servicing &technology - american radio history:...

The how-to magazine of electronics...

Servicing &Technology

1

February 19861$2.25

Splish, splash...flood-damaged electronic equipment

"I'll tellyou what it takesto succeed inVTR repair service:'

"It takes know-how, and theright equipment to do the job.You obviously have the know-how, or you wouldn't be readingthis nagazine. The equipment?The same brand that factoriesuse to build and test sets onproduction lines... LEADER!"

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To see what you're getting,Leadar's LBO -525L 50 MHzdual --race oscilloscope is a natural.Put tf-e input to a circuit on onetrace. the output on the other, andactually see where distortion

Photograph. oftest bench takenat Oren -Tech, Inc.a factory authorizedservice censer.

occurs, how much, and when it'scorrected! you'll find more fea-ureson this oscilloscope than on manyothers regardless of price ormanufacturer's claims. Or choosefrom a cozen other models.

The Leader frequency counter -in a rugged metal housing -can beused to adjust chroma frequencyand vertical or horizontal synchcircuits. Leader's large, brightfluorescent displays are easy toread. Tc round out your test beach,you'll need a wow and fluttermeter, mirror -backed scale acvoltmeter, and a good quality fieldstrength meter... all from Lead ar.

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Introducing the AWS DML-4020,2 -Channel Data Logging Digital Multimeter

We all know how versatile one 31/2 digit autorangingdigital multimeter can be. Picture not just one but two suchpieces of microprocessor controlled test equipment in onepackage. Add to that the ability to use both DMM's indi-vidually or simultaneously to read and display similar ordisimilar functions.

And that's not all. Imagine how useful it would be tohave a numerical or graph printout of the values you'remeasuring.

Want more? How about being able to program a built-in comparitor with "high" and "low" limits on whateverfunction you're measuring, than have an array of five LED'sindicate where your actual readings are in relation to the"limits" you have set.

There's still more. Automatically sample a desiredfunction on any one of 12 different time intervals from every5 seconds to once per hour. Then simply push a button andget a printout showing the highest and lowest values, thenumber of times samples were taken, and the average valueof the function you've been measuring over an extendedperiod of time (up to 30 days).

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For more information write or call your distributor orcontact A. W. Sperry Instruments Inc. 245 Marcus Blvd.,Happauge, N.Y. 11788 (800) 645-5398 Toll Free. (N.Y.and Alaska call collect (516) 231-7050).

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The how-to magazine of electronics...

GIGOTROAIOs Volume 6, No. 2 February 1986

11111111~111'

10Servicing WardsHV and LV circuitsBy Homer L. DavidsonRead where to directsuspicion when modelGGY16229A color receivergoes completely dead: Mostrepairs will be required inthe voltage -supply circuits.

22Solder: the tin tiethat bindsBy Conrad PerssonSolder hasn't changed, butthe size of components andwiring and the rules fcrsoldering them to theircrowded boards havechanged dramatically.

37More on thetelephone testerKey information previouslyomitted by the author,together with detaileddrawings, are presented forclarification of an ES&TNovember 1985 articledescribing telephone -testerconstruction.

page 22

Soldering/desoldering techniques havechanged because of the susceptibility todamage of today's delicate com-ponents. (Photo courtesy of Pace Inc.)

page 6

Recently developed software may leadto a technician -assist computer systemfor diagnosing ailing circuitry. (Photocourtesy General Electric.)

Departments:4 Editorial5 News6 Technology

29 Profax55 Literature56 Books57 Products62 Reader's Exchange63 Photofact

49Splish, splash: repairingflood damaged electronicequipmentBy Joseph J. Carr, CETIs there life after waterdamage? Whether fromflood or faucet, suchdamage can be reversed ifelectronic equipment ishandled according toprocedures describedby the author.

52What do you know aboutelectronics? The padder-againBy Sam WilsonPursuing controversyengendered by a previousarticle, more about padderadjustment: on the high orlow end of the band, andwhat is the determinant?

60Test your electronicknowledgeBy Sam WilsonThis month's quiz is sounddirected-think audio!

2 Electronic Servicing & Technology February 1986

The technology isadvanced. The

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ensures that no high voltage spikes or magnetic fields will be present on the soldering tip.These technologically advanced stations are capable of handling all the delicate

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Editorial

Themore

thingschange

gas

The old French saying goes, "Themore things change, the more theystay the same." Nowhere is changemore evident than in the electronicsindustry. Yet if you look beyond thesurface, it's also evident that in spiteof massive and continuous change,many things are the same today asthey were when electronics was in itsinfancy.

For example, as we point out inthis issue in the article on soldering,today's tiny components andintegrated circuits are soldered to theprinted circuit board, just as thetubes and other components ofyesterday's electronics products weresoldered into their circuits. Today'scolor TV signal is still based on theNTSC standard that was establishedback in the days of black and white.Today's color television still deliversits picture via a CRT, just as the firstcommercial TV sets did many yearsago. (As pointed out in an article onLCD -TV displays in January's ES&T,though, this may change.)

If you could sum it up, it wouldprobably be that although theexternals, the technology, the detailshave changed, to a degree that itmakes the newer products and theirfunctions almost unrecognizablecompared to the old, the principles onwhich the products function have notchanged.

Take video recording, for example.Today's home video recorders giveusers a movie theater in their ownhome. They provide a beautiful TVpicture and stereo high fidelity sound.And all you have to do is buy or renta cassette and pop it into your VCRto transport yourself visually andaurally into a different world. It's afar cry from the early days of wireand tape recording when you couldbarely get a low fidelity tape to giveyou recognizable words. But theprinciple is exactly the same: Theinformation played back from the

tape in both cases was encoded onthe tape as magnetic impulses. Thedifference is that the circuitry forrecording and playing back the tapehas been improved. Even though thetape itself is an impressiveimprovement over earlier tapeformulations, the principle is still thesame.

This also is true with audio.Vacuum tubes have been replacedwith transistors and ICs, metalchassis have been replaced withprinted wiring and the fidelity of thesystem has been consistentlyimproved. Recordings have beendigitized. Admittedly, that opens upan exciting new dimension. But lookat what has remained unchanged.Start with the speakers: They remainbased on the old principles ofelectromagnetism or electrostatics,just as the earliest speakers were.Today's turntables, tonearms andcartridges, although far advancedbeyond the capabilities of early units,still use the same principles togenerate the sound signal. And eventhough digital audio is based on somenew developments, the disc, smalland shiny though it may be, still goes"'round and 'round" and must be readby some kind of stylus.

Look at any electronic device,consumer electronics or sophisticatedtest gear. A great deal has changed.In various portions of the equipment,digital has replaced analog,semiconductor has replaced vacuumtube, liquid crystal display hasreplaced meter movement. But a lookbeyond those surface changes revealsa product that's based on the sameprinciples as were based the earliestdevices. When you look at it this wayto reaffirm the timeless, underlyingprinciples of electronics instead ofbeing dazzled by all the innovations,you will maintain the perspective thatmakes servicing the new productsmuch easier.

clASLt


Enhanced -LCD products$3.7 billion market by 1992

A new report from StanfordResources, "Flat Panel Displays:The Impact of Enhanced-LCDsOn The Market For High Informa-tion Content Displays," forecaststhat the worldwide market formodules including these displaydevices will grow from $126million in 1986 to $3.7 billion in1992. This sales growth will bedriven by the use of enhanced-LCDs in new products and applica-tion; not by the replacement ofCRT displays in today's products.

Enhanced LCDs use a thin filmsemiconductor device at each ele-ment (pixel) in the display to over-come a number of current short-comings with multiplexed LCDs.(See January 1986, ES&T.)

The active matrix concepts weredeveloped more than 15 years agothat are being implemented todayin small pocket -sized liquid crystalcolor televisions. However thedisplays were not manufacturableat that time because of the infancyof the high resolution fabricationtechniques required. The display

industry, using techniques devel-oped by the semiconductor in-dustry, has advanced to the pointwhere commercial products arenow available.

There are about 30 firms active-ly investigating flat panel displaysbased on thin-film devices. Thisnumber does not include theuniversities nor the dozens offirms conducting preliminaryresearch in the field.

As in many technology areas,the results obtained are propor-tional to the total amount ofresearch money spent. The com-bined annual worldwide researchand development expenditures forwork on thin-film based displays ismore than $100 million. Very fewtechnologies have been able toresist yielding products under suchintense cultivation.

Car of the future will arrivetalking and computerized

Television dramas of cars con-versing with their drivers, track-ing their location via computers,and so on, may seem farfetched,but those capabilities will move outof science fiction and into thedashboard by 1990, says a newstudy of the $4.5 billion escalatingU.S. market for non -entertain-ment automotive electronics.

"Electronics will soon become asignificant factor in the cost of theautomobile," predicts "Non -Enter-

tainment Automotive ElectronicsMarket" (#1542), a new report byFrost & Sullivan. The study pro-jects that devices ranging fromfuel -mixture sensors and multipur-pose CRT displays to keyless entrysystems and navigational elec-tronic compasses will contribute toa tripling of the market between1984 and 1990.

EIA study probes attitudesof audio consumers

A detailed attitudinal survey ofaudio consumers was released to-day by the Electronic IndustriesAssociation's Consumer Elec-tronics Group.

The 254 -page study, preparedunder the direction of CEG'sMarketing Services Audio Com-mittee, was distributed last monthto member companies and is nowavailable to non-members at a costof $750. Inquiries should bedirected to EIA/Consumer Elec-tronics Group, 2001 Eye Street,N.W., Washington, D.C. 20006202-457-4919.

Based on the results of morethan 1,600 interviews, the surveyprovides in-depth analysis of thepurchase behavior, attitudes,listening habits and audio equip-ment ownership of various con-sumer segments. Respondents hadpreviously been identified as re-cent purchasers of home, car orportable audio products. estirw

ELEOTROINC

Editorial, 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.

EDITORIALNils Conrad Persson, EditorCarl Babcoke, Consumer Servicing ConsultantDan Torchia, Group Managing EditorMarjorie Riggin, Associate EditorJoy Culver, Editorial AssistantDarrylI Fortune. Editorial Assistant

BUSINESSCameron Bishop, Group Vice PresidentEric Jacobson, PublisherGreg Garrison, Sales ManagerStephanie Fagan, Promotions ManagerKelly Hawthorne, Marketing AssistantDee Unger, Advertising SupervisorKaren Royal), Advertising Coordinator

ARTKevin Callahan, Art DirectorJoni Harding, Graphic Designer

ADMINISTRATIONR. J. Hancock, PresidentJohn C. Arnst, Circulation DirectorJo Ann DeSmet, Circulation ManagerDee Manies, Reader Correspondent

MP

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ELECTRONIC SERVICING & TECHNOLOGY (USPS 462-050)

(with which is combined Electronic Technician/Dealer) ispublished monthly by Intertec Publishing Corp., 9221Ouivira Road, P.O. Box 12901, Overland Park, KS

66212-9981. Second Class Postage paid at Shawnee Mis-sion, KS 66201. Send Form 3579 to P.O. Box 12952,Overland Park, KS 66212-9981.

ELECTRONIC SERVICING & TECHNOLOGY is the "how-to"

magazine of electronics. It is edited for electronic profes-sionals and enthusiasts who are interested in buying,

building, installing and repairing consumer electronicequipment. This includes audio and video equipment.microcomputers and electronic games.

