the right -to -left centerand about 25% from the rear of thechassis; and the bridge diodes arescattered in a "southeast" direc-tion on the circuit board nearC105.

If the + 150V hot supply at theQ101 collector measures almostzero voltage (compared to hotground), but the four bridge diodeshave been tested and finally re-placed with new ones without im-provement, then where do youlook? Few components remainuntested.

Assuming that you have testedC105, two items remain untested:continuity of the power wiring andthe actual 120Vac line voltage.Figure 3 shows all the basic ac wir-ing except the noise filter, L102.Unplug the power and check thepower wiring with an ohmmeter.Then, reconnect the power andcheck for 120Vac using the DMMac function. The 120Vac mustreach CR100 and CR101 cathodeswhere the voltage can bemeasured.

When the fuse continues to blowIf you've done everything you

can think of to repair the set, butthe fuse blows every time you turnthe set on anyway, here's how toprotect the fuse and the TV cir-cuitry while you probe further.Remove the fuse from its holderand connect a 100W incandescentlight bulb in its place. Theresistance of the bulb limits thecurrent that the television candraw to a safe level, while itsbrightness gives you a visual in-dication of the amount of currentbeing drawn: If the bulb is bright,the television is drawing high cur-rent; a dim bulb means the currentdraw is low.

In one CTC131 I encountered,the first test with the bulb/fuseshowed a bright bulb. I removedthe horizontal -output transistormounting screws (to disconnectthe B+) and the light became verydim. These symptoms pointed toserious problems in the high -voltage and deflection sections.

If the test just described resultsin a bright bulb during both condi-tions, the next step is to removechopper -output transistor Q101. Ifthe bulb then becomes dim, Q101 is

shorted or something is drawingexcessive current from one of thefour T105 voltage supplies.

If the bulb remains bright and noobvious defects are found, the nextstep is to check all four bridgediodes; DMM and VOM tests of thediodes were described earlier. Cer-tain types of diode leakage varywith the applied voltage. There-fore, a VOM often would show aleakage reading where a DMMwould not. An initial test of thediodes can be made in -circuit(without disconnecting any leads).Of course, replace any diodes thatshow leakage.

Also, check the resistance ofC105; it might be shorted or leaky(notice the hot ground).

Problems in T105 voltagesupplies

In addition to defects in thechopper driver and output stages,it is possible for problems in one ormore of the four do suppliespowered by T105 to develop fromshorted, leaky or open diode rec-tifiers or filter capacitors. If theoverload is heavy enough, it cancause chopper shutdown.

Check the silicon rectifier ofeach voltage source. This can bedone rapidly with the diode test ofa DMM. Normal readings forCR413 and CR415 are about0.458V with overrange readingsdisplayed for the other polarity.

When CR414 is given the diodetest, the result might be 0.430V inone direction and 0.650V in theother direction. These test resultsare normal, because the + 12V regu-lator provides a low -resistancepath in one direciton. If there isdoubt, disconnect one end of eachdiode and test the diode as if it isout of circuit.

Resistance readings for testsShorted or leaky components in

circuits connected to differentvoltage sources can cause thechopper power supply to shutdown or drastically reduce the out-put voltages. After you've testedthe major components of thepower supply, take a few ohm-meter readings of the resistancesof the various voltage supplies tocold ground. You might discover

Continued on page 39.Circle (26) on Reply Card


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51

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Computer -aidedcircuit designBy Howard Falk

When you're designing a circuit,after you sketch it out your nextsteps are probably to make a fewrough calculations, then start tobuild a breadboard. When the com-ponents are connected and thepower is turned on, you get yourfirst look at what has to be changedto actually make the circuit work.

If you have a personal computer,however, there may be a shortcutthat can take you directly fromyour sketch to a reliable, working

This is an adaptation of an article by Falk, afree-lance writer and former electronicsmagazine editor who has published severalbooks and articles about using personalcomputers.

circuit. With inexpensive circuitdesign software, you can type indescriptions of the componentsyou are using and the way they areconnected to one another. Thesoftware will then calculate theperformance you can expect fromyour circuit. If it does not meet ex-pectations, you can do additionalcomputer runs, changing compo-nent values until you get the de-sired results.

You don't have to write any com-puter programs to get these re-sults. What you must do is learn touse one of the commercial comput-er -design software packages thatare currently available. That will

Figure 1. This ratio multiplier circuit, simulated by the ACIRC package, has 16 nodes(see circled numbers). Each of the input code lines that describe the circuit forACIRC contains information on node connections and operating parameters for oneof the components.

take some time and effort, but it iswell within the grasp of anyonewho can put together a workingelectronic circuit.

Simulated circuitsIf you think software packages

that sell at reasonable prices haveonly trivial capabilities, thinkagain. These packages typicallycan handle circuits with 30, 40 ormore nodes. (A node is simply aconnection point for two or morecomponents.)

Take a look at the 16 -node ratiomultiplier circuit shown in Figure1. It includes eight transistors, twodiodes and an operational ampli-fier. A program with a 30 -nodecapacity can handle circuits ap-proximately twice as complex asthis one.

The calculated results thesepackages will produce include dccircuit parameters such as volt-ages, currents and power for allcomponents or for selected compo-nents. These results allow users todetermine immediately neededpower and voltage ratings for com-ponents, as well as power supplyrequirements.

Packages designed to simulateac performance go further. For in-stance, with ACIRC, offered byFB Circuit Products, the signal(sweep) input to the circuit beingsimulated can be specified by an in-itial and final frequency, an initialfrequency step, and a multiplierthat selects linear or logarithmicsweep. To excite the circuit with asingle frequency, the user simplysets the initial and final frequen-cies to the desired value. Thepackage then calculates resultssuch as voltages, phase angles andgains at nodes or across branches.


Don't expect instantaneousanswers from these circuit -designpackages. The computations theygo through are often very complexand lengthy. Results for a typical40 -node circuit calculated by theACAP package will take an IBMpersonal computer a full 40minutes to complete.

Components on tapCircuit -simulation packages

recognize and use only certaintypes of components. All thesimulation packages make avail-able passive components such asresistors, capacitors and induc-tors, and all allow use of voltage orcurrent sources, or both. TheACIRC package also provides foruse of transformers in circuits.

In addition to limits on thenumber of nodes a package willhandle, there may also be specificlimits on the number of eachspecific type of component thatcan be used. Users of the DCNAPsoftware package from BV Engi-neering are limited to no morethan 70 resistors, 30 inductors, 30capacitors, sources,independent current sources and30 dependent current sources. Thetotal of all components in a circuitsimulated by DCNAP must not ex-

ceed 200. The numbers differ forother packages, but most of themalso have their component limits.

With some of the packages, likeACAP (from DYNACOMP),DCNAP and ACNAP (from BVEngineering), users have to con-struct their own models of tran-sistors and other active devices us-ing combinations of the circuitelements the package recognizes.(See Figure 2.) The ACAP manualshows suggested models for op -amps. (See Figure 3.)

Other packages come with activedevice models that can be calledfrom storage and inserted into cir-cuits as components. For example,the DCIRC and ACIRC packages(both from Circuit Products) comewith simple models of transistors.FETs and op -amps.

The CircuitPro package (fromE/Z Cad) analyzes circuits with asmany as 120 to 150 transistors andcomes with ready -to -use modelsfor 48 industry -standard diodes, 35bipolar transistors and seven typesof operational amplifiers. Themodels are quite realistic. For ex-

the op -amp models includealmost all the first- and second -order characteristics found in real -world amplifiers. (See Figure 4.)

Users can also define their own

N2222

E

2N2907

LOW -FREQUENCY MODEL

B

HIGH -FREQUENCY MODEL

40 8.8pF

700

50kQ

Figure 2. Low- and high -frequency transistor models must be made up of com-ponents recognized by the ACNAP package.

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Figure 3. The manual for the ACAP package recommends this model for op -amps.Models such as these are created by the user. Here resistor and current -source com-ponents are calculated and specified by the user. The quantity A is the gain of theop -amp.

models for other devices and listthem as sub -circuits, which canthen be used, by name, as standardelements whenever needed. Mostelements also have model param-eters that can be used to define theshape of their characteristiccurves.

Checking worst -case scenariosAn important feature, offered by

many of the packages, is simula-tion of the kinds of variations thatcan be expected in components.When a circuit is built, componentvalues will be defined withintolerance ranges. A 5,00052resistor with a 20% tolerance mayactually have a resistanceanywhere between 4,00052 and6,00052.

The ACAP package takes a sim-ple approach. It calculates themean and standard deviation ofselected node voltages, based onthe component tolerances. Thesestatistical results give the usersome idea of the limits of perform-ance that can be expected due tocomponent variations.

Another approach is to allowusers to simulate the changes inoutput that will result from a smallchange in the value of a compo-nent. The ACNAP package usesthis kind of sensitivity analysis toreveal the amount by which themagnitude and phase of the outputwill be affected by a 1% change inthe value of any component.ACNAP also has a Monte Carloanalysis feature that randomlyvaries component values withintheir specified tolerances. Resultsindicate the statistical limits of thecircuit responses.

Such calculations can be ex-tremely valuable, particularlywhen many copies of a circuit willbe fabricated. However, usersmust be prepared to wait patientlywhile the software threads its waythrough the computational com-plexities. DCNAP, which has sen-sitivity and worst -case analysiscapabilities similar to those ofACNAP, ran a typical sensitivityanalysis for a 4 -node circuit in 107seconds. A worst -case analysis forthe same circuit took 81 seconds.Obviously, run times for analysesof larger circuits will be muchlonger. With ACAP, it may take10 or more iterations of thestatistical calculations to get ac-curate results.

Extras and errorsSome of the packages have im-

portant extra features. For exam-ple, the ACNAP package uses thedesired frequency range and thenumber of integration steps tocalculate the noise equivalentbandwidth. (See Figure 5.)ACNAP can also produce a filethat allows computation of the cir-cuit's time -domain response, al-though the file has to be processedby a separate signal processingpackage from the vendor.

The DCIRC package caters tousers who want to accurately fine-tune output based on componentparameters. (See Figure 6.) Theuser adjusts the parameters, thengets a rapid display of outputresults on which to base furtheradjustments.