SUBSCRIPTION PRICES: one year $18, two years $30.three years $38 in the USA and its possessions. Foreigncountries: one year $22, two years $34, three years $44.Single copy price $2 25; back copies $3.00. Adjustmentnecessitated by subscription termination to single copyrate. Allow 6 to 8 weeks delivery for change of address.Allow 6 to 8 weeks for new subscriptions.

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01986 All rights reserved.

February 1986 Electronic Servicing & Technology 5

GEN -Xsoftware

developedto assist

withservicing

Servicing home electronics prod-ucts keeps getting harder. Theproducts themselves have becomeincreasingly complex, with the ad-dition of ICs, start-up and shut-down circuits, electronic tuning,remote control, stereo -audio andmore. Not only that, but in addi-tion to TV and audio equipment,many of today's homes boast aVCR, a video camera, a microwaveoven, a cordless telephone.

The repair of all of these prod-ucts, with all of their sophisticatedelectronic circuitry, has becomethe responsibility of the technicianwho formerly repaired only televi-sions. The result is an almost im-possible learning task.

Wouldn't it be nice if there werea computer system that couldassist a technician in a step-by-steplogical diagnostic process, tailoredfor the specific product type.

Such a system does not exist-unfortunately. But softwarerecently developed ultimatelycould lead to a computer systemthat would be a valuable aid indiagnosing problems in consumerelectronic products.

Recently, General Electric Com-pany scientists unveiled softwarethat dramatically reduces the timeit takes to build expertsystems-the special programsthat enable computers to mimicthe reasoning process of humanauthorities on a given subject.Known as GEN -X, the new soft-ware will enable experts indiagnostics, maintenance andother fields to readily input theiraccumulated knowledge and ex-perience into a computer.

Developed at GE's Research andDevelopment Center in Schenec-tady, NY, the software was in-troduced at the Ninth Interna-tional Joint Conference on Ar-tificial Intelligence at the Universi-ty of California at Los Angeles.

According to Dr. Peter W. Dietz,manager of the GE R&D Center'sEngineering Information SystemsBranch, the new software hasseveral unique features, includingspecialized graphics such as easy -to -follow decision trees and rule

At GE R&D, Dr. Bruce Pomery, left, amember of the GEN -X developmentteam, diagnoses turbine faults for ArneLoft, consulting engineer with GE's Tur-bine Group, as he applies an expertsystem based on GEN -X software.

spreadsheets. "These graphics pro-vide people interested in develop-ing expert systems with a highly`user-friendly' framework in whichto organize their expert know-ledge," he said. GEN -X also has aunique modular design thatfacilitates testing, debugging, andadding rules, and is designed torun on conventional microcom-puters, Dr. Dietz added.

Development of existing first -generation expert systems has re-quired the services of highlyspecialized artificial intelligenceresearchers known as knowledgeengineers. These specialists havehad to conduct exhaustively de-tailed interviews with experts in agiven field in order to extract andinput their knowledge and reason-ing strategies. Some of today's ex -


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pert systems literally have takenyears to complete.

With the new software, by con-trast, the process can be reducedto a matter of months, and theassistance of knowledge engineerswill no longer be required formany applications. Scientists andengineers and others possessing abasic familiarity with computerswill be able to input their own ex -

Coming:the super -

smartcredit card

Did you ever think you'd be car-rying a microcomputer in yourwallet? Sounds far-fetched, but if ajoint development effort byToshiba Corporation and Visa In-ternational bears fruit, futurecredit cards, super smart cards,will be based on an intergrated cir-cuit containing a microcomputer.

This next -generation card' willhave a calculator -like keyboardand a display on the back, and abuilt-in battery (not seen in con-ventional IC cards) while retainingthe same size and thickness of thepresent credit card: 54mm long,86mm wide and 0.76mm thick.

Cardholders will choose whichaccount they want to use; check-ing, savings, credit or other ac-count, by pressing a key on theback of the card. They will entertheir personal identificationnumbers on the keyboard and theamount of the transaction. Thecard then will verify user identity,check the balance in the ap-propriate account, deduct theamount of the transactions andrecord it in the contained memorydevice. All these functions will beperformed without the need forany computer support. When in

pertise simply by following in-structions in a fill -in -the -blanksformat provided by the software.

The heart of any expert systemis its knowledge base or body ofknowledge, which includes a varie-ty of facts (pieces of evidence thatdescribe the problem) and rules(conditional statements that helpto define the solution to the prob-lem). Like repair personnel, an ex -

another country, the card willdisplay the amount of money con-verted to the country's currency.

In addition, the card will showthe time of the day and function asan electronic notepad for the card-holder's convenience.

These functions will make possi-ble a reduction in the burden andcost of communications with thecredit card company by banks andmerchants to check the identifica-tion and credit worthiness of theuser. Meanwhile, the card will givecardholders immediate controlover their financial assets.Simultaneously, the credit cardcompany will be better able to pre-vent counterfeit cards and the im-proper use of credit cards.

The new card also will be con-nected to Visa computers andbanks by using on-line cardreader/writer terminals at thestores so that the amount ofmoney will be deducted im-mediately from the user's bank ac-count. Furthermore, although itwill bear no magnetic stripe, thenew card can be used in conven-tional magnetic -stripe -reading ter-minals, the dominant terminals in

pert system relies on flexible,humanlike thought processes ("Ifthis and this are true, then dothis...") to diagnose problems,rather than on rigid procedures.

Expert systems contain hun-dreds of such rules generated fromthe real -life expert. It is this keyinformation that GEN -X is able toextract and encapsulate quicklyand accurately.

/71 ppR 1'D-46459/

Microcomputer -based "smart" creditcard will keep track of financial transac-tions as they occur. In addition, the cardwill show time of day and function as anelectronic notepad.

today's market, because the card isequipped to simulate a magneticstripe.

Visa International now issues130 million credit cards; it plans toreplace these gradually with thenew super -smart cards after com-pletion of various tests. Toshibaplans to discuss further details ofthe new card with Visa, and com-plete development by the summerof 1987, then start sampleshipments to Visa for field-testingat particular areas.

An IC card resembles a conven-tional magnetic credit card, butcontains a microprocessor and amemory device that allow it tostore 100 times as much data asmagnetic cards. Growing world-wide attention has been focused onthe IC card, because it can be safe-ly used in a variety of ways that in-clude identification and accesspasses, electronic banking, and forstoring personal records. sew


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Systems for Development. Productionand Repair of Electronic Assemblies

/

t.. r

ServicingWards NV and LV circuits

By Homer L. Davidson

Most repairs will be required in the various voltage -supply circuits. These include theline -rectified supply, the SCR regulator, the horizontal -sweep system, the start-up

circuit and the shutdown system. They are given the most coverage.

A large percentage of electronicfailures in the Wards modelGGY16229A color receiver(Photofact 2170-2 and photograph,see below) originate in the hori-zontal -sweep system and the low -voltage power supplies thatoperate with power from theflyback. These two general areasplus the input ac power, along withits rectification and regulation, arethe first areas that should be in-vestigated when a receiver is com-pletely dead. Then the technicianmust decide the priority of thesetests as symptoms are noted.

Low voltage and regulatorA conventional 4 -diode bridge

rectifies the 120Vac line voltageand filters the output with onelarge capacitor C518A (Figure 1).This is the unregulated supply,

measuring + 158V in normaloperation, that supplies all powerto the receiver. If the receiver is inshutdown mode, it is the only onehaving a do voltage (slightly higherthan normal).

However, the + 158V supply fur-nishes no power directly to any cir-cuit except the SCR513 regulator.The + 112V regulator outputdirectly powers the start-up cir-cuit, horizontal driver and outputtransistors and nothing else.Power from the horizontal -outputtransistor to the flyback is rec-tified, filtered and used for manylow -voltage supplies. Withoutvoltage from the + 112Vregulator, nothing in the receiveroperates.

Regulation by SCR513 is ac-complished by varying the lengthof time during each horizontal cy-

A Wards model GGY16229A (Photofact 2170-2) has most components on one largecircuit board. In addition, nine transistors, several variable controls and other com-ponents are mounted on the circuit board that includes the picture -tube socket. Twotuners and other controls for the customer to adjust are on the color receiver's frontpanel. A large percentage of electronic failures originate in the horizontal -sweepsystem and low -voltage power supplies.

de that the SCR conducts powerfrom the + 158V supply to the+ 112V supply. Electronic Serv-icing and Technology has ana-lyzed regulators having the samebasic principles in several previousissues. Please refer to some ofthose articles if you would like amore detailed explanation. In all ofthese, a heavier load on theregulated supply (or a lower linevoltage) reduces the regulated sup-ply below + 112V and causes thecircuit to gate -on the SCR earlierin each horizontal cycle. Each cy-cle ends at the tip of the horizontalretrace pulse, so this allows the+ 158V supply to flow for a longerperiod of time, thus increasing the+ 112V supply voltage. A lighterload on the regulated supply allowsthe + 112V supply to rise abovethat value and the circuit gates -onthe SCR later in each horizontalcycle. Therefore, there is less timefor the + 158V supply to flow intoC518B, and the voltage decreasesto the correct + 112V.

Another benefit of the circuitthat is not readily apparent is theincrease of the + 112V supply fromrectification of all positive portionsof the pulse waveform that is atthe SCR anode. Remember the+ 158V is there too, which forcesmore of the waveform positive.Proof? Well, 112V is about 70.9%of the 158V source voltage. Ifgating the + 158 solely wasresponsible for the + 112V, theSCR would be gated -on about thesame 70.9% of the time. Instead,anyone with a scope and a currentprobe can prove the SCR currentflows only for 30% of the time;slightly higher with highbrightness. The same proof is ob-tained by interpreting correctlythe SCR513 anode waveform. Justvary the brightness from dark -to -


high brightness and notice whicharea of the waveform becomeswider with the need for morepower. Of course, it is the area justto the left of each negative -goingpulse. The rectification de voltageis added to the + 112V supply soSCR513 does not have to conduct70% of the time.

Rectifying horizontal sweepAlmost any desired de voltage

can be obtained by rectifyinghorizontal from the flyback andfiltering it in the usual way. Forexample, + 220V is needed for thecollector resistors of the 3 -coloroutput transistors (mounted on asmall board that includes thepicture -tube socket and severalother components). Diode SC527rectifies the positive pulses fromflyback pin 10, and the ripple isfiltered by C540 (Figure 2). Thecold end of the screen control isreturned to this supply, to preventthe screen voltage from being toolow at reduced settings.

Loss of the + 220V supply usual-ly is caused by failure of diodeSC527, so check it first. If the+ 220V supply is reduced to nearzero, this reduces the positivevoltages at the three CRTcathodes. Therefore, the cathodesand grid have nearly the same devoltage, thus increasing thebrightness. In most cases, the pic-ture will be too bright and exhibitretrace lines.

For all brightness problems,check the CRT socket voltagesagainst the ones shown inPhotofact. Then work back fromthere through screen circuit, gridcircuit or cathode circuits.