Users will inevitably make er-rors as they try to get thesepackages to solve circuit -design


SECOND -ORDER BANDPASS BIQUAD

OP AMP MACRO MODEL

.SUBCKT AMP 1 2 3 4

GAMP 3 4 1 2 1KROUT 3 4 100CPOLE 3 4 16UENDS

BIQUAD

R1 1 2 1.6KR2 2 3 1.6KC2 2 3 0.1µFR3 2 4 160R4 3 5 160R5 5 6 160R6 6 7 160C6 7 4 0.114F

XOA1 2 0 3 0 AMPXOA2 5 0 6 0 AMPX0A3 7 0 4 0 AMP

INPUT SOURCE

VIN 1 0 AC 1

CONTROL STATEMENTS

.AC LIN 100 5K 25K.PLOT AC VDB (6) VP (6).PRINT AC VDB (6) VP (6).END

Figure 4. Input statements to describeand simulate a bandpass filter circuitwith the CircuitPro package are shownabove. At the top right is an "op -ampmacro model" that is used three times inthis circuit. The circuit itself, with nodenumbers circled, is shown at the rightcenter. At the bottom right is the outputfor gain and phase from 7,000Hz to13,000Hz, as plotted by CircuitPro.

problems. Unfortunately, most ofthe packages do not provide con-venient ways to handle and correctsuch errors. Some provide no errormessages at all; others, likeDCNAP, make some effort to doso. DCNAP is designed to recog-nize certain errors, such as num-bers, components or nodes thatare called for but do not exist inthe circuit description. If the usermakes one of these errors, thepackage will display the warning"ILLEGAL ENTRY, please tryagain." When other errors such asrunning out of disk storage spaceoccur, the package is not so le-nient, and the user has to start allover from the beginning of the pro-gram sequence.

In ACNAP, error messages are2 -digit numbers; the user refers toa list in the manual to interpret

VIN

OOP -AMP MACRO MODEL

R1

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FREQUENCY (x10,Hz)F;,=10kHz:0=10;0=1

them. In some cases the packagesimply refuses incorrect input andreturns the user to the previousprogram step. However, the ven-dor promises to clear up, over thephone, any error situations theuser cannot understand.

Finding the right packageMost of the effort a user will put

into one of these circuit simulationpackages will be in the form ofkeyboarding circuit descriptions.In the long run, packages withconvenient data input facilities arethe ones that will be easiest to use.

Input data may be entered oneline at a time or may be in the formof an entire input file that usersprepare with their own editing orword processing software. Ineither case, users will have to learnthe exact formats that are to be

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Figure 5. This bode plot for a bandpass amplifier, produced by the ACNAP package,shows the magnitude and phase response of the circuit over a defined frequencyrange.

Figure 6. This voltage regulator circuit, laid out for simulation by the DCNAPpackage, uses the two dependent current sources, R2, V2, R3, V3 and the 120Q and104 resistors to model two transistors. Nodes are shown as circled numbers. Forthis package, the ground node is always numbered O.

used, including the order and man-ner in which component names,types, node -connections and otheritems have to be entered.

If the data is keyed in wrong orthe circuits need to be revised, theinput may have to be changed,sometimes while it is beingentered, often after a complete setof data has been entered. In anycase, the data will have to beedited, so the facilities provided bythe simulation package for suchediting are important.

More or lessMost of the packages in the ac-

companying sidebar are roughlyequivalent in price and capabili-ties. CircuitPro is an exception. Itis considerably more expensivethan the other packages and ismore powerful. At the same timeits price, about $1,000, is wellunder that of the very sophisti-cated circuit simulation softwarepackages used by professional in-tegrated circuit designers.

Most of the packages can handlefive basic circuit elements(resistors, capacitors, inductors,voltage and current sources); ac-tive devices often must be modeledwith combinations of those basicelements. Other packages alsohandle active devices.

At the other extreme are theEE1 and EE2 packages. These dono circuit simulation at all. Insteadthey provide a selection ofspecialized calculations that can beuseful in circuit design. The EE1includes 17 different calculationsfor do circuits, of which seven haveto do with charge and discharge inRC or RL component combina-tions. The package does not go sofar as to deal with RLC combina-tions. There is also a table thatdisplays resistances and fusingcurrents for various gages of cop-per wire.

The EE2 package (for ac cir-cuits) offers similar facilities.Here the calculations include suchassorted items as complex numberarithmetic and calculations fortwin -t filters, skin effect, radiationfrom a wire pair, bandwidth -risetime and transformers. The wiretable is also included in thispackage.

ASeitv44 Electronic Servicing & Technology December 1987

Circuit -design softwareACAPLimit: 40 nodesCircuit elements: basic five plus conductance, voltage -controlled current

sourcesActive devices: user -modeledFunctions: node voltages, mean and standard deviation of node voltages,

output frequencies, radian frequencies, output in decibelsPC type: IBM/PCs, most other typesPrice: under $50Vendor: DYNACOMP, 1064 Gravel Road, Webster. NY 14580;

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ACIRCLimit: 40 nodesCircuit elements: basic fiveActive devices: transistors, FETs and op -ampsFunctions: phase angles, voltages and gains at nodePC type: IBM/PCs and compatibles with 192K main memoryPrice: about $100 (includes DCIRC package)Vendor: FB Circuit Products. 5234 Longfellow Way, Oxnard, CA 93003;

805-986-2276

ACNAPLimit: 30 nodesCircuit elements: R, L and C components, dependent current sourcesActive devices: user -modeledFunctions: node magnitude and phase response, sensitivity analysis,

Monte Carlo analysis, noise equivalent bandwidth, time -domainresponse (signal processing package required)

PC type: IBM/PCs and most other types; PC- or MS-DOS requires 256Kmain memory; CP/M-80 requires 62K; TRS-DOS requires 48K

Price: under $100Vendor: BV Engineering, 2200 Business Way, #207, Riverside, CA 92501;

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CircuitProCircuit elements: 15 (basic five plus diodes, voltage -controlled current

and voltage sources, current -controlled current and voltage sources,junction FETs, mutual inductors, inductors, MOSFETs, BJTs,transmission lines, independent voltage sources)

Functions: frequency response, time response, sensitivity analysisPC type: IBM/PC/XT/ATs (PC version of the UC Berkeley Spice simulator)Price: about $1,000Vendor: E/Z CAD, 5589 Starcrest Drive, San Jose, CA 95123

DCIRCLimit: 40 nodesCircuit elements: resistors (50), voltage sources (10), current sources (10),

diodes (10)Active devices: stored models for transistors (25), FETs (10) and

op -amps (10)Functions: Voltage, current and power for components; node voltages;

input and output resistance; sensitivity analysisPC type: IBM/PCs and compatibles with 192K main memoryPrice: about $100 (includes ACIRC package)Vendor: FB Circuit Products, 5234 Longfellow Way, Oxnard, CA 93003;

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DCNAPLimit: 30 nodes, 200 componentsCircuit elements: basic five, plus dependent current sourcesActive devices: user modeledFunctions: node voltages; current, voltage and power for circuit

branches; sensitivity analysis; worst -case analysisPC type: IBM/PCs and most others (memory limitations are the same as

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Tracking down

remote control

proi4lem

By Conrad Persson

The infrared remote control is acommonly used accessory for con-sumer electronics products. Thesedevices are convenient andreliable, but occasionally they dobreak down. Here are a few pro-cedures to follow if you encounter

remote -control products thatmalfunction. Because these sug-gestions were adapted from RCAservicing information, they arespecific to RCA products, but themethods can be generalized tosome degree to suggest ap-

UP/DOWN PRE -AMPCHANNEL MCY003VOLUME PW900SWITCH r-- - r

TRANSMITTERCAK 26

CHASSISREMOTEPROGRAM TIME SET DECODER AC ON/OFFSWITCH SWITCH

REMOTE RECEIVER(ADO) (HOURS)(ERASE) (MIN) MCR007 OR MCR01? CHASSIS(SEULOCK) VIDEOPwn00 i

TO TVCHASSIS

J

P W?500 DISPLAY 'CLOCKDRIVER PW2400 AU3

N

MEMORY

Ud

FREOSYNTH

U1

OP AMPSWITCH

U? o

PRESCALERU1 B

L

OMSC003B

0MS T003A C

I(CONTROL MODULE TUNER MODULE

IF/AGC

proaches to other product lines.

How the remote system worksThe FS Scan Remote system

(see the block diagram in Figure 1)

Persson is editor of ES&T.

VERT BLANKING

60V P.P

TO LOW.LEVEL VIDEOSTAGES

TO PI ON

HIGHATED PULSESINDICATE TIME/CHANINFORMATION

MST 001 MODULE

SEE "DC TUNINGVOLTAGE ANO PRE -SCALER FREQUENCYCHART FOR MST 001TUNER."

SEE "BANDSWITCHINGCHART FOR MST 001TUNER" FOR PROPERBANDS WITCHINGVOLTAGES.

GND

PRESCALER

- UHF5.1V

T.V.- V.N.

CHANNEL DIRECTIONCONTROL PUSH -BUTTONSAND/OR REMOTE COMMAND

UP OR DOWN LINEGOES TO LOGIC "LOW"WHEN APPROPRIATEBUTTON IS ACTIVATED.

VTO REMOTE RECEIVERMCR 003

+ 10V-.IMIX I+)

Figure 1. Block diagram of the remote tuning system.


uses a frequency synthesizer chip,an op -amp chip, a memory chipand an on -screen channel -display/clock chip. These ICs andassociated components make upthe MSC 003 tuner controlmodule. (Figure 2 shows the PCboard layout for the scan remotesystem.) This discussion will focuson the display/clock interface andremote servicing procedures. (Forfurther information on how in-frared remote controls operate,see "What Do You Know AboutElectronics?" in the April and May1987 issues, titled "InfraredRemote Controls" and "More onthe Basics of Infrared RemoteControls," respectively.)

The scan remote system includesthe MCR 003 remote receiver,which uses a remote decoder IC.(Figure 3 shows the pin -outdiagram.) This IC processes chan-nel up/down, instrument on/off,and volume up/down informationfrom the remote -control unit via apre -amp and then sends ap-propriate voltages to the controlmodule. The remote receiver alsoprocesses function commandsfrom the manual push-buttonassembly located on the television.

Also located on the remotereceiver is a + 11Vdc regulatorthat provides do voltages to theremote receiver and pre -ampboard (as long as the television isconnected to the ac line).

A separate transformer providesac power to the regulator forstandby and operation voltages tothe remote receiver and pre -amp.A relay provides on/off power tothe TV receiver.

Symptoms associated withremote control

Symptoms of problems with thetime -setting mechanism include: Inability to set time. Erratic display. Loss of time display.

Symptoms of problems with thechannel selector include: No channel up/down - remote. No channel up/down - manual

buttons. No channel up/down - remote or

manual.

Symptoms of problems with thevolume control include: No volume up/down with remote

and/or manual buttons.

STANDBY VOLTAGE

THIS VOLTAGE DERIVEDFROM MCR 003 REMOTERECEIVER

FROM REMOTERECEIVER

IAA) 11 3V DCIS/

GND

J,1,

DISPLAY CLOCKREFERENCE 60H,

GOES TO LOGIC"LOW" WHEN IHRSIOR (MINI BUTTONACTIVATED

MIN HRS

FI IEI

W,Y 111W.r,

s / ``\(1\- \.s ..