Other important voltagesFigure 3 shows how diode SC530

and filter capacitor C540 produce+ 25V that is used for a few stagesand then reduced by a seriesresistor, a series resistor plus azener diode, a regulator transistor,an inductance, and, finally, an-other zener diode to form seven ad-ditional lower voltages from theoriginal + 25V supply (check thePhotofact 2170-2, page 35, powersupply for details). Only two sup-plies taken from the + 25V sourceare shown in Figure 3. Each sup-ply should be tested for voltageseparately. It is possible for a con-

120VAC

FS500 L500ON VOLUME R500

4A SW500de 2.?

A SHORT FROM AC TO GROUNDIN THE TUNER CAUSED FUSE,RESISTOR AND DIODE DAMAGE

SC500 j SC503 =

SC506i5C5091

R52913.9ISM

PART 24

OF T402FLYBACK z2

HORIZPULSES

.15BV

R527 C525330 .0069

SCR513A i1 K

G

C51BBi22pF

R51BB2.5K

__.15R 211000B. ADJ

SC512 GIVES A START-UP PULSE.3 TRANSISTORS DETERMINE 5CR513.5

CONDUCTION TIME.

CS1BA.+158VSUPPLY

75°P UNREGULATEDREGULATED

.112VSOURCEREGULATED

Figure 1. One side of the ac line voltage first passes through the 4A FS500 fuse, theL500 line filter and then reaches the on/off switch SW500. From SW500, the ac powerpasses through current -limiting resistor R500 and reaches its destination: one acend of the bridge rectifier (with four identical diodes). The other side of the ac linegoes only through the other winding of the L500 line filter and is connected to theother ac end of the bridge. The remaining two diode anodes are grounded, while thetwo cathodes of the bridge produce the B + voltage that is made peak reading andfiltered by capacitor C518A. Output of C518A is the unregulated + 158V supply,which is sent only to the regulator SCR513 and its timing circuit. During normaloperation, the + 158V passes through 3.9Q R529 and the pins -22 to 24 flyback wind-ing to the SCR513 anode. Therefore, a mixture of + 158V and negative -goinghorizontal -frequency pulses are present at the SCR513 anode simultaneously.Gating -on of SCR513 passes some + 158V to C518B, while the pulses turn off theSCR512 condition, regulating the + 112V source. But something needs to start upthe + 112V supply (even before the horizontal starts). Here are the steps. The first cir-cuit to begin working is the bridge rectifier and C518A (with what will be + 158V atcompletion). At turn -on, this C518A voltage is increasing rapidly and it passes apoint where zener diode SC512 conducts dc power that is sent to the SCR513 gate.Therefore, SCR513 conducts much of the + 158V into the + 112V line. Butsimultaneously, some of this same + 112V -type voltage passes through R421 (shownin the Figure 10 shut -down schematic), then is clamped to about +8V by zenerSC403, passes to the Q400 base (Q400 has collector voltage from the same + 112Vsource) so the emitter follows whatever the base does, and the emitter voltage issent to IC700 pin 9 as B+for the horizontal oscillator. All three horizontal stages(oscillator, driver and output) now have some B + and the horizontal system beginsto operate. Meanwhile back at the SCR513 regulator, the negative anode pulses havemade the SCR non-conductive during retrace of each horizontal cycle, while theother flyback pulses that are applied to the timing circuit have given the operation astandard, so variations of the + 112V source determine when during each cycle theSCR513 is gated into conduction to replenish the charge in C518B. Start-up now isover, and the operation is normal.

siderable overload to reduce one ofthe derived supply voltageswithout reducing the parent + 25Vsource very much.

Incidentally, the + 21.6V sourceis CircuiTrace 13 that feeds thevertical -output transistor, whilethe + 20.4V source is CircuiTrace11 that supplies the main voltagefor the IC102 sound IC. Also, thesound volume control obtainspower from + 23.8V at Cir-cuiTrace 5.

As an example of the manystages and circuits that are af-fected when a supply voltage fails,

the + 23.8V supply is formed byeither a diode or a 4.712 resistorthat brings in the +25V power,while the + 23.8V supply is filteredby C164, a 1,000µF, electrolyticthat filters and gives some voltageregulation. All these stages anddevices are supplied directly bythis + 23.8V source identified inthe Photofact as CircuiTrace 5: sync -separator transistor; vertical sync amplifier tran-sistor; AGC for the VHF tuner; first video amplifier transistor; second video amplifier;


PART OF T402FLYBACK 10 SC527

o

:1_1

11C5

C541I

0 .00221 C540

12 1 -1o

USED FOR THE COLOR OUTPUT TRANSISTORS.AND CONNECTED TO THE SCREEN GRID RESISTORS.

150µFY

+220V8 BOOST

Figure 2. In this Wards television, only two power supplies are made by rectifyingsignals from the flyback transformer. The + 220V boost supply furnishes collectorvoltage for the color -output transistors and the output regulators. It was oneselected to be monitored by the shut -down sensors.

Figure 3. The only other flyback -voltage rectified supply is the + 25V source. Sevenother supplies are taken from the + 25V source by using dropping resistors, zenerdiodes, transistor voltage stabilizers and many filter capacitors. If the + 25V sourcehas a defect and produces zero voltage, the other seven sources also each have zerovoltage.

Arrows point to several large high -wattage resistors that are mounted high above thecircuit board by rivets or pins that also serve as connections. This helps preventcharred or burned areas on the circuit board.

IC900 video/chroma IC; IC602 chroma demodulator; Q903 video back-seat videodriver; Q904 video driver; and contrast, sharpness, brightnessand sound controls.

There may be others as well, butthese serve to illustrate the pointthat failure of a key low -voltagesupply such as the + 25V or+ 23.8V can have widespreadsymptoms and problems.

As shown in the photograph,lower left, many smaller com-ponents of these low -voltage sup-plies are located near the chassis'front. C518 is the large metalcapacitor at the upper left in thephotograph, while the Q303 ver-tical output transistor is mountedon the large heat sink (just to theright of center). Notice thatseveral large, high -wattageresistors are mounted about aninch above the board by longstandoffs.

Checking LV power circuitsIf the 4A FS500 was blown when

the Wards television was received,and the replacement 4A fuse blewimmediately at turn -on, the firststep is testing all four bridge rec-tifiers, particularly SC500 andSC506, for shorts or seriousleakages. Any of the bridge rec-tifiers (Figure 1) can becomeshorted by power -line surges orthe secondary effects of lightningstrikes. Surge -current -limiterresistor R500 can become open orhave a changed resistance fromthese transients that must travelthrough it to reach the diodes andC518A.

Don't forget the possibility of ex-cessive ac line voltage, either tem-porary or permanent. I could findnothing wrong with one suchtelevision that blew fuse anddiodes at least once a week. It wason the fourth set of bridge diodesthat I checked the line voltage andfound if to be 136Vac! No morefuses or diodes blew after the linevoltage was reduced by the powercompany.

If all else fails, and one diodeshorts every week or two, replaceall four diodes with 3A types ofhigh reverse -voltage rating.

Unusual short circuitAlthough leaky bridge diodes

SCR500 and SCR506 had been


replaced, the 4A fuse continued toblow at turn -on. R500 was found tobe open, and was replaced. Alldiodes were checked again in -circuit (Figure 1) with SCR506testing a virtual short. But afterSCR506 was removed from the cir-cuit, it tested normal leakage. Nowa dead short was measured acrossthe terminals where SC506 hadbeen connected by soldering. C509(the 0.001 capacitor paralleledacross the diode) had no leakagewhen one end was disconnected.

In other words, one side of the acline was grounded to the receiverground, but nothing was defective.After several minutes tracingwires on the Photofact schematic,I removed the volume -control plugfrom the chassis and the short wasgone. That isolated the 120Vacshort -to -ground as somewhere inthe tuner assembly. Two smallneon bulbs are used to indicateUHF or VHF operation. A 33k0resistor at each neon bulb limitsthe current when the 120Vac is ap-plied to the bulb. One of the smallswitching dial -light components(SW506) on the rear of the VHFtuner was touching the tunershield (ground). This shorted oneside of the 120Vac line at a pointshown by an arrow and a brief ex-planation in the Figure 1 sche-matic. Moving the 120V connec-tion a safe distance from theground and adding some tape foradded protection stopped theground. The reinstallation of C509and diode SC506 and reinsertionof the volume -control plugrestored normal operation.

Checking the regulatorFour simple dc -voltage measure-

ments will give you more usable in-formation than will a dozen othertests made at random or with aninappropriate instrument. Thosefour points are: 1.) the + 158V out-put of the bridge rectifier; 2.) theanode of SCR513 (Figure 1); 3.)the cathode of SCR513 or otherconvenient source of the regulated+ 112V source; 4.) the Q402(horizontal -output transistor) col-lector (case).

Little variation from the stan-dard + 158V should be expected. Ifthe load is very light, the voltagemight rise to almost + 169V, butthat is unusual. If it is significantlylower then + 158V, and there is nosign of an overload, perhaps

1 . 6VPPHORIZSYNC

Figure 4. SCR's can be tested with fair accuracy with a high -power ohmmeter, asshown by the chart. The meter is placed where the typical readings are shown. The+ and - refers to the polarity of the ohmmeter leads. (If you are not certain,measure the voltage and polarity by using a voltmeter.)

1.4VPPHORIZ

SAWTEETH

NI C726.047

14

R442

-1(100KHORIZ

C436PULSES

.022 =

1C700 HORIZ/VERT B

COUNTDOWN

+8.1V

5 !+5.7V

+1.2V

736 R738 XT700; 2000 390

C722130pFj 503KHz 726

5VPPC004=

560102F

SC7o6 = I 7

9+8.6V TO BASE 00401 HORIZ

R742 DRIVER1000

+25V

NOTE: OSC START-UP DC VOLTAGEIS BROUGHT TO PIN 9.

FROMSHUT -DOWN

Figure 5. Important waveforms and voltages of IC700 are shown here. Horizontallocking requires two signals: horizontal sync (at pin 14); and horizontal sawteeth (atpin 1). Pins 4, 5 and 6 are used for the 503.5kHz oscillator that is divided down forhorizontal and vertical sweep frequencies. Pin 9 of IC700 is the B + input which isused with a dc voltage brought In during start-up. Normal operation supplies pin 9through SC706 and R726. Shut -down is initiated when the pin 9 voltage is drained outrapidly. Base signal for 0401 driver comes from pin 8.


C518A is open or partially open.Virtually the entire + 158V

should be expected at the SCR513anode. If SCR513 is not conduct-ing, they should be identical. Anappropriate anode do voltageproves the flyback pin 22 to 24winding is not open. Neither isR529 (3.9(l) open, nor is theassociated wiring. Of course, if the+ 158V supply has normal dovoltage while the SCR anode hasnone, the open component must befound and repaired before you canproceed. An open there might bethe only defect. Remember, R529is a 15W resistor that operatesquite warm in normal service.

If the SCR513 cathode has a dovoltage that is just a few volts

above or below the desired + 112V,perhaps the R521 B+ adjustmentcontrol needs proper rotationwhile reading the + 112V supply.Otherwise, the drain on the supplymight be too high or unusually low,or components in the 3 -transistortiming circuit might be defective.Voltage readings alternated withresistance readings usually willfind the bad component or tran-sistor in the timing circuits.

There is one minor warning:Some do voltage (up to + 158V)can be measured at the + 112Vsupply, even when SCR513 hasbeen removed. That's becauselOk2 2W R515 is connected be-tween + 158V and + 112V source.Obviously, such a high value resis-

Location of IC700 is pointed out by arrow. IC700 is mounted in a socket, whichsimplifies the replacement. Another arrow identifies the FS500 4A line fuse.

tor cannot operate the horizontal -sweep system. And if the + 158V isnormal but the + 112V is nearzero, the resistor will burn to acrisp. Watch out for it.

A good time to give the SCR513a resistance check is while it is outof the chassis, as shown in Figure4. Of course, when you want toforce a transistor, diode or SCRjunction to conduct (necessaryhere for the gate tests), be sure theohmmeter has 1.5V or higheracross the probes. In other words,use a high -power ohmmeter not alow -power one designed to keepjunctions from conducting.

Horizontal oscillator and driverPins 4, 5 and 6 of IC700 (Figure

5) are for the horizontal oscillatorthat operates at 503.5kHz with in-ternal dividers to provide horizon-tal and vertical drive frequencies.Of course, locking is performed atthe usual 15,734.4Hz frequency byhorizontal sync at pin 14 vs. asawtooth filtered from horizontal -sweep pulses and delivered to pin1. Proper locking is not possiblewithout both these signals.Horizontal frequency long -duty -cycle pulses (near square waves)for the base of Q401, the horizon-tal -driver transistor, leave IC700at pin 8.

Pin 9 wiring also is shown. Atfirst, pin 7 seems to have no func-tion except bringing B + from the+ 25V supply to the internaloscillator and dividers. However,pin 9 also is used for start-up of theoscillator (remember the + 25Vsupply is dead until after start-up),and it is essential for shutdown.Refer to Figure 7, page 18, forthose two functions.

SC706 appears to do nothingbecause the + 25V supply forwardbiases it, and it passes the voltageon to pin 9. But SC706 has a vitalswitching function. When the fee-ble start-up dc voltage comes in topin 9, the + 25V supply voltage iszero. Therefore, SC706 is reversebiased, which disconnects all theheavy + 25V supply load. It doesnot decrease the small start-upvoltage, so all of it goes to pin 9and IC700.

Pin 9 of IC700, the collector ofQ401 driver and the Q402 outputcollector all receive start-upvoltage at the same time. Thehorizontal -sweep system beginsoperation with these three stages


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Circle (6) on Reply CardFebruary 1986 Electronic Servicing & Technology 17

FROM 1C700PIN 8

0401

R74622

`73200z R- 470

0402HORIZ DRIVER HORIZ OUTPUT

7400R46

.45V .41v

C448.0047

R463

+69V 3300

R46747

C457.015

TO COLLECTOR OF 0400 R460 F5501HORIZ OSCILLATOR START-UP 1000 2A

112V

T402FL YBA C!

Figure 6. Although the circuit details and component values vary from one model toanother, the driver and horizontal output stage of one color receiver is very similar tomany others. So it is here. The FS501 2A fuse is a plug-in type that makes replace-ment easy. Or it can be removed to eliminate B + from the Q402 collector duringtests. IF C467 (.015µF) becomes open, the high voltage will increase greatly, causinashutdown. An open C456 (0.001µF in parallel with C457) also increases the highvoltage, but not very much. Every time you test a horizontal output transistor, alsotest the damper diode (SC415 in this case). Check it for forward voltage drop andwith reverse voltage for leakage. Remember that a damper diode must pass as muchcurrent in the negative direction as the output transistor does in the positive direc-tion. If there is no damper, or it is open, the collector/base junction of the output tran-sistor must pass the negative current in addition to its normal positive current func-tion. That is why a missing damper results in a delayed failure of the horizontal -output transistor.

operating weakly; then the powerincreases rapidly until the systemhas full power and can supply alldeflection, HV, and flyback powerthat is rectified to produce low -voltage supplies (photo, page 14).

Driver and output stagesConventional is the best word to

describe the driver and horizontal -output circuitry. Not all receivershave a fuse for the output tran-sistor and its flyback winding, asthis one does. Having a convenientway to disconnect the horizontaloutput collector from B + savestime with some tests (schematic inFigure 6).

Voltage for the Q400 collectorwas taken from R460 (collectorvoltage -dropping resistor for thehorizontal -driver transistor) as aneasy way to obtain a de voltage ofless than + 70V for Q400. There isno signal connection there.

Start-up and shutdown circuitsAn old saying wryly states, "The

+220V

SC405

+112V

R450

SC406123V

C44071.0022

SC409

CIRCUITS ON THIS SIDE R451ARE FOR SENSING EXCESSIVE 5200

HV 8 CLOSING SWITCHSCR412

R4483900

C44247NF`T'

SCR412SHUTDOWN

OV G

K

A

R42118K

SC4038V

+69V FROMHORIZ DRIVER8+ SUPPLY

0400START-UP

.8.2V

SC4040400 HAS TWO FUNCTIONS. Ii

8.6V GIVES START-UP DCV FOR THEHORIZ OSCILLATOR AND ITCONDUCTS DURING SHUT -DOWNTO KILL THE HORIZ SWEE.'

TO IC700 PIN 9

Figure 7. When the television is turned on, a start-up circuit in the regulator provides some B + voltage to the + 112V line. Thatvoltage is received by R421, in this schematic, and is sent to the 0400 base. If the voltage is larger than + 8V, the zener diodeSC403 regulates the 0400 base voltage to about +8V (8.2V in the sample). The Q400 collector has voltage from the + 112V linealso, so Q400 acts as an emitter follower. Whatever voltage the base has is duplicated (minus 0.7V) by the emitter. If the base has+ 8.2V, then the emitter produces + 7.5V which is sent to the IC700 pin 9. Although slightly less than the normal pin 9 voltage, itis sufficient to start the horizontal oscillator and its dividers. During this time, diode SC706 is reverse biased (there is no + 25Vsupply) and disconnects the large + 25V -supply load. The other two horizontal stages also have voltage from whatever start-upvoltage is on the + 112V line; therefore, the horizontal sweep begins to operate. The Q400 base is clamped to + 8.2V by the zener,while the emitter is connected to IC700 pin 9 where the voltage is + 8.6V. Q400 is reverse biased and inactive during this time ofnormal operation. SC706 becomes forward biased and operates pin 9 from the + 25V supply through R726. Start-up is over.Voltage sensing of the + 112V source is performed by 123V zener diode SC409. Voltage sensing of the + 220V supply is ac-complished by adding 123V zener diode SC406 to the previous SC409. If either supply exceeds the zener voltage rating, the zenerwill conduct voltage to R448 and R451. R451 is a low value to reduce the false alarms. R448 and C442 form a low-pass filter to in-tegrate erratic voltages, while C442 is storage for the dc voltages. Because the SCR412 cathode is grounded, a positive voltageof around 1V will gate SCR412 into conduction. This conduction grounds any positive voltage that is at the anode. Notice thatthe anode is connected to the SC403 zener mentioned previously and to one end of R421 that brings in + 112V to the zener. Also,the anode connects to 0400 base (which has no significance here) and the cathode of SC404 (which is important). Assume thatan overvoltage at a sensor has gated -on SCR412, SC404's cathode is grounded through the SCR anode while SC404's anode isconnected to IC700 pin 9. Therefore, the pin 9 power flows through SC404, through the SCR412 and to ground. Without B+, theoscillator and dividers stop working, and a split second later the horizontal sweep is totally dead. This is shutdown. Wait aminute or two for C518A and C442 to completely discharge, and start-up can be initiated again. If the cause of the shutdown hasbeen repaired, the color received will operate normally.


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- THE TABLESARE NOWTURNED 1985

1970 "Timesbegan to _et

tough"

1975

1980

1986

"The tablesare turned"

Diehl released

Mark IV Diagnostic Computer

Diehl began publishing Service Literature

"Shut down circuits made things even worse"

1986PROMISES

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-FOR TECHNICIANS -

IN THE PAST:We've all seen it happen. A piece ofequipment comes in for repair (deadon arrival). In the process of tryingto get it to power up, some halfdozen or so components "selfdestruct", and the customer nolonger wants it repaired.Furthermore, they don't even wantit back: Nor do they want to pay forthe time it took you to prepare theestimate.

A few days later, you see this samecustomer at the local discount chainstore buying a replacement unit forless than your wholesale price.

Well, unless that chain store is

prepared to give everyone a 60%discount (off their advertised price),things are about to change - - -.

Particularly, the labor costs ofrepairing electronic equipment thatfrequently develops low voltagepower supply problems. Orproblems in other circuits thatultimately show up as symptomsthat would normally lead even agood technician to "suspect" lowvoltage power supply problems.

The main problem has been pureand simple. The bench time requiredto complete repairs on mostelectronic equipment has madetoday's service shops totally non-competitive with the replacementcost of the same piece of equipmentat the local discount chain. And,non-competitive with thecontinually lower costs ofpurchasing a brand new unit.

The main culprit is, that it takesmore and more time to isolate thestage or circuit that has failed, thanit does to actually complete repairsonce isolation has been achieved. Inthe meantime, today's technologyoffers more and more"opportunities" that causeadditional components to selfdestruct while you are attempting toisolate the actual stage or circuitthat has failed. If you're not really

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careful, its pretty easy to make amajor service problem out of whatstarted out as a very minor repairjob, with regards to the number ofnew parts that will be required, andthe amount of time that will berequired to replace them.

INSTEAD OF THE ABOVE,IMAGINE THIS:

A home stereo amp or similar pieceof equipment shows up at yourbench for repair. Without eventaking the back off, you plug it intoa computer. The computer tells you(1) if any shorts exist in the unit; (2)if so, what type of a short exists.(i.e. is it a shorted LV rectifier, ashorted output transistor, a shorteddriver transistor, a shorted pre -amp,etc., etc.). The computer has such aneffective current limiting featurethat it will virtually not permit achain of components to selfdestruct. If on the other hand, thecircuit under test is open, thecomputer lights an "open" lightand tells you so. If the currentconsumption is normal, it also tellsyou that, with a "normal" light. Ifthe current consumption is low, thebar graph on the computer lets youknow.

This new concept oftroubleshooting all but eliminatesthe possibility of spending tedious

Continued on Page 43

Arrows with identifying names show the horizontal -output transistor that is mountedon a large heat sink on the circuit board and other components that have been men-tioned. To remove Q402 for external testing, remove two metal screws then unsolderthe emitter and bias terminals from the board wiring.

headlines give, but the fine printtakes away" in regard to contractsand policies. The Figure 7 explana-tion below the schematic has an er-ror when it says Q400 conductsduring shutdown to kill thehorizontal sweep. Actually, theIC700 pin 9 B + flows throughdiode SC404 and then throughSCR412 to ground (when the SCRis gated -on) to accomplish shut-down. Follow the path on theschematic.

None of the safety circuits invarious models actually check thedo high voltage directly. But thisWards receiver does the next bestthing. The + 220V supply ismonitored by the shutdown circuit.And that is good because this+ 220V is rectified from positive -going horizontal pulses (the samewaveform as the ac high -voltagebefore rectification). Therefore,the + 220V supply should rise andfall in step with the high voltage.An excessive + 112V regulatedsource can cause much componentdamage and generate dangerousX-rays if it rises too high;therefore, it also is monitored bythe shutdown circuit. Excessivevoltage of either or both supplieswill gate -on the SCR and produce

shutdown as it eliminates allhorizontal sweep and all do powerrectified from the sweep power.The symptoms are: no sound, noraster and usually no voltages ex-cept the + 158V supply.