é ' \i ` P1 T : e mENCY \lSlzlw-li'

ADO (TI

ERASE IUIJ

SELECT/LOCK (VI -

(WI

WHEN EITHER A00 1 I

OR ERASE I -I BUTTONIS ACTIVATED. APPROPRIATE POINT SHOULDGO TO LOGIC LOW"STATE

LOGIC "LOW` INSELECT AND LOCK

-60V PULSES

VOL/MUTE -60V PULSE -

GND

-- . I9V ITP II -

AFT IN

VOL/MUTE LINELOGIC -LOWDURING SCAN

DC VOLTAGE SHOULDINCREASE AS VOL/UPIS ACTIVATED ANDDECREASE WHENVOL/ON IS ACTIVATED

VOLUME CONTROLDERIVED FROMMCR 003

TO TV

CHASSIS

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Circle (33) on Reply CardDecember 1987 Electronic Servicing & Technology 47

~+

3. CONFIRM 3.57-MHZCLOCK SIGNAL

J)

IC 491-~Y AMP/DET

e

PD 497 a

+5V

iCN490-1 0401

R406

1 CONFIRM PRESENCEOF SIGNAL FROMHAND TRANSMITTER

-5V - 0402RESET

4. CONFIRMRESET "Hi"

ZO 401 (5V 2 CONFIRM 5 -VOLT

SUPPLY

3.57 MHz

Hil

IC 401RC pP

omo

ñJ

_= J= CHANNEL

LOCh(REC)

11

0405

1TO 26 PINCONNECTIONSERIALI6 -BIT CODE

5 -BIT

4 -BIT

REMOTE POOE/

SLOWTRACKING

o

CHANNESELECT

I{

CHANNELUP

CHANNELDOWN

TV VCRSELECT

TOPLL r

Figure 3. Pin -out diagram of the remote -control decoder IC.

Improper volume up/down withremote and/or manual buttons.

Other possible symptoms: No remote -control action.

No on/off action from eitherremote or manual buttons.

Servicing proceduresUse an isolation transformer,

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The method mostmanufacturers

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disconnect the line cord during allstatic checks, and use insulatedclipleads for dynamic checks.

As a precaution, check all inter-face connections and wiring to andfrom the remote control module,the remote receiver, the pre -ampand all other assemblies associatedwith this system.

Display problemsSymptom: You are unable to set thetime, the display is erratic or hasbeen lost altogether.

Display problems can be definedas erratic or distorted screen digitdisplay or no display with other-wise normal operation. Such prob-lems are usually confined to theclock and display IC, located onthe control module, or to connec-tor problems. If you encounterdisplay problems, replace the con-trol module. A defective displayassembly also may cause videoproblems. If you suspect that videoproblems are caused by the displaysystem, remove the connector tosee if the problem clears.

Learnhow to repairVCRs...

ReadVideo Corner

each monthin GIGOTRODIC

Servicing &Technology



Failure of the system to main-tain the correct time of day is acomparatively improbable situa-tion without other symptoms beingevident. If you encounter this:1. Check for possible intermittentpower interruptions. If power tothe TV set is interrupted, the time -of -day display will be lost whenpower is restored, and the clockwill have to be reset.2. Check the time -set switches andcabling for possible intermittents.

Channel -changing problemsSymptom: No channel up/down-remote.

Confirm good connections be-tween the remote receiver and thepre -amp. Monitor logic conditionsat pins 9 and 11 of the remotedecoder on the remote receivermodule. This should go low when achannel button is depressed. If thelogic condition does not change,the problem may be a defectivecomponent on the remote receiverboard. Confirm the presence of+ 11Vdc to the remote decoder ICand to the pre -amp board.

Symptom: No channel up/down-manual buttons.

If the remote receiver respondsto remote channel up/down, checkconnections between the remotereceiver and the manual buttonassembly.

Symptom: No channel up/down-remote or manual.

Check logic conditions at X andY on the control module (seeFigure 2). If proper logic condi-tions are available on the controlmodule but the correct commandfunction doesn't occur, replace thecontrol module.

Volume problemsSymptom: Improper volume up/down or no volume control-remote.

Confirm good connections of theremote receiver and pre -amp. Ifconnections check out, replace theremote receiver.

Symptom: Improper volume up/down or loss of volume control -manual buttons.

Confirm good connections be-tween the manual button assemblyand the remote receiver. If the

problem persists, replace theremote receiver.

Symptom: Improper volume up/down or loss of volume control inremote or manual operation.

This usually indicates a problemassociated with the remote decod-er IC or within the TV sound sec-tion. First monitor the do voltageat point W on the remote controlmodule (see Figure 2). Press thevolume up/down buttons and con-

firm that de voltage tracks whenthe appropriate button is pressed.If the voltage does not change, re-place the control module.

Other remote control problemsSymptom: No remote -control ac-tion (manual OK).

A problem such as this usuallyindicates a defect in the remotetransmitter, the pre -amp or the re-mote receiver. Check the transmitter battery.

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Confirm correct function com-mand frequencies of the trans-mitter by using a frequencycounter at the remote receiver.

Confirm that + 11Vdc is presentat the remote receiver. If man-ual tuning operates properly,the remote decoder IC is receiv-ing + 11V. A good place to con-firm + 11V is at point AA on theMSC module (see Figure 2).

Try a substitute module.

Symptom: No on/off action fromeither remote or manual controls.

On/off problems are usually con-fined to defects on the remotemodule; ac power for the televisionis via a switching relay circuit alsolocated on the module.

When you press thepower button, listen fora click from the re-lay. A click will indicatewhether the dc controlvoltage is getting to thecontrol winding, and will suggestthat the remote receiver is op-erating property.

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Remote control unitscomplicate servicing pro-cedures by adding more

elements that may have to bechecked, but with a little bit of luckyou can determine whether a prob-lem is related to that circuitry.

Whenever a remote controldoesn't work or operates erratical -

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ly, start by replacing the batterywith the recommended replace-ment. If that doesn't solve theproblem, you can make a prelimi-nary check of the remote unit byaiming it at a special card that issensitive to infrared light. If thetarget on the card lights with aflickering light when you press anyof the control buttons, you haveconfirmed that it is operating.

The next step is to substitute aknown -good remote unit for the in-operative one. Make sure there isnothing covering the infraredreceiver on the set. If thesubstitute remote control operatesthe set, you have isolated the prob-lem to the remote control.

Troubleshooting the remote-

control function of a consumerelectronic product is a lot liketroubleshooting any other aspectof the unit: Understand theoperation of the circuits, isolatethe cause of the problem throughchecks and substitutions, andrepair or replace the defectivesegments.

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This in-depth discussion of pow-er regulation problems and solu-tions for mini, mainframe and mi-crocomputers addresses powerregulation and how to use theproper electrical power. Topicscovered include: utility power,grounding, lightning, static, noiseand transients and their effects onpersonal computers and officeelectronics. The book also discuss-es isolation, distribution and volt-age regulation, and covers the dif-ferent types of power conditioningequipment.Published by Howard W. Sams & Company,4300 W. 62nd St., Indianapolis, IN 46268;800-428-SAMS.

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This ready -reference manualcontains up-to-date technical data,terminology and "how it works" in-formation in a combination dic-tionary/encyclopedia format. Thebook contains a list of alphabetical-ly arranged electronic terms, de-tailed illustrations, charts, tables,schematics, formulas, graphic sym-bols and conversion factors. Thereis also an expanded encyclopedictreatment of the main branches ofelectronics, including transistorcircuits, optical communications,computers, microelectronics andnuclear physics.Published by Prentice -Hall, Englewood Cliffs,NJ 07632; 800-223-1360.

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EIECTNOAiCPractical techniques for todays servicing professional


What doyou know aboutelectronics?

By Sam Wilson, CET

In the last issue we borrowed thespace ship from "FantasticVoyage" and took a trip into asmall block of germanium. Stop-ping just inside the surface, we ob-served Brownian motion and in-trinsic current. We will now makea return trip to observe some newsights.

Our lab assistants are told toplace a very small opaque dotbehind us after our space shipenters the block of germanium.Special lab equipment is neededbecause we have been reduced to asize that is invisible to the humaneye.

Just inside the surface we stopand wait. When the black dot is inplace we signal the lab assistantsto shine a very bright light on thesurface. The light penetrates thesurface and bathes the atom in aneerie glow.

Huge objects that look likeboulders come crashing into thematerial from behind. They arephotons - that is, particles oflight.

We are protected from thesephotons because they cannot passthrough the black dot that wasplaced behind us. The high-speed

Wilson Is the ES&T electronics theory consul-tant.

A trip to thedeathnium traps

boulders crash into the atoms ofgermanium and knock electronsloose. This greatly increases theintrinsic current that we noted inour previous journey.

At our signal the bright light isturned off and we move into thecrystalline structure. It isnecessary to provide our own lightfor this part of the journey.

We are still fascinated by thebeautiful and orderly structure ofatoms. Our space ship pulls along-side a place where a larger atomhas been wedged into the crystal.It obviously does not belong therebecause it does not fit into the lat-tice structure.

This out -of -place atom is thrash-ing about, but it is firmly stuck.We are told by the guide that it iscalled an interstitial atom. It is, infact, an atom of copper that hassomehow become trapped betweenthe atoms of germanium.

A passenger asks why electronsare landing on and taking off fromthis atom. We are told that thecopper atom is a form of death-nium trap. It captures electronsmomentarily, disrupting the flowof charge carriers through thematerial. If there are too manydeathnium traps, the material isworthless for use in diodes andtransistors.

We are reminded that the thingswe see on the trip through ger-manium are identical to what wewould have seen if we had enteredsilicon.

At out next stop we observe inthe lattice structure an atom thatis slightly larger than the otheratoms. An electron is circling itlike a tiny moon. This is a donoratom used to make the block ofgermanium N -type. If an externalvoltage is applied, the circling elec-tron can easily be pulled awayfrom its atom.

While the circling electron isloosely attached to its atom, thereis no unbalanced charge. Itbelongs there and it is both elec-trically and gravitationally at-tracted to its atom.

So, the N -type material is notnegatively charged. (Nor is theP -type material positivelycharged.) A better name couldhave been chosen for thesematerials so as to avoid the mis-taken idea that they are negativelyor positively charged.

Our ship makes a wide 180° turnso we can emerge from the sameside as we entered. However, ourpath is soon blocked by what ap-pears to be a wall. All of the atomsalong the surface of this wall havefallen out of place so that the lat-


tice structure is no longer intact.It is another kind of deathnium

trap. This one is called a grainboundary. We are told that thisdeathnium trap will make the ger-manium useless for semiconductorwork.

You can see one or more grainboundaries in an ice cube. Theylook like an internal crack.However, if you turn the ice cubeand try to look at the grain bound-ary on edge it will disappear.

We contact the lab assistants forhelp. Their computer plots a patharound the grain boundary and weleave the surface of the cube. Aswe are being returned to full sizewe are told that we would surelyhave been stuck if we had tried topass through the grain boundary. Idecide against any future trips. I'mno hero.

The programmableShockley diode

In a recent issue I noted thesimilarity between the model usedfor a Shockley diode and the oneused for a 4 -layer (Shockley) diode.(See Figure 1.) I had heard fromsome source - which I can'tremember-that an SCR can beused as a Shockley diode if thegate is left open.

Two students at New EnglandInstitute of Technology in WestPalm Beach, FL, decided to try itand got some astonishing results.

When Randall Wolf and GlenLangley tried to make an SCR into

iANODE

P

N

GATE P

N

CATHODE

FIGURE 1

1 ANODE

P

N

P

N

iCATHODE

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a 4 -layer diode, they found theydidn't have enough voltage tomake the device break over in theforward direction. So they decidedto lower the forward breakovervoltage by applying a slightlypositive potential to the SCR gate.

Figure 2 shows the circuit theyused. Their reasoning was that ifthe device did break over, it shouldproduce oscillations. The arrowson the schematic show the chargeand discharge path for theresulting relaxation oscillator.

The device did break over andoscillation occurred. More impor-tant, the frequency could bechanged. Therefore, changing thegate voltage changes the forwardbreakover voltage. That makes it aprogrammable 4 -layer diode.

The students have applied for apatent disclosure letter. Figure 3shows their suggested symbol.

I, for one, never cease to beamazed at the innovative ability ofstudents!

The slide -back meterI had a chance to talk with my

friend Earl Tickler at the recentNESDA/ISCET/TESDA conven-tion in Memphis, TN. His studentsat RETS (in Baltimore) requestedthat I discuss the slide -backvoltmeter in my article. It wasmentioned in a previous "TestYour Electronics Knowledge."

The slide -back meter is usedprimarily to measure the peakvoltage of a sine wave. The basiccircuit is shown in Figure 4.

When there is no ac voltage ap-plied, the sensitive meter readszero current. Actually, a verysmall amount of leakage currentmay flow, especially if the probesare not isolated from each other.

When the ac voltage (to bemeasured) is applied, it is 1/2 -waverectified by the diode. The arm ofR is adjusted until the currentmeter reads just a hair above zero.

In other words, the cathode ofthe diode is made positive enoughthat it will not conduct. The reasonyou want a very slight indicationon the current meter is to makesure you are just at the peak pointof the ac voltage input.

At that point the voltmeter in-dicates the peak value of theunknown voltage.


The question asked by otherslistening to our conversation was:"Why bother? You can do the samejob with any modern oscilloscope."There were several replies that areworth considering. You wouldn't know whether you

liked the idea if you didn't knowwhat it was.

It is cheap. Some young experi-menters haven't obtained anoscilloscope yet, so this givesthem a way to measure the peakvoltage.

It is important to periodically re-view some of these older tech-niques. There may be an applica-tion in modern technology.

Stick -on meterNo, this isn't another meter cir-

cuit. Don Turner, CET, of WestPalm Beach, FL, sent this tip.

When making measurements inthe field, he got tired of trying tofind a place to put his VOM, so heattached a suction cup to the backof the meter. He used epoxy, buthe said that a small screw couldalso be used.

Whenever he makes measure-ments, he just sticks the meter on-to a nearly flat, smooth surface.

If any other reader has afavorite technique, please send italong.

A letter from Raymond McCoyDear Sam:

At the end of your "What DoYou Know About Electronics,"page 46 of the May 1987 issue, youquoted a college professor asstating, "A battery cannot producevoltage at any time unless currentis being drawn from that battery."

In my opinion, a battery isalways drawing current. A betterway to phrase the statement is:"A battery is always producingvoltage because current is alwaysbeing drawn due to its dischargecurrent (no matter how minute).This discharge current is createdbecause NO insulator is perfect."

Thanks for the letter, RaymondMcCoy. I found your comments onthe battery interesting. Accordingto your idea of the imperfect in-sulator, it could very well be im-possible to prove that current isnot required for producing a bat-tery voltage. On,

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Industrial soldering ironsO.K. Industries has introduced

the SA -8 industrial -power solder-ing iron series. The ergonomicallydesigned irons have a 3 -wiregrounded power cord and a maxi-mum equivalent rating of 30W,40W and 50W.

Features include: accuratetemperature stability, whichprevents damage to boards andcomponents; quick heat -up timewith rapid temperature recovery;silicone rubber heat guard foroperator comfort and a safe,positive a long -life, corrosionresistant tip; and a grounded tipfor CMOS-safe soldering.


Parallel -to -serial converterThe model 232 PSC parallel -to -

serial converter from B&B Elec-tronics gives users the conven-ience of another PC serial port.The male DB25P connector inputsparallel data using the standardPC pinout. The RS -232 serial datais output on pin 3 (RD) of thefemale DB25S connector. Thisport is configured DCE for directconnection to most serial printers.The pins 4 (RTS) and 20 (DTR) areRS -232 inputs used to stop thecomputer from outputting datawhen the printer is busy. The con-verter comes with an ac powersupply and may also be pro-grammed for 150 baud to 9,600baud, parity, 7 or 8 bits, number ofstop bits and busy input on pin 4 orpin 20.


Tool kitA 26 -piece tool kit in a fold -up

plastic case is available fromXcelite. The kit, model 99SMWX,contains a soldering iron and tip, a

wire stripper, nine nutdrivers,Phillips and slotted screwdrivers,a wrench, a reamer, an extensionbar for the nutdrivers and screw-drivers, and two screwdriverhandles.


Monitor cleanerChemtronics has introduced

Screen Prep, a 2 -part screen -cleaning system that consists oftwo disposable cloth pads sealed intwin foil packets. The first packetcontains a wet pad, premoistenedwith a cleaning solution thatremoves dirt, fingerprint oils anddust and also controls screenstatic. The second packet containsa soft, lint -free pad for drying thescreen.


A/V soldering courseHexacon Electric Company is of-

fering a slide and audiocassettetraining program for entry-levelpersonnel who will be performingwiring and hand soldering. Theprogram describes the techniquesrequired for correctly solderingturret, bifurcated, hook and cupterminals, and shows how a goodsolder joint should look.


Cleaner/burnisherThe Superbrush cleaner and bur-

nisher kit from the Eraser Com-pany contains a holder with threeinterchangeable refills (coarse andfine fiberglass and stainless steel).Each refill gives a different clean-ing action, ranging from a finepolish to a coarse sandpaper finish.

The kit may be used to cleanelectrical contacts, deburr smallmetal parts, remove rust fromtools, clean motor commutators,polish molds or clean printed cir-cuit boards.


Power control unitDATA SPEC has introduced the

PC1025 multifunctional controlunit, part of the Director Series.The unit incorporates surge sup-pression, an A/B data switch, adigital LED clock and individualswitching capabilities for up to fivecomponents.

Five front -mounted on/offswitches for the computer, printer,monitor and two auxiliaries pro-vide power to specific componentsas needed, and a master switchpowers up the entire system.


CleanerThe MCC-DFX Genesolv solvent

from Micro Care Chemical Cor-poration cleans without the use ofchemical additives that presentsafety hazards. The non-flammable fluorocarbon solventremoves organic and ionic con-taminate residues associated withall commercial rosin -based fluxesand solder pastes.

The cleaner can be sprayed di-rectly from the can or it can be ap-plied with the Trigger Grip remoteapplicator, which dispenses thesolvent through a natural bristlebrush.


Oscilloscope with cursorsLeader Instruments has intro-

duced the model LBO -2060 60MHzCRT readout oscilloscope with cur-sors, which allows the user toobserve waveforms, setting condi-tions and measured values on asingle display. The scope reducessetup time by displaying thesalient setting conditions such asCH -1 and CH -2 sensitivity, mainand delayed sweep time and trig-gering controls.


Soldering/desoldering stationThe Twin E999 electronic,

temperature -controlled soldering/desoldering station from ELVO


has an operating range of 392°F to878°F. A Nichrome element wireprovides 45s heat -up and instantrecovery. Electronic OV thyristor

switching protects sensitive com-ponents. The tip is grounded to en-sure a voltage leakage of less than1mV and has a temperature sta-bility better than + 10°F. Otherfeatures are automatic solderingtip cleaning; a dual -diaphragm, oil-

free vacuum pump that provides23 -inch to 28 -inch Hg of vacuumfor desoldering; and a transparenthandpiece for monitoring soldercollection.


Tool kitJensen Tools has introduced the

Deluxe Tech School Kit #23B002,a tool kit for the advanced elec-tronics student and skilled hobby-ist. The kit includes 28 tools, in-cluding screwdrivers, nutdrivers,a wire stripper/cutter, pliers, scis-sors, wrenches, a hemostat, a mir-ror, holding tweezers and solder-ing equipment.


Analog multimeterA. W. Sperry Instruments had in-

troduced the SP -5 pocket-size ana-log multimeter. The 4 -functionunit has 12 ranges, recessed test-

lead connections and diode -pro-tected meter movement. Rangesare 10/50/250/500Vdc; 10/50/250/500Vac; 0.5/50/250mAdc; 0-1M(l(5k1Z mid -scale); and - 20dB to+ 56dB.


Torque gaugeTentel has introduced the

TQ-600 dial torque gauge, designedspecifically for video VHS andBeta recorders. The gauge is cali-brated in both clockwise and coun-terclockwise torque to 600g/cm formaximum accuracy.

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Lost the profitable extra $35 or more that you could have gotten forrestoring a CRT while on the job and locked in the profitable CRT sale later?

Avoided handling profitable trade-ins or rentals because you wereafraid you'd have to replace the picture tube when you could have restoredit?

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Computer Corner By Bert Huneault

RMMs: Erasable andThis is the third part in a 4 -part series on non-volatilememories. Part one covered the basic read-only memory(ROM). Part two discussed programmable read-only mem-ory (PROM), which is custom programmed by the user butcannot be erased and reprogrammed, and EPROMs, whichcan be reprogrammed.

Although EPROMs can be reprogrammed as often asnecessary, making them less expensive to program andmore practical for users who do not need a large batch of aparticular program, EPROMs do have some drawbacks.First, EPROMs must be removed from their sockets to beerased and reprogrammed. They also take a long time toerase, and the UV erase operation erases all memory con-tents simultaneously, necessitating complete reprogram-ming even when only one byte (memory word) needs to bechanged.

A different class of non-volatile memory is the electrical-ly erasable and programmable ROM, which was developedas an improvement to the EPROM. This type of memory isgenerally used in applications where it is frequently (most-ly) read, but may occasionally (seldom) be written to; thusit can be called a read mostly memory (RMM). This cate-gory includes two nearly similar types: the electrically al-terable read-only memory (EAROM), and the electricallyerasable programmable read-only memory (EEPROM, al-so abbreviated E2PROM).