Most shutdown circuits have alatching effect to prevent thehorizontal sweep from starting upagain spontaneously after a fewseconds. The Wards shutdown cir-cuit (Figure 7) has two latches.One is SCR412. After any SCR isgated into anode conduction, theconduction will continue until thecurrent drops below a certainsmall value before it becomes anopen circuit again. After the SCRconduction has removed the B +from pin 9 and stopped thehorizontal oscillator (and with itthe horizontal -sweep system),there might be some small voltageremaining in the + 112V supplythat through R421 continues tosupply current to the SCR412anode. Only when the currentreaches the de -latching point canthe circuit undergo start-up.

The other latch is that start-upcannot occur until filter capacitorC518A is discharged to almost OV.Wait at least a minute or twobefore trying start-up after the

horizontal -sweep has been stop-ped. Remember, the horizontal -sweep system will not restartitself; it must go through the for-mal start-up sequence. This can befrustrating when you are checkingfor an intermittent in thehorizontal -sweep circuit. Each in-termittently dead sweep requires anew start-up.

Locations of several importantcomponents that already havebeen discussed are shown by ar-rows in the photograph on page20. To remove Q402 horizontal -

output transistor for externaltesting, remove two metal screwsthat hold the transistor case to theheat sink. Then unsolder base andemitter terminals from the circuitboard wiring and lift the transistorup and out.

Practical servicing tipsThe interconnections between

regulator and horizontal sweepplus the addition of start-up andshutdown circuits admittedly com-plicate logical troubleshooting.Technicians who like to livedangerously merely can discon-nect the shutdown circuit, andtake a chance that nothing expen-sive will be damaged by the ex-cessive high -voltage arc. Ofcourse, the shutdown circuitrymight have become defective.Perhaps we need a backup sensorfot the shutdown circuit!

Disabling the shutdown circuit-Connect the gate and cathode ofSCR412 together with a firm con-nection (remember the gate is lowimpedance) and have a HV meterprobe touching the picture -tubeanode as the receiver power isswitched on. If the sound comeson, the meter reads no higher than29kV, and then the picture ap-pears to be normal, the defectmust be in the shutdown circuit.First measure the + 220V sourceand the + 112V regulated supply.If both supplies are correct, checkfor do voltage between SC406 andSC409. There should be + 112V.Then check at the output of 123Vzener SC409 (at the junction ofR448 and R451) for any do voltage.There should be none. Measure theresistance of 82000 R451. If it isopen, the circuit will be very sen-sitive to the slightest leakages inSC406 and SC409 and to any rapidchanges in the two source


voltages. Make certain C442 is notopen. Remove the gate -to -cathodeshort and measure the gatevoltage. It should be zero. One ormore of these tests should have un-covered something wrong ordefective. And replacing the defec-tive part or parts should stop theunwanted shutdown. Remove alltemporary wires used duringtesting.

Finding excessive high voltage -There are only a few defectsthat can increase the high volt-age enough to be dangerous. Sometechnicians (without thinkingvery deeply) will say, "Shortedturns in the primary winding." Ofcourse, fewer primary turns givethe effect of more secondaryturns. However, the shorted turnswould reduce the primary induc-tance to virtually zero and place ahuge overload on the horizontal -output transistor. The usual causeof excessive high voltage is anopen retrace -tuning capacitor.There are two in the Wardschassis. The most important one isC457 (0.015µF as shown in Figure6) and the other is 0.001µF C456.Both are connected between col-lector and emitter (grounded) ofQ402. Smaller capacitance valuesnarrow the HV pulses and increasethe amplitude, while larger valuesbroaden the pulses and decreasethe amplitude. Replace only withfactory -supplied capacitors or withreplacements manufactured foruse with pulse circuits. Do not use"garden" varieties of cheapreplacements.

Checking the horizontal outputstage-Our intent is to drive theoutput stage from test equipment,thus allowing the oscillator to bestudied in detail. But first the out-put stage must be known to be ingood condition. Check Q402 forshorts and leakages in -circuit. Isthere a resistance reading fromthe Q402 case to both ends of the2A FS501 fuse? If so the fuse andflyback winding are not open.

Inject a horizontal signal froman analyst to the base and emitterof Q402. Also, add a clip lead fromground to the Q401 driver base,just in case the oscillator comes tolife. Check the + 25V source to becertain the substituted drivewaveform is working correctly.

If a raster or out -of -lock picturecan be seen, begin testing the

horizontal oscillator circuit. Pin 9should have about + 8.6V, pin 4should have the proper countdownoscillator waveform, and thehorizontal drive waveform shouldbe at pin 8. If any waveforms areincorrect, check the do voltages.Remember the Q401 base is shortedfor the analyst test. If anywaveforms or do voltages are veryincorrect, replace IC700. Ex-perience has shown that replace-ment of Q402 and IC700 solvesmost problems.

But what about another receiverwith drive signal from the analystthat did not have high voltage?First, measure the do voltage at2A fuse FS501. If it is very low,the regulation is not operatingwithout the horizontal pulses.Check the output transistor andflyback as best you can, but if thetests are not conclusive, it mightbe necessary to obtain voltagetemporarily from the + 158V sup-ply. Power the ac through anisolation transformer and avariable -voltage transformer(these can be two items or one if ithas the correct specifications).Before applying ac power, connecta test lead from the + 158V supplyto the input side of FS501 (nearthe flyback). Now apply 85Vacfrom the variable transformer tothe television. This should supplyapproximately + 112V to the 2Afuse and the output transistor.

Remember the Q402 base signalis supplied by an external analyst.After the power has been on for aminute or two, turn it off and feelthe Q402 case. It should be cold tocool. If it is very warm, the suspectis the flyback. Check it for shortedturns or defective internal diodes(if you have the equipment). If theQ402 output is not too warm,prepare a HV meter and try theoperation without the yoke, or bet-ter yet, with the red yoke wiredisconnected. If the HV is in-creased, the yoke probably hasshorted turns. Defective flybacksoften will make popping or fryingsounds, and with the power off, abad one will feel very warm.

After the output alone has beenmade to operate smoothly with thetemporary power supply, then theanalyst should be removed, alltemporary jumpers and test leadsshould be removed and the per-formance should bechecked at 120Vac.v,

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Solder:The tin tie that binds

By Conrad Persson

Much has been written about thetremendous advances in elec-tronics: transistors, ICs, printedcircuit boards, microcomputers,LEDs, LCDs. It almost leaves youbreathless. One thing hasn'tchanged: When components arephysically and electrically con-nected into the circuit, it's usuallydone with a soft, low -meltingmetal alloy called solder.

Although solder and its use inelectronics haven't changedmaterially over the years, the sizeof the components and wiring thatsolder connects together, ingeneral, has been reduceddramatically. The susceptibility ofthese devices to damage from ex-cessive heat, electrostaticdischarge and physical stress hasincreased inversely. Therefore,soldering/desoldering techniqueshave changed.

Back in those earlier days whena component needed to bedesoldered, you yanked out the100W soldering gun and pouredthe heat to the joint while youpulled and poked at the wire withone of a variety of desolderingaids. If you removed the suspectcomponent from the circuit and itproved not to be the culprit, youcould solder it back in and continueby trial and error.

The rules have changed a greatdeal. In today's world of crowdedboards and delicate componentsand traces, you don't remove acomponent unless you're dead sureit has failed. When you do remove

We wish to thank the Electronic Industries Associa-tion, Consumer Electronics Group and Sony Corpora-tion of America. The information for this article wasadapted largely from the instructional videotapes"High Tech Soldering" produced by EIA/CEG and"Chip Component Replacement" produced by Sony.


a component, you use a small -tipsoldering iron, preferablytemperature controlled, and applyonly as much heat as is necessaryto melt the solder enough torelease the component.

The right soldering suppliesWhen you sit down at the service

bench, open up a modern con-sumer electronic product anddetermine that one of the circuitcomponents is at fault and willhave to be desoldered from the cir-cuit and replaced, you should havecertain materials available.

SolderSolder should be 0.015" (15

thousandths) wire solder with arosin core. It should be made ofvirgin tin and desilvered lead, andbe free from impurities such aszinc, aluminum, iron, copper, andcadmium. The lowest meltingsolder, and the one that yields thestrongest bond, is made with aratio of 63% tin and 37% lead, but60 tin/40 lead is nearly as good andis far less expensive. Most elec-tronic work is done with themoderately priced 60/40 solder.

Some manufacturers recom-mend silver solder for some work.Silver solder contains about 3%silver along with the lead and tin.Silver solder is recommendedwhen soldering such componentsas ceramic capacitors that havesilver -palladium fired -on conduc-tive surfaces. If straight tin/leadsolder were used to solder thesecomponents, the solder might ab-sorb some of the silver from thecomponent, causing a weak jointand poor adhesion. The smallamount of silver in the solderreduces the migration of the silver.

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A repair and rework center, such as this one offered by AP.E. provides facilitiesto completely repair all printed circuit board types: conventional, S -M, hybrid.

Silver solder is used in the samemanner as ordinary solder andperforms essentially the same ex-cept for a slightly higher meltingpoint.

This brings up an importantpoint: You should always have themanufacturer's literature on handwhen you're servicing a piece ofequipment. In the case of solderingcomponents, if the literature callsfor silver solder, use it. Otherwise60/40 should be fine.

FluxOrdinarily the rosin core of the

solder you'll be using will be ade-quate to clean oxide from the jointas you solder. In some cases, youmay need additional flux. It's not abad idea to have some high -qualityliquid rosin flux on hand. Rosin is anon-conductive, non -corrosive fluxand so is recommended for elec-tronic work.

CleanersRosin flux is sticky and will col-

lect dust, which will, in time, buildup and cause leakage. Cleaning offany excess flux will remove apotential cause of the units failinglater. Besides, a repaired board ismuch easier to inspect if it's beencleaned. You should have a cleanerof a type recommended by elec-tronics manufacturers that canclean rosin, oils and general dirt.

The soldering ironObviously, the most important

tool for soldering and desolderingis the soldering iron. If the volumeof soldering you do is small, youmight want to use a simple iron

along with various aids andmaterials. Or, if you will be doing alot of soldering and desoldering,you might want to consider a com-plete PC board rework station con-sisting of a soldering tool, a desold-ering tool, vacuum removal ofsolder and more. Whatever type oftool you select, it should be pencil -size unit between lOW and 50W,and should be temperature con-trolled in order to avoid damage tocomponents and circuit traces. Anadded feature you might want tohave is a reduced -current modeiron: That's one which uses a low-ered current when it's idle, therebyreducing energy usage and pro-longing the life of the element.

In these days of integrated cir-cuits with the attendant danger ofzapping a MOS device with staticelectric discharge, it's recommend-

ed that your soldering tools begrounded in order to drain off anycharge as it accumulates. Solder-ing tools that are grounded aregrounded through a resistance of250,000(1 to 1M(1 to drain away thestatic charge without posing ashock hazard to the user.