How they workEAROMs use metal -nitride -oxide -semiconductor

(MNOS) technology; EEPROMs generally feature n -chan-nel, floating -gate technology, as does the EPROM. Al-though their gate structures are somewhat different, theyare both electrically programmable and electrically eras-able. They behave much the same way -a sufficiently highvoltage applied to any of the memory cells causes theRMM to store a charge in the selected field-effect capaci-

Figure 1. The EEPROM is electrically erasable, not UVerasable as the EPROM is, and features single -bytereprogramming. The extra WE (active -low write enable) con-trol pin allows more combinations of control -bus logic, whichgives the EEPROM more modes of operation.

Huneault is an electronics instructor at a community college in On-tario. Canada.

programmabletor. The charge is retained almost indefinitely (at least 10to 20 years).

But the charge can also be removed (neutralized) elec-trically with a voltage of opposite polarity to the MOSFETcell. Thus the EAROM and the EEPROM are both elec-trically erasable and programmable. Byte writing (writinga single word into the RMM) takes about 5ms to 10ms. Al-though too slow to be used as RAMs, these RMMs havetwo distinct advantages over EPROMs: They feature amuch faster erase speed (about 5ms to 10ms per byte), andthey allow the user to erase individual words in the mem-ory array without affecting the rest of the memory.Whole -chip erasure is also possible, and it too requiresabout 10ms.

ApplicationsAlthough EAROMs and EEPROMs have a limited life

span of 10,000 or 20,000 erase and programming cycles,they are ideally suited to applications where they store im-portant data for extended periods of time, such as taxtables in electronic cash registers, tab positions in CRTterminals, and tuning voltage codes in direct -access elec-tronic tuners for radios and TV sets.

In the latter application, the RMM stores a different bi-nary code for each of the VHF and UHF channel frequen-cies and also remembers the last channel viewed whenpower is turned off and back on again. When a channel isselected via the keyboard on the receiver's front -panel orhand-held remote -control unit, the corresponding memorycode is read from the RMM and is either converted into ananalog voltage (by means of a digital -to -analog converter)and applied to the tuner's varactors for channel selection,or it is processed by a microprocessor in a synthesized tun-ing system featuring a phase -locked loop (PLL).

No backup battery is needed to keep the data stored inthe RMM; once programmed, the EAROM (or EEPROM)retains the codes in its memory cells for more than a dec-ade, even when the TV receiver is turned off. If theset's owner moves to a different city where VHF/UHFchannel assignments are different or where local cable TVfeatures offset carrier assignments, the RMM can easilybe reprogrammed for the new frequencies via thereceiver's keyboard.

Note that unlike the EPROM, which must be removedfrom its socket for erasing and reprogramming, the RMMcan stay right where it is, in circuit; the support circuitrynecessary for erasing and programming operations is usu-ally incorporated in the PCB on which the EAROM orEEPROM is mounted, or aboard the memory chip itself insome of the newer RMMs.

Another application of EEPROMs is in state-of-the-artdigital displays on the instrument panels of modern auto-mobiles. In an electronic odometer, for example, the datais stored in semiconductor memory. Because the mileageinformation must be updated continuously, a RAM is usedto store the data. When the ignition is turned off or thebattery is removed from the car, however, the data mustnot be lost. In this type of system, a sensor detects the lossof power and causes the mileage data to be transferredquickly from the RAM into an EEPROM. The data remainsstored in the non-volatile EEPROM until power is re-stored, at which time the mileage information is returnedto the RAM for a resumption of continuous updating.


ANSWERSto the QUIZ

Continued from page 61. Doppler effect. The changein pitch of a train whistle as itapproaches and then leaves isthe most familiar example ofthis effect. The pitch is higheras the train approaches andlower as it leaves because thesound shares the velocity of thetrain.2. OV. The voltages at the op-posite ends of the transformershould be 180° out of phase, sothey should cancel. This test isused to determine if there areshorted turns on either half ofthe secondary. With shortedturns there will be an ac output.

i, iiau LIIC. mrprry v 7r.age, - oI = 10V/500(= 20mA.8. B. The voltage across R isequal to the rate of change ofvoltage across C.9. A. The input impedance of aMOSFET amplifier is high.10. e. Actually, it would be bet-ter to use the Greek letter ep-silon. This is a number that isoften associated with rate ofgrowth. If your calculator haslnx rather than e, the inverselnx of 1.0 gives the value of e.

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1. Quickly locate defective circuits by injecting signals without dis-connecting components.

2. Replace video heads with confidence; a simple good/bad head testremoves all doubt.

3. Align IF traps simply by just the pattern on the CRT - have thepicture "looking like it did when they bought it."

4. Quickly align VCRs with special video patterns, or NTSC color barsMeets all manufacturers' warranty requirements.

5. Performance test and troubleshoot any MTS stereo TV or VCRsystem, so you can cash in on new technology.

6. Confidently test deflection yokes, IHVTs, and flyback transformers,in -or out -of -circuit, before you replace them.

7. Add on phase -locked accessories into your video analyzing systemto increase service potential as technology changes.

8. Performance test and troubleshoot digital/analog RGB videomonitors, so you can test all of today's video systems.

9. Conquer tricky servo circuits in VCRs by injecting a reference30 Hz servo pulse.

10. Cut your video servicing time in half ... or your money back.

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Video Corner

Adjusting the tape transportif the picture produced by a VCR isn't all it should be,

the problem could be in the tape transport mechanism. It'simportant that the path between the supply reel and thetake-up reel is clean and stable. The tape transport is pre-cisely adjusted at the factory, but when parts related tothis section are replaced, it should be checked carefully

and any necessary adjustments should be made. The pro-cedures below, taken from the service manual for the GEmodel 1VCR2018W, give an idea of the kinds of checksand adjustments required to ensure that the tape trans-port in a VCR is operating properly.

Check item JudgmentBack -tension 30"45 gcm (VTR in horizontal)

Toollmeasuring instrument

Guide pole Tape should slide along the lower flange and notcrease or curl.

Back -tension meter

By eye

Inclined guide and Conspicuous creases or curls not present in tape. By eyeguide roller No adherence of dust.

Tape Conspicuous distortion of the tape or changeshould not be present.

Impedance roller

AC head

Envelope

Roller should rotate smoothly

Tape should keep contact fully with the controlhead core and audio head core.

AUDIO ERASE AUDIO CORE

HEAD

CONTROL 0 mmCORE

Playback Flatnessstaircasewave from Fluctuationalignmenttape

By eye

By eye

By eyeDiagram on the left showsreference values.

Conspicuous fluctuations should not be present AlignmentOscilloscope

The ratio of the max. section and minimumsection of the envelope should be 60% or more(with 1/2 output tracking position).

AlignmentOscilloscope

A/B 0.65Envelope wave

Adjust the positions shown below depending on the parts replaced when parts are refitted or replaced.

1. When the upper cylinder is replaced

Guide roller height

X valueSwitching pointVideo record levelVD (Dummy vertical sync)

JudgmentCreases and curls should not occur in the tapeCheck fluctuation and flatness of the envelopeCheck.

2. When the AC head is replaced

AC head heightAC head azimuthAC head tiltX value position

JudgmentCheck the audio or control track widthMaximize audio play5ack levelNo slack at the top and bottom of the tapeConspicuous audio level fluctuation should not be present


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ELECTRON CS

Industrial catalogBy writing on your company let-

terhead, or with any order, youmay receive a free 480 -page in-dustrial catalog from Joseph Elec-tronics. The catalog lists,describes and illustrates testequipment, tools and chemicals,wire/cable/connectors, batteriesand chargers, electronic com-ponents, computer accessories andvideo and sound equipment frommore than 100 national brands.

Another section features "valueadded services" stressing custombattery assembly.Contact Joseph Electronics, 8830'N.Milwaukee Ave., Niles, IL 60648;312-297-4200 (outside Illinois, call800-323-5925).

Test instrument catalogSencore Electronics has released

its 1987 fall/winter full -linecatalog. The catalog includes in-

struments for testing video, audio,components analyzers and cablesystems, plus waveform analyzers,IEEE instruments, and the com-plete line of instrument ac-cessories.


Technical supplies catalogContact East's latest catalog con-

tains a selection of test in-struments, soldering supplies,Contact East's exclusive line oftool kits, the latest in static protec-tion, wire cable tools, power sup-plies, electronic adhesives, dataand telecommunication equip-ment, and an extensive sectiondevoted to precision hand tools.


Precision tool folderMinitool is offering a folder

showing the company's line ofprecision miniature hand tools forlaboratory and production tasks,as well as for fine assembly work,delicate deburring jobs and printedcircuit artwork and repair. Shownare sets with hardened tool steeland carbide tips, technician sets,Tinitool kits, diamond scribers,

electrical micro -test probes withinterchangeable probe handles,micro -test probes with integratedhandles and audible beepers, preci-sion pin vises, sapphire burnisherand direct -reading micro -rulers.Also shown are micro -lapping kits,zirconium ceramic scissors andceramic tipped tweezers.


DMM brochureJohn Fluke Manufacturing Com-

pany is offering a new brochure,"A Test Lab in Your Toolbox - TheFluke 8060A." The 16 -page, colorbrochure describes how to use the8060A digital multimeter inseveral different industries. Manyworking environments are used toexplain procedures for currentmeasurements, calibrating processand control systems, and testingthe frequency measurement ofmotors and generators. Also in-cluded are tips for measuring theresponse of an equalizer, matchingresistors in step attenuators,measuring non -sinusoidal wave-forms and harmonics, plus othertesting methods. Q

Circle (128) on Reply Card esnw.-December 1987 Electronic Servicing & Technology 63

Audio servosIn past columns, I've talked about CD players and the

complex servos used to keep the micron -sized laser beamsfocused on the correct track. These circuits strain the lim-its of conventional home entertainment technology, asanyone who's ever been stuck with a balky CD playerknows. But what about the garden-variety servos in pho-nos and tape decks? We see these much more often.

To review, a servo is a device that uses its output to mod-ify its input, so as to keep some operational parameter,such as motor speed, constant. Take a look at Figure 1, asimple servo circuit with five essential components:1. a motor.2. a feedback circuit that has a signal, current or voltage

dependent on motor speed.3. a reference signal, current or voltage that sets the de-

sired operating point.4. a comparator that accepts inputs 2 and 3 and produces

a correction voltage in an attempt to equalize them.5. a drive amplifier controlled by the comparator.

Why bother with a servo at all? Why not simply use asynchronous motor and let the power company do the reg-ulation? Actually, that was common a few years back. Re-

Vistain is ES&Ts audio consultant.

REFERENCE

(FREQUENCYOR VOLTAGE)

FIGURE 1

COMPARATOR -. DRIVEAMPi

MOTOR

FEEDBACK (FREQUENCY OR VOLTAGE)

member Dual turntables with idler drive and large hys-teresis -synchronous motors? They ran almost perfectly insync with the ac -line frequency.

As good as it was for the times, line synchronization hadseveral drawbacks. First, the power -line frequency, whilehaving a long-term accuracy within an order of magnitudeof WWV, might vary a percent or two in the short term.Of course, if you used a line -operated strobe to checkspeed, you'd never notice it, because both the strobe andthe motor used the same reference.

Second, when this type of equipment was used in differ-ent countries, it required conversion of operating voltageand necessitated separate motor pulleys for 60Hz and50Hz systems. How many of you remember waiting weeksor months just to get a 60Hz pulley for a customer return-ing from a tour of duty overseas?

Not all countries control their line frequency as fastid-iously as the United States, so speed accuracy could not beguaranteed. Plus, a hysteresis synchronous motor alwaysevidences some slip or lag relative to the input waveform,and this slip becomes more severely detrimental to speedaccuracy with the varying loads typical in normal use of aturntable or tape deck.

Using de motorsTo get around these problems, producers of high-fidelity

equipment decided to go with do motors, which operatedindependently of the power -line frequency. As most of ushave noticed, the speed of small do motors is notoriouslyload -dependent. This wouldn't do, so early units used asimple voltage -regulator circuit. This wasn't a servo, be-cause no feedback was used. The regulator transistor wasthermally matched to the motor and was generally at-tached to the motor housing. Speed accuracy was within3%, with a wow and flutter specification around 0.07% to

FIGURE 2

SPEEDS101

SPEEDCALIBRATION

VR

SAW -TOOTHWAVE

SAMPLEHOLD

SCHMITTo 0 o 000

MIXMIX AMPFG AMP

VR101PITCH V V U

Q101

IC101

FG

HALLEFFECTSENSOR

///64 Electronic Servicing & Technology December 1987

By Kirk Vistain

0.1% WRMS (weighted RMS). You can still find this ar-rangement in low- and mid -fl machines.

True servo systemsDuring the late 1970s, growing user sophistication and

the inevitable specification wars forced manufacturers to-ward true servo systems. Increased availability of ICsmade fabrication more practical and less expensive.

Two types of servo emerged. At the lower end of themarket were FG (frequency generator) designs, and at thetop, crystal -controlled designs. Figure 2 shows a typicalFG phono servo that yields a typical flutter figure of0.045% WRMS, quite respectable for an analog system.

Mounted inside the motor is a Hall -effect sensor, whichvaries its output voltage depending on the strength of themagnetic flux field around it. Rotation of a magnet gangedto the motor shaft causes a varying voltage output fromthe Hall -effect device, the net result being a sine wave fre-quency that directly tracks motor speed. This is the feed-back component necessary in a servo.

Within IC101, the signal is amplified, level -shifted andsquared by the Schmitt trigger between pins 5 and 6. Thenit's compared to a sawtooth wave with characteristics setby the variable resistors VR101 or VR102, depending onthe position of the speed selector 5101. VR103 providesfine pitch control for either speed. Within IC101, the posi-tion of the squared FG signal samples the reference rampvoltage, the output becoming the servo correction voltage,which is amplified by Q101.

The normal operating point of the circuit is set so that,at the correct speed, the FG signal samples the ramproughly in its center. If the speed decreases, the FG fre-quency decreases and samples the ramp at a lower volt-age. The servo then applies a correction signal in an at-tempt to sample the ramp at the designed operating point.In other words, it speeds up the motor. The reverse occursif the motor runs too fast.

Stability of this circuit depends on the quality of the com-ponents forming the sawtooth generator's RC network.The built-in strobe used by the operator for speed adjust-ment is no more than a neon lamp across the mains, sospeed accuracy will depend on the line frequency unless itis set with a test record and frequency counter.

TroubleshootingLet's say our example phono exhibits severe speed irreg-

ularity. We make a mechanical check. The table rotatesfreely, the belt seems good, the motor shaft turns smooth-ly with no rough spots or odd noises. PS voltage is on themoney. Do we have a bad motor, servo IC, or what?

Looking at the FG signal is fruitless. It's there all right,and relatively clean, but the frequency varies erratically.The sawtooth at IC101, pin 9 is a perfect replica, of what'son the schematic. (Given the quality of service information,the skeptic might find that highly unusual.) Next, see if themotor will run smoothly when freed from the servo.

You'll notice that the waveform feeding the base of mo-tor drive Q101 is do with a small component of ac at thesawtooth frequency riding on top. All the same, a do volt-age of about 1.5V substituted at this point ought to makethe motor turn at roughly the correct speed. Aha! Theplatter rotates erratically, probably because of a bad com-mutator or brush inside the motor.

Theroad to successstarts with onestep ín the rightdirection.And that first step is an important one - finding onecompany with the parts, service and delivery youneed to run your business efficiently!

We know we have the answer... MCM Electronics.Our latest catalog contains the wide selection ofparts and equipment you're looking for - at verycompetitive prices.

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MCM ELECTRONICS858 E. CONGRESS PARK DR.CENTERVILLE. OH 45459

A PREMIER CompanyES -28



Readers' Exchange

Editor's note: Readers' Exchange items are published in the orderthey are received. We are happy to offer this service at no charge toyou, our readers, but ask that: Items are legibly written or typed. Your name and address are included on the same page as youritem (envelopes and contents often become separated). Phonenumbers also may be included. Using your peel -off label is a goodidea. You limit any item to no more than three units.

Please understand that ES&T is in production six weeks to twomonths ahead of publication date.

No ad requests will be accepted for Readers' Exchangewithout a full, verifiable name, address AND phonenumber. This information is necessary for ES&T files.Phone numbers will not be published, if so requested.

Wanted:

Sencore CG25 color -bar generator; variac; isolation transformer. GeorgeDemaris, 7387 Pershing Ave., Orlando, FL 32822-5743; 305-277-3746.

Plastic battery holder, new or used, for Panasonic AM/FM radio model728; dual VC & SW, new or used, for Panasonic AM/FM stereo model RE7671 (Sams 960), new part no. EVG765U40A53, old part no. EV-FK12L50A53. William J. Maida, 274 W. Sabal Palm Place, Longwood, FL32779; 305-869-6138.

Two MRF 455A transistors; five 7868 tubes; 10 #12, 6V lamps for BogenPA amps; one each bandswitch for Panasonic RF 2800 receiver #RSR 98W

NESDAComputer GroupCOMPUTER SALES AND SERVICE DEALERS

WORKING TOGETHER

I Y 1.01.'yAl

1YvY' ` k w,

JI!Iply w1ll,/Nrll:uil7:1'

.ili'rb'!. 14

E Service training.

Assistance inselecting in-houseequipment andsoftware.

Specialized soft-ware for service

management.

Factory contacts for service literature and parts.

L I involvement in a stable and productive nationaltrade association.

FOR MORE INFORMATION SEND BUSINESS CARD TO:NESDA COMPUTER GROUP, 2708 WEST BERRY STREETFORT WORTH, TEXAS 76109; PHONE (817) 921-9061

I

or equivalent; one printer and disk drive for the Tandy Color Computer IImodel 26-3127; and one each Z-80/CPM for the Apple IIe pro system. Stateprice and condition. Mike Adams, Haney Vo-Tech Center, 3016 Hwy. 77,Panama City, FL 32405; 904-769-2191.

Service literature and repair manual for Rutherford stereo, model 73,chassis no. X9120U. Will pay for copies. Mike Uhlich, 3329 Marsrow,Toledo, OH 43615; 419-841-8914.

Source of "Standard HV transistor 508" or ECG equivalent; source ofTA7147 video IC. James C. Langford, 2202 Frankfort, Richland, WA99352; 509-946-1455.

Service manuals and source of replacement parts for older tube -type homeand auto radios manufactured by Blaupunkt, Telefunken, Pye, Smith,Becker, Condor, etc. Wilford Wilkes, Box 103, Brisbin, PA 16620;814-378-8526.

New or used flyback transformer for a Quasar model series, using chassisseries AFTS-942 through YKTS-942; the transformer part no. is24D71542A15 (preferably) or 24D72686A03 (secondarily). Please quoteprice. N.B. Taylor, Box 392, Atascadero, CA 93423.

New or used take up and supply platter with spindles for Akai reel-to-reeltape player, model 280DSS. Bob Moole, Waiters Appliance Center, 528North Court, Carroll, IA 51401; 712-792-2525.

SAMS Photofacts nos. 1,500 to 2,000; schematic for Advent projectiontelevision, model VB-761, or source for service data. Wilfred Forgue, Wil-ly's Electronics, P.O. Box 56595, North Pole, AK 99705; 907-488-1307.

For Sale:

Sencore L/C 53 coil and cap. analyzer Z -meter, recently factory calibrated,good condition, new leads and cable, $600; Sencore SC60 widebander, goodcondition, all probes and leads, operator's manual, $950. Joseph W. MarshSr., 3118 E. 14th St., Port Arthur, TX 77640.

Moving?Take us with you.Just peel off the subscription mailing labeland attach it to the address change cardlocated at the front of this issue. Pleaseallow 6-8 weeks to process your addresschange.

IGOTROHIGServicing &Technology


More than 100 new and used television and stereo tubes, send s.a.s.e. forlist. Ed Burgad, 715 Interstate Ave. 21, Bismarck, ND 58501; 701-224-8210.

Many Zenith modules and yokes, from $5 to $12.50-send s.a.s.e. for list;800-304-S-55855 remote repair kit, $3.50. M.E. Andrews Jr., Box 91, Ex-eter, RI 02822.

Sencore VA62 with NT64 and VC63TP212 in original box with all manuals,$3,000; NAP1714550005 VCR tool kit, $500. Kenneth Morvant, 5415White's Ferry Road, #68, W. Monroe, LA 71291; 318-396-8346.

Sencore SC61 waveform analyzer, including direct probe DP226, $2,500;Sencore LC53 Z -meter, including SCR -224 SCR and triac test accessory,$550; all in excellent condition. Jens Clark, P.O. Box C, Charlottesville, VA22903-0517; 804-979-0187 evenings.

Diehl Engineering Mark V diagnostic computer, new, $445; Mark III, new,$195. Make offer. Duane Conger, 4321 Herrick Lane, Madison, WI 53711;608-238-4629.

Sencore VA48 video analyzer with manual and leads, excellent condition,$475. B&K digital IC color generator with manual and leads, excellent con-dition, $150. John A. Arrington, 2545 Andorra Drive, Hephzibah, GA30815; 404-798-7711.

Sencore LC53 Z -meter, $500; SCR 224, $20; SCR 250, $100; VA48analyst, $750; SC60 scope, $800; FC71 frequency meter, $500; CB49analyst, $650. Ronald MacKenzie, 41 Wheelwright Lane, Levittown, LongIsland, NY 11756; 516-579-8546.