Other toolsThe need for some of the tools to

aid soldering and desoldering isobvious. For example, you'll wantto have some long -nose pliers,some cutters and maybe an arrayof picks and other desolderingaids. With components rapidlyshrinking in size, you'll find thattweezers in a variety of sizes willbe very helpful.

It also is handy to have a thirdhand available when you're work-ing on PC boards. Some kind offixture to hold the board will be agreat help while you hold thesoldering iron in one hand and apair of tweezers or a coil of solderin the other.

The most important tool of all,might just be a good magnifyinglamp. After all, we're dealing withICs so small that a good sneeze willsend them flying into oblivion andcircuit traces so fine they're almostinvisible. When you've finishedyour repair on a defective board,and you need to look closely to besure you don't have any solderbridges or other technician -induced problems, you're going to

For PC board soldering and desolder-ing, you'll probably want to use atleast a temperature -controlledsoldering station, such as theEC3000 shown here, by Weller.


want plenty of light, and somemagnification.

Delsoldering toolsand supplies

The whole idea of desoldering isto remove the component with theleast possible application of heat,the least possible damage to thePC board, and the least cost.Again, the issue of cost will bedetermined by the volume ofsoldering and desoldering you do.If you never will do a very highvolume of this type of work, thenthe lowest possible investment incapital equipment is probably thebest approach. On the other hand,if you're going to be doing boardafter board, then the mosteconomical method probably willbe the the one that lets you workthe fastest regardless of the cost ofthe equipment.

Desoldering braidFor low volume soldering ap-

plications, desoldering braid isprobably one of the few thingsother than a good soldering ironthat you'll need. This material isnothing more than fine copperwire formed into a braided wire,impregnated with rosin flux androlled up into a coil for easy handl-ing. You simply place the braid orwick against the joint to bedesoldered, and apply the solder-ing iron. The heat from the solder-ing iron melts the solder, andcapillary action wicks the meltedsolder into the braid. Besides theadvantage of low investment, thecapillary action acts at relativelylow temperature, and the presenceof the braid between the iron andthe PC boards helps to keep thedelicate circuit traces from beingdamaged.

Desoldering braid is available ina variety of widths, and the size ofbraid used for a particular jobshould be selected to be just wideenough to cover the joint, or land,being worked on. And you may getbraid either plated or unplated.The unplated absorbs more solderper area of wick, but the plated hasa longer shelf life because theplating material doesn't oxidize asreadily as copper.

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A repair and rework system can provide you with just about any combinationof PC board repair capabilities you can imagine, as shown here.

Suction devicesAnother approach to eliminating

solder from a joint is to melt thesolder, and while it's still molten,suck it out. There are basically twosimple, inexpensive ways to dothis. The cheapest is to use a suc-tion bulb device that has a Teflonor other heat resistant nozzle at-tached: Melt the solder, squeezethe bulb, apply the nozzle tip to themelted solder and release the bulbquickly. With any luck, the meltedsolder will be sucked through thenozzle and wind up as a tiny ball ofsolidified solder in the bulb.

Another manual solder -suckingdevice is the spring -loadedplunger. With this device, youpress the plunger against the forceof a spring within a cylinder. Youapply the nozzle of this tool againstthe molten solder of the joint beingworked on and press the trigger.This releases the spring, theplunger slides up into the cylinder,creating a vacuum at the nozzle tipand again, with a little luck, the

solder ends up in the cylinder.These two devices have the ad-

vantage of being low cost. Alsoyou can do quite a number ofsolder joints with them before theyneed to be cleaned out.

The solder/desolder stationIf you're going to be doing a

large volume of PC board solder-ing and desoldering day after day,you'll be more concerned with pro-duction than with economy ofequipment. If you are in thiscategory, you might consider acomplete solder/desolder station.These can cost from a few hundredto a few thousand dollars, sothey're obviously not for everyone.But one of these units, dependingon your selection, can doeverything from soldering anddesoldering conventional com-ponents to soldering and desolder-ing surface -mount components, torepairing the printed circuit board.

Some of the options on one ofthese stations include having two,


or even more, heat producing unitson the same unit so you canvacuum-desolder with one unit andsolder with the other without hav-ing to change tips. You can get onewith a self-contained air pump togive you both vacuum and airunder pressure, or if you alreadyhave compressed air available, youcan buy a unit that's designed tointerface with your existing airsystem. You can opt for at-tachments that will let you stripwires thermally. You can have justabout anything you could possiblyneed to rework a PC board in oneof these units: Just bring money.

Skill: The most important toolThe EIA, in their high-tech

soldering/desoldering videotape,emphasize one thing above all, andit sure makes sense: The most im-portant tool of all is diagnosticskill. It may seem to have nothingto do with soldering, but lack ofdiagnostic skills may be thegreatest cause of component andboard damage resulting from at-tempted repair.

In the past, one of the most com-mon test methods was to replace asuspect part, then test the unit. Intimes past, the approach madesense. Today, however, most con-sumer electronic products consistof delicate components crowdedonto printed circuit boards withequally delicate circuit traces. Ifyou attempt to remove one ofthese components and it turns outthat there was no problem to startwith, there probably will be a prob-lem when you're finished. Underthe best of conditions, a trainedtechnician with the proper toolscauses stress to both the compo-nent and the board. If you tryreplacing components one at atime in an attempt to find thecause of the problem, you mightend up with a board that's beyondrepair.

In short: If you don't know whatthe problem is, don't shotgun it.

Turning on the heatOnce you're sure you've isolated

the problem to a component andyou're ready to replace it, then it'stime to use whatever method thatyour particular circumstances

have led you to choose. By now,almost everyone who handles asoldering iron has gained familiari-ty with replacing standard DIPICs, so this article won't addressthat. The challenge these days ishandling some of the newer, ex-tremely small devices, those withleads close together such assurface -mount devices.

In researching for this article, Ireviewed several videotapes, reada great deal of manufacturer'sliterature and found there are anumber of ways to go about solder-ing and desoldering some of thenew components. Depending uponyour particular situation and skills,one or another of the methodsmight work best for you. Severalalternatives will be presentedhere. You might want to experi-ment to determine which methodyou like.

Chip componentsChip components are tiny, and

they're soldered on the same sideof the PC board they're mountedon, but they're really not hard tohandle. Starting with 2 -terminaldevices, resistors and capacitors, amethod for removing chip com-ponents recommended by the EIAis to grasp the failed componentwith pliers or tweezers, melt thesolder at one end of the devicethen quickly apply the solderingiron to the other end of the compo-nent while applying a very gentle,twisting motion. Move the solder-ing iron back and forth betweenthe ends as necessary to reach apoint where both ends are moltenenough to lift the unit away.

This brings up a very importantconsideration for soldering anddesoldering of surface -mountdevices. In many cases, a drop ofadhesive was applied between thecomponent and the board duringthe manufacturing process to holdit in place while the board is masssoldered. This glue is specially for-mulated so that once it has cured,if a twisting force is applied, it willshatter and the devices can beseparated easily. Usually theadhesive is heat sensitive as well,and application of heat will softenit enough to remove a component.

Not all components on a board

will be glued down. In many cases,certain ICs or other componentswill be soldered manually after themass soldering of all of the othercomponents is complete. Becausethese devices do not have to beheld in place for a mass productionoperation, they do not need to beglued down.

Another approach to chip com-ponent removal was shown in asoldering/desoldering instruc-tional tape available from Sony.Using two soldering irons, you canplace one at each of the two joints,heat both simultaneously, and liftthe removed component away be-tween the irons.

Using either of these methods,you'll probably be left with someexcess solder on the lands. Ap-plication of a clean soldering ironmight be enough to remove all theexcess. If not, use solder wick or avacuum device along with heatfrom the iron to get rid of it.

Because resistors and capacitorsare relatively insensitive to heat,when you're readying the replace-ment device, you can make the jobeasier by preheating it to about150°F (you can do this by applyingheat from a hair dryer for abouttwo minutes) then loading one landwith solder. Place the prewarmedchip in position and apply thesoldering iron. When the first endhas solidified, apply heat andsolder to the other end to completethe repair.

If you find that you have re-moved a chip component from theboard that wasn't the problem (andthis really shouldn't be allowed tohappen), don't solder it back ontothe board. NEVER reuse a chipcomponent that has been removedfrom a PC board. If it wasn't com-pletely destroyed, its life probablyhas been significantly shortened; itlikely will be a cause of failure inthe future.

Chip transistorsYou can handle removal of chip

transistors much the same way asyou would 2 -terminal devices.Start with the side where there'sonly one terminal and melt thesolder connecting it to the circuit.When the solder is melted, careful-ly raise the terminal away from


the board. Then, applying heat toboth of the other terminals alter-nately, get both warm enough tomelt the solder and lift the devicefrom the board. Replacement of achip transistor may be performedin much the same manner asreplacement of a passive device,except do not preheat a semicon-ductor device.

Flat packs (chip ICs)Never remove one of these unless

you're dead SURE it's defective.With a flat pack, as with othercomponents, there are severalmethods to remove the device. Oneshown by the EIA on its trainingtape is to use solder braid toremove as much solder as possiblefrom each terminal, then, takingone terminal at a time, heat theterminal, and with a pick, gentlylift it from the land it's soldered to.When all terminals have beenlifted, remove the IC. If the device

A

One nonconventional method of remov-ing surface -mount devices from a PC boardis to run a length of non -kinking wire betweenthe body and the leads of the component, addheat from a hot-air station and pull the wire betweenleads and lands when the solder is molten. (Thismethod and the drawing were provided by Edsyn)

was glued down, it may benecessary to twist it to break theadhesive.

Another method of removingone of these multiterminal devicesis to use a special desoldering headfor your iron that will heat all theterminals at the same time. Ofcourse, you have to be careful tochoose one of the correct size for

the IC you'll be removing. Thereare special wire forms that youplace under the leads of the IC.

When you have heated all theleads, simply lift up on both thesoldering iron and the wire form atthe same time.

Still another method recom-mended by Edsyn, Inc. is to inserta length of 0.010" diameter pull

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wire (actually this is piano wire)under the legs of the IC, and, usinga hot air type of desoldering unit,blow warm air across the ter-minals until the solder melts. Aseach terminal becomes moltenenough, gently pull the wire be-tween the terminal and the PCboard land. This is sufficient tobreak the solder bond and make itpossible to remove the device.

The company also recommendsthis method in cases where you'realmost certain that a particulardevice is faulty, but the only wayto be sure is to disconnect one ofits terminals from the circuit. Withthis method, or using a pick, youcan lift one or two pins to isolatethose IC functions from the rest ofthe circuit for testing, without hav-ing to remove the IC from theboard.

Connecting the replacement ICHere's where you get to use that

bottle of liquid flux we recom-mended that you keep on hand.After you've removed the faileddevice and cleaned up any excesssolder, brush the lands with liquidflux. This does two things for you.First, because very little solder isneeded for each connection, theflux core might not be enough toproperly clean the joint. Second,the flux is sticky, and this will helphold the IC in place while yousolder it.

Once you have the IC in place,and after making sure it's properlyaligned with the PC board lands,solder down a couple of leads, thensolder the rest.