Test jig with Telematic adapters: YA:12,14,15,21,49; CD:51,53,59,63,67;SYA:887-$35. SCR -221 electrified frequency meter, $45. All excellentcondition. QST: Aug., Sept., Nov., Dec. 1971; Jan. -Aug., Dec. 1972; Feb.,April, June, July 1973-make offer. William J. Maida, 274 W. Sabal PalmPlace, Longwood, FL 32779; 306-869-6138.

Resistors, capacitors, diodes, transistors, IC chips, thousands of repairparts; Sam's #1017-2231, from $1.50 each; factory service manuals, how-toelectronics books, courses. Send 22¢ stamp for description and price list.

Dean Ambrose, Midwest Electronics, 1203 Park Drive, Wilmington, IL60481; 815-476-7095.

Kikusui C0S5060 scope, 60MHz bandwidth, 3 vertical inputs, withoperating and service manual, $800. B&K 3020 sweep/function generator,$200. Both in excellent condition. John Vitale, Vitale's Electronics, R.D. 6,Box 303, Newton, NJ 07860; 201-383-5565.

Sencore SC61 waveform analyzer, one year old, used four times, $2,500.David; 904-755-4981.

Diehl Mark V, new, $375; Mark III, new, $200; both never used, in boxes,with manuals. McCormick TV, 824 Woodrow Lane, Denton, TX 76205;817-566-0774.

HP model 130C scope, 500kHz bandpass, dual amplifier inputs for X -Y,phase or any sweep measurements, $195; Dumont model 1062 scope,50MHz bandpass, dual amplifier inputs, main and delay sweeps, 100% solidstate, $400; Diehl model Mark III scanner, $250. Add $15 for insured ship-ping on any of these. Fred Jones, 407 Morningside Court, Niceville, FL32578.

B&K 820 capacitance tester, $85; B&K 667 tube tester, $35; B&K TR110Isotap transformer, $85; Diehl supertech Mark V scanner, $325; EICO 944flyback/yoke tester, $65; all in excellent condition. Will ship UPS COD.Amado Ramos, 428 Wolford Drive, Spring Valley, CA 92077; 619-267-7673.

Sound Technology FM alignment generator, model 1000A, very good con-dition, $900. Ken, Martha Lake Electronics, 16521 13th Ave. W., Lynn-wood, WA 98037; 206-743-4178,

HP H-P41CX hand-held computer, $100; B&K 466 CRT tester and re-juvenator, $60; RCA 10J106 color test jig with RCA and Zenith adaptersand manual, $100. Dennis Dillon, 1616 S. 94th St., West Allis, WI 53214;414-774-2255.

Philco Junior scope, model 7019, $25; RCH Junior voltohmyst, $25;capohmist, $25. Alexander Crispo, 3225 Chipmunk Drive, New Pt. Richey,FL 34653. EISVU

Advertising rates in the Classified Section are 85cents per word, each insertion, and must be accom-panied by payment to Insure publications.

Each Initial or abbreviation counts a full word.Minimum classified charge is $20.00.For ads on which replies are sent to us for forwarding(blind ads), there is an additional charge of $30.00 perInsertion to cover department number, processing ofreplies, and mailing costs.Classified columns are not open to advertising of anyproducts regularly produced by manufacturers unlessused and no longer owned by the manufacturer ordistributor.

FOR SALE

AUTOMOBILE RADIO and tape replacement parts.Delco, Chrysler, Philco-Ford, Motorola, Panasonic al idmany others. Large inventory. Laran Electronics, Inc.,3768 Boston Road, Bronx, NY 10469. (212) 881-9600.National (800) 223-8314, NY State (800) 446-4430.

1 -85 -tin

VCR REPAIR SOLUTIONS FOR VHS MODELS. Volume1.150 Symptoms and cures -$11.95. Volume 2-$11.95.All 300, $19.95. Eagle Electronics, 52053 Locks Lane,Granger, IN 46530. 12-87-61

SERVICE MANUALS. Large Shop has 18 yr. collectionof duplicates. All original manufacturer. All new.Audio $1.00, video $5.00. Send SASE for list. TapeRecorder Clinic, 4850 E. Speedway, Tucson, Arizona85712. 11.86 -tin

TVNCR "Tuff Tips" listed by mfg. and model. 1st edi-tion -200 TV/VCR tips $10.95. 2nd edition -200TV/VCR tips $10.95. both editions $19.95. For TV tipsonly -1st or 2nd edition $5.95. both editions $10.95.For VCR tips only -1st or 2nd edition $6.95. both edi-tions $12.95. TECH CURES, 4825 FredericksburgRoad, San Antonio. Texas 78229. 11.87.2t

TVNCR FAILURE HISTORIES-Multiple cures formost problem areas. Send $6.95 with mfg. and modelnumber to TECH CURES. 4825 Fredericksburg Road.San Antonio. Texas 78229. Money will be refundedwith free sample. If model is not on database. 11-87-2t

TV TROUBLESHOOTING: 130 Problems -Solutionsplus 12 steps to easier repairs. $12.00. RemarkableDiagnostic tool. measure high voltage performance.no mistakes. $5.00. Jones. Box 702. Niceville. FL32578. 11-87.3t

"THE WORKBENCH COMPANION"-Over 200 pagesof Tough Dogs and troubleshooting notes from 20years in the business. Partial contents: Symcure Index1970-1987, Radio Elec. Clinic 1969-1987, ETD IndexColorFax 1969-1982, Testing HV Diodes, Int. Flybacks,Zenors, etc. Important note on capacitors and muchmore. Price: $29.95 + $2.50 shipping and handling.FARRELL ELECTRONICS, HI-Teck, Larry Gribbin,Chief Engineer, 127 Providence Avenue, SOUTHPORTLAND, MAINE 04106. 10-87-31

TV TOUGH DOGS: 300 symptoms and cures. Send$7.95 to DAVIS TV, 11772 Old Fashion Way, GardenGrove, CA 92640. 10-87-tfn

SONYTRINITRON Rebuilt Picture Tubes are nowavailable. All tubes shipped U.P.S. No Charge. We buyall Sony duds. Rochester Kinescope. 716-235-0750.

11-87-t f n

PHOTOFACTS: Individual folders #1 to #1400 $3.00.Above #1400 $5.00. Sent same day first-classpostpaid. Loeb, 414 Chestnut Lane, East Meadow, NY11554. 12-87-6t

FOR SALE: Sencore LC 53 Z meter $500.00; SCR 224,$20.00; SCR 250, $100.00; VA 48 analyst, $750.00; SC60 scope, $800.00; FC 71 Freq. meters, $500.00; CB 49analyst, $650.00. Ronald MacKenzie, 41 WheelwrightLn., Levittown, LI NY, (516)579-8546. 12-87-1t

VA48 SENCORE ANALYZER, 21/2 years old. COM-PLETE WITH ADAPTERS & OWNERS MANUAL.$600.00. PH. 1-702-363-6746. 12-87-1t

VCR REPAIR SOLUTIONS FOR VHS MODELS. VolumeI-150 Symptoms and cures-$11.95. Volume II-$11.95. All 300, $19.95. Eagle Electronics, 52053 LocksLane, Granger, IN 46530. 7-87-6t

LASERS: 5mw helium -neon. Good for visual effectsuse, leveling, holagraphy. $175. Call 714-956-8497 orwrite MWK Industries, 1724 W. Ball #6, Anaheim, CA92804. 12-87-1t

LIKE NEW: Sencore-SC61, TF46, PR57, VA48, BE156,TC 162, CR 168, Handy 75. B&K-1450B oscilloscope,1602 H.V. power supply. All leads, accessories &manuals included. Best offer. 618-272-5171. 12-87-1t

TV LINE SELECTOR. Composite video in. Outputs in-clude pulse on selected line and all possible syncs.Differentiates between odd and even fields. UniqueElectronics, 16 Morningside Drive, Yardley, Pa. 19067.

12-87-11

VCR CROSS-REFERENCE LISTINGS for the followingelectronically similar manufacturers: RCA, GE,Sylvania, Panasonic, Quasar, Magnavox, Philco andJ.C. Penney. Send $13.95 to TECH CURES, 4825Fredericksburg Road, San Antonio, Texas 78229.

12-87-1t

SERVICES

Credit Repair, Business and Commercial LoansBrokered, Small Business Consultant. Free details.Commercial Financial Group, P.O. Box 920957, Dept.241, Houston, Texas 77292-0957. 12-87-1t


BUSINESS OPPORTUNITIESTVNCR SALES & SERVICE; well established, fullyequipped. Located in northern Virginia, highestgrowth area in U.S. Retiring because of healthreasons. Call 703.972-7027 after 7:00 PM EST. 12-87-tfn

FLORIDA SUNCOAST-T.V. Sales & Service. 26 yearssame location. Owner wants to retire-will trail &finance good technician. 813-746-2404. 12-87-1t

TVNCR REPAIR SHOP, For Sale. Parts, Equipment.Established, good lease & location. Nice shop,$25,000.00. 713-541-0260. Houston, Texas. 11-87-21

Training InstructorVideo Recorders

Matsushita Services Company, a divi-sion of Matsushita Electric Corpora-tion of America, is a dynamic serviceorganization with a nationwide net-work of dealers servicing consumerelectronic products.National Headquarters is seeking avideo technical training instructor toprepare and present technical train-ing seminars to service technicianson product troubleshooting andrepairs.A professional knowledge of theories.principles and techniques of elec-tronic engineering, education, skillstraining and troubleshooting pro-cedures required. Excellent verbaland written communication skills areexpected. Prior teaching experienceand computer skills are desirable.An Associates or Bachelors degree orequivalent experience in the con-sumer electronics field is required.VCR experience a must. Some travelwill be required.We offer an attractive salary, liberalbenefits as well as a rewarding andchallenging environment. Pleasesend resume with salary history to:Joan Soga, Dept. M1288, PASC MAT-SUSHITA ELECTRIC CORPORATIONOF AMERICA, 1 Panasonic Way.PANAZIP 4A-7, Secaucus, NJ 07094An Equal Opportunity Employer M/F.

MatsushitaService Company

TV "TECH'S" DREAM

TEST & RESTORE EVERY CRT on the marketwithout every buying another adaptor socket foryour CRT tester. Fits ALL makes & models.MONEY BACK GUARANTEE. Over 12,000 sold.Complete Patented Kit, with Sockets & SetupBook Only $63.95 ppd. A one-time investmentfor life!! Visa/MC/COD's/Checks.

FREE CALL 1-800-331-9658DANDY MFG. CO.

2323 Gibson Street Muskogee, OK 74403


Day

HAND REMOTE REPAIRLA GUARDIA ENT.