There appear to be at least twoschools of thought on soldering theleads of a flat pack. The EIAvideotape showed the techniciancarefully applying the soldering tipto each lead and touching thesolder wire to it, trying to avoidcausing any solder bridges. On theother hand, the Sony tape advisesyou to tack down the IC, then putsome solder on the tip of thesoldering iron and draw it slowlyacross the leads.

In both cases, an important stepis to inspect the final productcarefully to ensure that no solderbridges have occurred. In theevent that there are solder

Here is a list of the manufacturers and organizations thatprovided information on which this article is based:

Automated ProductionEquipment Corp.142 Peconic Ave.

Medford, NY 11763

Chemtronics, Inc.681 Old Willets Path

Hauppauge, NY 11788

Contact East7 Cypress Drive

Burlington, MA 01803

The Cooper GroupP.O. Box 30100

Raleigh, NC 27622

Edsyn Tools15958 Arminta St.

Van Nuys, CA 91406

GC Electronics400 S. Wyman St.Rockford, IL 61101

Pace, Inc.9893 Brewers Court

Laurel, MD 20707

Wahl ClipperSterling, IL 61081

Sony Corporation of AmericaSony Drive

Park Ridge, NJ 07656

Electronic Industries of America,Consumer Electronics Group

2001 Eye Street, N.W.Washington, D C 20006

bridges, it's no problem to get ridof them. Again, there are at leasttwo methods. The simplest is tomake sure that the soldering tip iswell tinned but free of excesssolder and draw it along the lengthof the gap between the leads fromthe body of the device outwards.The tip should pick up the excesssolder forming the bridge.Another method is to apply solderwick and the heat of the iron at thesolder bridge and absorb the ex-cess solder with the wick. Thisshould leave enough solder be-tween the leads and the lands toassure a good connection.

After experience with these twomethods, you already may haveselected the method that is bothcomfortable to use, and that youare confident will ensure a good,reliable solder joint every time.

For further studySoldering skill always has been a

determining factor in successfulbuilding or repairing electronic cir-cuits. Poor soldering techniquemay lead to cold solder joints orvoids that in time may lead tofailure. Sloppy soldering mayresult in short circuits that resultin the production of smoke wherethere should be none - at great ex-pense.

Today, soldering skill is of para-mount importance to technicians.We hope that this article has givenyou some guidelines for proper

soldering. If you will be doingmuch soldering of PC boards fromhigh-tech consumer electronicproducts, you would be well ad-vised to take advantage of instruc-tional videotapes, courses andother assistance offered by con-sumer electronic product manufac-turers, soldering equipmentmanufacturers, or organizationssuch as the EIA.

After having seen videotaped in-structions offered by EIA andSony, I can say that if I had to goout and repair a crowded, printedcircuit board, I would be a lot morecomfortable with the informationthe tapes gave me. If I were to ratethe two tapes for usefulness, I'dhave to give the EIA tape a slightedge, but the Sony minicoursecomes with a small PC board andsome surface -mount componentsto practice with. And practice -soldering on a board using com-ponents that are expendable isprobably a good idea before takinga chance with a $1,000 -plus VCRor video camera.

You might wish to contact themanufacturers and organizationslisted above in this article andask them what kind of informationand course material they haveavailable. Other consumer elec-tronics manufacturers also mayhave soldering/desoldering infor-mation for free. Check with yourfavorite manufacturer to find out.

OWL28 Electronic Servicing & Technology February 1986

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atic diagram designate the com

ponents In which safety is

of special significance. It Is recomm

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of those components.

Use of substitute replacem

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-m

ended in factory service information m

ay create shock, lire, excessive x-radiation or otherhazards.

This schem

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ent contains no user -serviceable parts.

The other portions of this schem

atic may be found on other P

rof ax pages.

Reprinted by perm

ission of General E

lectric Consum

er Electronics G

orpxratixnC

opyright 1986, Electronic S

ervicing & T

echnology, P.O

. Box 12801, O

verland Park, K

S 66212

Reprinted by perm

ission of Genera, E

lectric Consum

er Electronics C

nrporatlonC

opyright 1966, Electronic S

ervicing & T

echnology, P.O

. Box 12901, O

verland Park, K

S 68212

Moreonthetelephonetester

Editor's note: Letters and phonecalls from a number of readerspointed out that although thetelephone tester featured as a con-struction project in the November1985 issue of ES&T appeared to bea valuable piece of equipment, a fewkey pieces of information wereomitted.

We have contacted the article'sauthor, Joseph Szumowski; he pro-vided us with the following infor-mation.

The 7812 and 7805 are ICvoltage regulators with a V,N, Vourand ground lead. These are labeledon the package when you buythem, or you can check your ECGor SK substitution guide-itdepends on the case style you pur-chase. (See Figures 1 and 2.)

The diode in the power supplyis a 1A, 600PIV rectifier diode.Any general purpose rectifiershould do.

The resistor above the LED inthe schematic is 470f2, 1/2W.

Figure 1.

Figure 1. The pin numbers fortwo of the ICs-the 555 and the4001-were omitted on theschematic in the Novemberarticle. This is how the pins arelabeled.

IN7805

IN7812

Figure 2.

OUT

OUT

1 = INPUT2 = OUTPUT3 = GROUND

1 3 2

Figure 2. The functions of the pins onthe 7805 and the 7812 are as shownhere.

The value of the choke coil is


ICIIN PUT

TONE TEST

Q, 1

LEADS

9

RINGER TEST

D°DT SWITCH

Figure 3.

T1 4R UNIT UNDER TEST

X

NOTEYou can use a modular -type plugif you like (place it in -parallel).

Figure 3. Connect the tester to the telephone as shown here in order to perform tests.

MODULAR JACK

POWER ONLED

RING TESTSWITCH

(push-button)

ADD DPDT SWITCH HERE(as suggested)

Figure 4.

PLEXIGLASS PAINTEDWITH PATTERN(covering LEDS)

POWER ONIOFF

RING LED (GATE OF MOSFET)INDICATES THE INTERNAL RINGGENERATOR IS FUNCTIONING

Figure 4. Here's what the completed telephone testing unit looks like.


not critical; it is simply an induc-tive load for the MOSFET. I used a1H, 200mA filter choke coil.

The resistors from IC3 to theLEDs in the display are simplycurrent -limiting resistors to pro-tect the LEDs. I used what I hadavailable in my junk parts box. Us-ing 47012 resistors would providesufficient brightness (over 22051 or330(1 would be fine) and limitingprotection. The difference will bein the brightness of the LED.

The markings T and R on thejacks designate Tip and Ring,terms commonly used by thetelephone company (this is aholdover from the days of theoperator who connected calls withpatch plugs: The plugs have a con-nector at the tip, and the secondconnector is in the form of aring, corresponding to today'sstereo plugs). In the telephonesystem, these are connected to the

red and green wires, respectively.In most systems, the yellow andblack wires are not used for thetelephone function.

Note, though, that in sometelephones it may be necessary toconnect the yellow wire with thegreen wire to allow the ringer tooperate. In my experience this israre, and the only wires I con-nected were the green and red.

Testing procedure1.) Connect the telephone under

test to the T and R pins. (SeeFigure 3 for connections.)

2.) Place the DPDT switch in theringer test position and press theringer test button. NOTE: Don'tforget to set R17 (IC5) to the correctfrequency (20Hz). Another way toset it is to connect a known -goodtelephone and adjust R17 for prop-er ringing.

Tone Testing position. Be sure theleads are in proper polarity. If theleads are connected backwards,the telephone won't be damaged;the tone pad simply will not work.Again, use a known -goodtelephone and check R4 for theproper gain setting (IC amplifier).Depress a key on the tone keypadand observe Dl. Remember thatthis setting is important: If thegain of IC1 is not set properly, thedecoder (IC2) will not function.

The address of the company thatmakes the DTMF decoder is asfollows:

Teltone Corporation10801 120th St.Kirkland, WA 98033206-827-9626

3.) Now place the DPDT to the

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Repairingthe consumer

color video cameraPart 3

By Neil Heller

With few exceptions, color videocameras are almost 100% solid-state. These components haveproven to be reliable over manyyears of operation. The main com-ponent, the image pickup tube, is athermionic device and has aphotosensitive target. Excessivelight can cause image burn on thetarget faceplate. In addition, thecathode can become depleted. Forthese reasons, the life of thecamera is directly related to theoperating time of the tube and thecare taken to protect the tube fromdamage.

Changing tubes: when and whyAny attempt to replace the tube

should not be made without agreat deal of forethought. Tubechanges will require a completecamera realignment. Replacementtubes are expensive, and the costof labor can at times be more thanthe cost of the tube. The deter-mination to replace a camera tubecan be based on one of two factors:tube aging or tube damage.

Tube agingTube aging is the result of

diminished cathode emission.When this occurs, the dark currentincreases, accompanied by therelated symptoms of reduced con-trast, signal-to-noise ratio, resolu-tion and increased lag. The point

at which the tube is no longerusable is left up to the operator.Due to the high sensitivityspecifications and lack of stripefilter, 3 -tube color cameras havean advantage in operating life oversingle -tube cameras.

Deterioration of the targetfaceplate in a single -tube cameracauses loss of resolution of thestripe filter. When this occurs, thecamera loses its ability to producered and blue. The only signal leftyields green. This loss is notlimited to the faceplate. Dif-ferences in beam scanning also canbe caused by the yoke assembly.

Tube damageGood judgement and proper

handling are essential to prevent-ing costly repairs caused by tubedamage. The most common type oftube damage is usually caused byan inexperienced operator who,without thinking, points thecamera at the sun or a high con-trast scene. Concentrated lightdecreases the variable propertiesof the target to the point where itcan no longer respond to changinglight levels. Usually image burn isconfined to a spot rather than af-fecting the complete faceplate.There are myths that certain typesof tubes are not susceptible to thisproblem, but all types of targetsare subject to image burn. The

type of target material will deter-mine the degree of susceptibility.Image burn can occur even whenthe camera is not operational.Always remember to iris down andcap the camera lens when thecamera is not in use.

Don't make the mistake of con-fusing burn with dust. Image burnshows up as white spots due tophysical or chemical changes in thetarget material. Dust reduces theamount of light available to thetarget, so it shows up as a grayspot, which will vary in contrast asthe lens is opened and closed. Inaddition, because the dust particlelays on top of the target's focalplane, it will appear slightly out offocus. If you think you have a dustproblem, carefully clean the lensglass and optical faceplate with anon-abrasive tissue. If this methoddoesn't solve the problem, thenremove the tube from the yokeassembly and clean the targetfaceplate. Remember, removingthe tube means that the cameramust be readjusted in order toreturn it to operating condition.

Another cause of tube damagethat closely resembles burns is tubespotting. Never leave the camerain a position where it is resting onits lens. Because of the construc-tion of the image pickup tube, bitsof metallic dust have a tendency toadhere to the positive target


faceplate due to its positive poten-tial. These metal particles canalter the ability of the tube to pro-duce a proper picture. Therefore,it is advisable to avoid holding thecamera in any way that may allowgravity to foster this condition.Never hold the camera lens -down.If the camera is resting on atripod, leave it tilted up at a smallangle.

Finally, avoid high tempera-tures. It's wise to keep video equip-ment in a safe place however, leav-ing your camera in the back seat ofa car or in the trunk is a good wayto damage the tube. Temperaturesabove 104°F or 40°C can causechemical changes in the pickuptube, lowering the targetresistance. This can cause an im-age to burn more readily into thefaceplate.