5882 Rich Hill WayYorba Linda, CA 92686

(714) 579-1276 Call for pricing 24 hr turnaround time Return freight pre -paid


Ad Index/HotlineReader

Page Service AdvertiserCompany Number Number Hotline

All Electronics Corp. 26 21 800/826-5432A.W. Sperry 5 10 800/645-5398Atrix, Inc 29 25 800/222-6154B&K Precision Dynascan Corp. IBC 2-7 312/889-9087Beckman Industrial Corp. IFC 1 619/495-3200C + S Sales 41 28 800/292-7711Chemtronics, Inc 43 31 800/645-5244Cooks Inst. Elec. Engrg. 42 30 601/371-1351Dandy Mfg. Co 68 42 800/331-9658Digitron Electronic 28 24 800/526-4928E -Z -Hook 49 35 818/446-6175Electronic Parts Supply 14 14 800/227-0104ETA 50Fluke, John Mfg. Co., Inc. 3 9 800/227-3800Fordham Radio Supply Co 11 12 800/645-9518Iscet 50J.C. Penney Co. 47 33 404/961-8400Jensen Tools Inc 50 45 602/968-6231Joseph Electronics 16,24 16,19 800/323-5925Laguardia Enterprises 68 43 714/579-1276M.A.T. Electronics 63 46 800/628-1118MCM Electronics 65 41 800/543-4330NAP Conusmer Electronics 27 23 615/475-0044N ES DA 53,66NTE Electronics, Inc. 1 8 800/631-1250OK Industries, Inc. 23 18 800/523-0667Panavise Products Inc. 39 27 213/595-7621Parts Express Intl Inc 45 32 513/222-0173Projector Recorder Belt Corp 30 26 800/558-9572PTS Corp. 25 20 812/824-9331Sencore, Inc. 55,57,59,61 36,37,38,39 .800/843-3338Sony Service Company 7Sperry Tech, Inc 68 44 800/228-4338Techni-Tool 26 22 215/825-4990Tektronix, Inc 9,15,19 11,15,17 ... 800/433-2323Tektronix, Inc 8A -8B 800/433-2323Tentel 14 13 800/538-6894Tronix, Inc. 48 34 313/939-4710U -Can -Do VCR Educational Products Co. .42 29 513/548-6113Zenith BC

Tech'sGuide

ToPricing ; V

"Tech's Guide ToPricing"updated new 5th edition aframework for setting ratesthat apply to Hi -Tech pro-ducts ...a formula thatguarantees SUCCESS!Call Toll Free for details 8/51-800-228-4338 CST


ELECTRONIC SERVICING & TECHNOLOGY Volume 7, No. 12(LISPS 462-050) is published monthly by Intertec PublishingCorp.. 9221 Ouivira Road, P.O. Box 12901, Overland Park.KS 66212. Second Class Postage paid at Shawnee Mission,KS. and additional mailing offices. POSTMASTER: Send ad-dress changes to ELECTRONIC SERVICING & TECHNOLOGY.P.0 Box 12952, Overland Park, KS 66212-9981.

ADVERTISING SALES OFFICES

ELECTRONICServicág&Tec nology

ALL U.S. TERRITORIESGreg Garrison, Sales ManagerP.O. Box 12901Overland Park, KS 66212Phone: (913) 888-4664Fax: (913) 888-7243Telex: 42-4156 INTERTEC OLPK

NORWOOD, AUSTRALIAHastwell, Williamson, Rouse PTY. LTD.P.O. Box 419Norwood, S.A. 5067Phone: 332-3322Telex AA 87113

LONDON, ENGLANDNicholas McGeachinRoseleigh House, New StreetDeddington, Oxford OX5 4SPPhone: (0869) 38794Telefax: (0869) 38040Telex: 837469 BES G

TOKYO, JAPANHaruki Hirayama,EMS, Inc.Sagami Bldg., 4-2-21, Shinjuku,Shinjuku-ku, Tokyo 160, Japan(03) 350-5666Telex: 2322520 EMSINCJCable: EMSINCPERIOD


HANDHELD DIGITAL IC COMPARATORTESTERS FEATURE 20 CHANNELLOGIC MONITORB&K-PRECISION's Model 550 and 552 ICComparator Tester/Logic Monitors test IC'sby comparison to a known good reference inone simple operation. As logic monitors, theysimultaneously indicate the logic states of up to20 IC pins. They test most 14 to 20 pin, 54 and74 Series TTL (Model 550) or 4000 and 74CSeries CMOS (Model 552) devices. Bothmodels are available from distributors at$395. Contact your local distributor or:B&K-PRECISION, Dynascan Corp., 6460W. Cortland St., Chicago, IL 60635. (312)889.9087. Circle (2) on Reply Card

NEW COMPARATORADDS IC/COMPONENT TESTING TO SCOPE

Test virtually any type of passive or active componentor module with B&K-PRECISION's new 541 Com-ponent Comparator. The 541 is designed for use withthe 540 component tester or virtually any x -yoscilloscope. It is well suited for both in -circuit andout -of -circuit tests. It's fast and easy to use. Unlikesingle function testing, the 541 can be used on series,parallel or series/parallel circuits. $395. Contact yourlocal distributor or: B&K-PRECISION, DynascanCorp., 6460 W. Cortland St., Chicago, IL 60635.(312) 889-9087. Circle (4) on Reply Card

NEW COMPONENT TESTER LOCATES FAULTSON UNPOWERED BOARDS IN FIELD OR PLANTThe new Model 540 component tester is an extremelycost effective, highly flexible trouble -shooting aid thatcan assist in rapidly locating faults on unpoweredboards. Faults can be traced to the component levelwithout specific circuit knowledge. Individual com-ponents can also be tested. Test results are displayedas a curve on a built-in CRT display. Curve tracingallows matching of components. Two channels allowproduction testing against known good boards. Idealfor field service or production testing. $995. Con-tact your local distributor or: B&K-PRECISION,Dynascan Corp., 6460 W. Cortland St., Chicago,IL 60635. (312) 889-9087.

Circle (5) on - eply Card

PROGRAMMABLE IC TESTER TESTS TTL,CMOS, RAM AND ROM IC'S, IN OR OUT -OF -CIRCUITCalled the "first cost-effective way to test IC's both inand out -of -circuit," the new B&K-PRECISIONModel 560 fills the void between basic componenttesters and costly ATE systems. Over 1500 different14 to 24 pin devices can be tested, including TTL andCMOS digital IC's, RAMs and ROMs. The 560speeds testing, simplifies diagnostics and doesn't re-quire prior test skills. Plain -English user promptsguide every step of operation. Test results are dis-played as positive "pass" or "fail." Test results can befed to a printer. Applications include incominginspection, QC, production line testing andtroubleshooting faulty products. $3,500. Contactyour local distributor or: B&K-PRECISION, Dynas-can Corp., 6460 W. Cortland St., Chicago, IL 60635.(312) 889-9087. Circle (7) on Reply Card

LOGIC/PULSER PROBES HELP LOCATE DIGITALFAULTS IN LAB OR IN FIELD SERVICEB&K-PRECISION now offers logic and pulser probesto fill the needs of engineers and technicians. The DP -21is a 20 MHz probe that also displays pulse presenceand logic status. Both LED and audible logic stateindicators are featured. The DP -31 pulser probecan be used alone or with a logic probe or scope. Itproduces a 10µS pulse at 0.5 or 400 PPS ratesand features an external square wave andsynchronizing terminal. Both probes aremulti -family compatible. The DP -21 is$32. The DP -31 is $33. Contact yourlocal distributor or: B&K PRECISION,Dynascan Corp., 6460 W. Cortland St.,Chicago, IL 60635. (312) 889-9087. Circle (3i on Reply Card

F11:17:11Will

rogrammabl ircuit IC tester

crtable curve -tracing component testercrtable IC comparator testerriogic monitors

enchtop IC component comparator testerulti-family compact pulser probes

emory-mode multi -family logic probes

Whether your needs are for production board testing, incoming inspectionor field service. B&K DRECiSION has you covered with time saving, accuratedigital test products.

The Model 560 Programmable In/Out-of-circuit IC Tester is the firstcost-effective way to rapidly test IC's both in and out -of -circuit. Punch upthe number you need from a resident memory of over 1500 TTL, CMOS IRAMs and ROM'S.

The Model 540 Component Tester locates faults on unpowered boards,down to the component'evel. Curve -tracing method also allows fast con-parison of components or boards.

The Model 541 Component Comparaor is a companion instrumentfor use with your scope or the 540. It tests C's, semiconductors, capacitors.inductors. transformers and more.

The Models 550 and 552 IC Comparator Tester/Logic Monitors arehand-held portables for TTL and CMOS applications. In -circuit dynamictests compare a known -good IC to an on-bocrd IC. A 20 -charnel logicmonitor is built-in.

The B&K-PRECISION digital test line-up is rourded out by convenient andeconomical p Jlser and logic probes.

For immediate delivery or complete specifications and applicationsinformation, call your local distributor or B&K-PRECISION.

DYNASICAN CORPORATIDN6460 West Cortland St. Chicago, IL 60635 312-889-9087

lntemationalSales, 6460 W. Cortland St., Chicago, IL 60E35

Canadian Sales, Atlas Electronics, OntarioSouth and Central American Saes, Empire Exporters, Plainview, NY 1'803


Zenith remanufactured and reconditionedreplacement modules and sub -assemblies

factory -freshfrom Exchange Counters

throughout the U.S.There's no sense risking.

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One of the easiest, fastest,and surest ways for you to pre-serve the pedigree of the Zenithproducts you service and maintain iswith genuine Zenith replacementparts.

And at no time is this more criticalthan when you replace the more so-phisticated components like modules,tuners, channel selectors and sub-assemblies.

Your participating Zenith partsdistributor will supply you with areplacement remanufactured, recon-ditioned and serviced for reliability byZenith people as dedicated andknowledgeable as those who madethe original.

Ecually important, the replace-ment module or sub -assembly youreceive in exchange from your Zenithparts distributor will most likelyincorporate Zenith factory modifica-tions, if any, in effect at the time ofremanufacture.

And nowhere else but in a par-ticipating Zenith parts distributor'sExchange Program can you getassurance that a replacement incor-pora -es a Zenith factory up -date ifone exists!

FM/TN

That's why youshould start taking

advantage of yourZenith parts distributor's

R&R Exchange Program now.We'll help you locate the Zenith

R&R Exchange Counters in yourarea if you'll write on your companyletterhead with your complete addresselement and Zip Code.

Chances are there's an ExchangeCounter for Zenith factory -freshreplacement modules and sub-assemblies closer than you realize.

Write, if you don't know, and we'llcell you where it is! There's no senserisking an exchange for a Zenithreplacement anywhere else!

t

The quality goes in before the name goes on.®

Zenith Service, Parts & Accessories/11000 Seymour Avenue, Franklin Park, IL 60131/A Division of Zenith Electronics Corporation

Documents

The how-to magazine of electronics AN INTERTEC PUBLICATION ...americanradiohistory.com/Archive-PF-Reporter/80s/EST-1987-12.pdf · The how-to magazine of electronics... AN INTERTEC