Should image burn occur,endeavor to correct this conditionby defocusing your camera on a

well -lit, white background. Thismethod of rejuvenating the tube isoften used in B&W cameras.However, because of the operationof the color camera tube, the sen-sitivity may be reduced to a pointwhere it can no longer produce col-or, or the picture may be too noisyto be acceptable. If you want to trythis method, make sure that thelens opening is not greater than f4.Running your camera this way forapproximately one to two hoursshould help to burn out the image.

Setting up the test equipmentThis section provides an outline

of detailed adjustments for single -tube color cameras. Also includedis a description of the function ofeach of the major circuits andsome service hints.

The outline is not meant toreplace the manufacturer's servicemanual, but to serve as a generalguide. Specific circuit descriptions

and alignment procedures for yourindividual camera can be found inthe manufacturer's manual

General setupCamera testing begins with the

setup of your measuring equip-ment. Your adjustments can be on-ly as accurate as your test equip-ment. As previously discussed, allalignment procedures should beperformed under 3200°K lights,set to a level as indicated by thecamera's sensitivity specification.The video output of the camerashould be routed to the waveformmonitor, vectorscope, and, finally,to the color output monitor. Ifyour camera has test -monitorcapability, connect this output to aB&W monitor for registration ad-justments.

Remember that the last piece oftest equipment in the video chainmust be terminated in 7551. Alltest equipment that the video

PRE -AMP

LOW-PASSFILTER

TP 1

BAND-PASSALTER

Key adjustment check points

TP1 Adjust frequency response to match that of stripe filter.TP2 Adjust deflection for minimum carrier frequency leakage.TP3 Adjust for maximum carrier frequency.TP4 Adjust for 0.7 volts at manufacturer's specified lens opening.

TP5,6,7 Adjust for same level of B&W signal for best color balance.

TP7 Confirm best deflector levels by checking for maximum color.

TP 2

TP 3

LO W PASSFILTER

REDPROCESS

BLUEPROCESS

TP 4

TP 5

TP 6

TP 7

Figure 1. Block diagram of color camera shows key adjustment check points.

B-YLMATRIX


signal loops through must be unter-minated. Failure to terminatevideo lines properly will result inthe camera's output appearinggreatly distorted. Unterminatedlines expand the video and synclevels, causing the picture to ap-pear excessively bright. Doubleterminated lines suppress thevideo and sync levels and cause thepicture to appear excessively dark.After confirming that the videoline is properly terminated, youcan proceed to calibrate the testequipment.

Calibrating test equipmentWaveform monitor setup:

1. Allow the waveform monitorto warm up for at least 15 minutesbefore beginning setup.

2. Rotate the intensity controlclockwise until the trace is at thedesired brightness. Be careful notto turn the intensity control up tofull brightness, because operatingthe CRT in this manner for longperiods of time can greatly reduceits life.

3. Use the vertical position con-trol on the trace to place the beamon the 0 IRE graticule line. Usethe horizontal position to start thebeam trace at the first major divi-sion mark on the 0 IRE graticuleline. This is located on the left sideof the waveform.

4. Now set the VOLTS FULLSCALE switch on the 1V CALposition. Use the vertical positioncontrol to center the display ver-tically in the - 40 to 100 IRE unitarea of the graticule. Thiscalibrator waveform sets the lower(sync tip) and upper (white peak)limits on the video signal.

5. If the calibrator signal ap-pears to lack definition, adjust theastigmatism and focus controls toobtain a well defined waveform.Vectorscope setup:

1. With no signal input, adjustthe intensity until the beam can beseen. As with the waveformmonitor, be careful not to set theintensity level of the CRT too high,as damage can result. Allow thevectorscope at least 15 minutes towarm up.

2. Use the focus control to ob-tain the best -defined beam.

3. Use the horizontal and ver-tical position controls to move thebeam to the crosspoint of thehorizontal and vertical graticules.

4. Depress the mode select but-ton (gain control) twice. The testcircle will appear. Confirm that thecircles are all concentric and theoutermost circle is equal to thegraticule circle.

5. Set the camera's outputsignal to color bars. This is wherethe camera acts as a test

generator. Use the signal to con-firm that the individual colors fallwithin their appropriate 2.5° and2.5 IRE graticule boxes. The burstsignal should be found directly onthe 0, 180° line. If the total color -bar signal appears to be shifted inposition, use the vectorscope'sphase control. Make sure you usethe burst signal as a reference.

Prior to setting up the last pieceof test equipment, the color videomonitor, recheck the signal on thewaveform monitor and vec-torscope to confirm that the signallevels are properly set. If anydeviation is found in the sync levelof the waveform monitor and/orburst level of the vectorscope,recheck your cable terminationbefore proceeding.

Monitor set upPreviously, we covered most of

the common operational monitorchecks. Many types of monitorsare used, not just for viewing, butalso as test fixtures. When relyingon the monitor to judge thecamera's color reproduction, it isextremely important that the colorbalance of the monitor be correct.This adjustment can be performedonly if your monitor has ad-justments for the three individualguns: red, blue and green.

Begin this procedure by ad -

WAVEFORM

MONITOR

VECTORSCOPE

VIDEOMONITOR

Figure 2. Color camera test setup. The last point in the video chain must be terminated in 750.


Continued from Page 19hours, chasing potential problemsthat ultimately never existed in thefirst place. We now manufacturesuch a device. It's called our MarkVI Diagnostic Computer.

If you work on a lot of equipmentthat employs any type of atransformer, (i.e. the horiz sweeptransformer in a TV set), you will nodoubt want to consider one of ourslightly more sophisticatedcomputers. Take TV service as anexample, our Mark VII Computerprovides you with two separatetwelve unit bar graphs. The first bargraph gives you a read out onresistive load power consumption.The second bar graph gives you aread out on inductive load powerconsumption. Both graphs provideyou with an open and a normal readout, both employ current limitingcontrol.

WHAT DO THESEBAR GRAPHS TELL YOU

ABOUT TV SERVICE?First off, just a few examples:If the red "nine" or "ten" light is litin the resistive bar graph, it's time tostart changing the LV rectifiers.With these lights lit, the short ispositively located on the B + side ofthe primary winding of the (horizsweep) transformer. It cannot beanywhere else. If the red "six" or"seven" lights are lit, either thehoriz output transistor is shorted, orsomething on its collector line isshorted, (i.e. damper diode, safetycapacitor, pin cushion transformer,discharge capacitor for the horizyoke circuit, etc.). A short thatproduces a red light in the resistivebar graph will not be, and cannotpossibly be located on the secondaryside of the sweep transformer, it hasto be on the collector line of thehoriz output.A red "nine" light in the inductivebar graph and the TV set either has ashorted CRT, or a shorted HVtripler. A red "eight" light means ashorted scan derived B+ rectifier,or its associated filter capacitor, andso on. Each light, in each of the bargraphs has a very specific meaning.The best part is, thus far, youhaven't so much as taken the backoff the TV set so long as the horizosc / driver, and the LV regulator isfunctional. If one or the other is notfunctional, you will naturally haveto substitute it with horiz driveinjection to the base of the set'shoriz output transistor, or in the

ADVERTISEMENTcase of an in -op LV regulator,restore primary low voltages.

Aside from looking at the powerconsumption label on the equipmentunder test, then, setting thecomputer's range control to thatsetting, absolutely no programmingis ever required to operate either ofthe above computers. Just turn theequipment on, turn the computeron, plug the repair job into thecomputer, push one single buttonand look at the bar graph(s).If you do not do TV work, the MarkVI will do everything you will everwant done. If you work primarilyon TV sets, plus any otherequipment that comes in, you willmost definitely want the Mark VIIunit. (You will not need both).

You might say that the Mark VI issomewhat like a variac that permitsyou select the amount of wattage(instead of voltage) that you wish toapply to a circuit, with a built-incomputer that tells you if a resistiveshort exists in the equipment undertest, and if so, what type of a shortexists, and just how severe it is.

The Mark VII does all of the above,except that it has an additionalcomputer that tells you whether theshort is resistive or inductive (on thesecondary side of a transformer),and again, just how severe the shortis.

The watts output range of bothunits is 25, 50, 75, 100, 125, 150 thru250 watts in 25 watt increments. Thegreatest part is, if a short exists, youcan't tear anything else up (such asadditional components). In theevent of a short, the computersimply lights one of the "short"lights in it's bar graph. Based onwhich light is lit, you now knowessentially where the short is.

Once a short light comes on, thecomputer immediately reduces it'soutput to whatever level is"comfortable".

As you are about to see, the MarkVII unit is expandable (the Mark VIis not expandable).

IF YOU PREFER NOT TOWORK AT ALL:

Then you will want to purchase aMark VII computer, and considerthe following self contained "addon" computer which we haveappropriately named the"Eliminator" (for obvious reasons).Since it is a plug in expansion system

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for the Mark VII, you can add an"Eliminator" package to yourMark VII at a later date.The "Eliminator" expands thefeatures that are found in the MarkVII units. It's main frame is builtaround an eighty square inchgaseous display panel whichprovides you with a generic blockdiagram of the entire lv, lvregulator, horiz output, horiz sweepcircuits, scan derived B+ sources,horiz oscillator and driver circuits,horiz yoke & P.C. circuits, vertical,color output, start up, shut downand B + run circuits (to name just afew).

With the "Eliminator", all you dois set the same power consumptionswitch, plug the TV set into thecomputer, turn it on, then, pressjust one single button. The gaseousdisplay will now light up the stage,circuit, or in many instances, theactual component that has failed. Ininstances where the TV set's horizoscillator, driver or output is notoperational, the "Eliminator" willlight an instruction telling you tointerface to the set's horiz outputdevice. When this happens, removethe TV set's horiz output device(transistor or SCR), and plug in thecomputer's interface plug (whichlooks like a horiz output transistor).Then, press the test button again. Asimilar instruction is given forinstances where the TV set's LVregulator must be analyzed. In someeighty percent of all cases, neitherinstructions will be given becauseneither will be required for the"Eliminator" to analyze the entireoverall circuit.Yes, this means that you canvirtually analyze most TV sets rightdown to circuit level in everyinstance. And, right down to veryspecific component level in mostcases without ever taking the backoff!

In fact, the only instances that willrequire you to remove the back inorder to do so with virtually 100%accuracy, are cases where the TVset's horiz osc / driver, or outputstages are in -op. Or, in cases wherethe LV regulator circuit is notcooperative. Virtually no other typesof circuit failures will require theremoval of the TV set's back for anaccurate diagnosis to circuit level!

In fact, the "Eliminator" will spotany type of a shorted condition andmany types of open conditionswithout removing the back, andwithout you're even so much aslooking at the set's CRT.

Under the above conditions, theContinued on Page 59

justing the monitor's brightness,chroma and phase controls, but,first, review the setup of thesecontrols that begins by inputtingthe camera's color -bar signal.

1. Turn off all monitor presetsand turn down the chroma controlto its lowest position.

2. Adjust the brightness controluntil all levels of the individual col-or bars can be seen clearly.

3. Adjust the chroma level untilcolor can be seen.

4. Adjust the phase control untilthe yellow bar appears to have thepurest hue, or most yellow ap-pearance.

Now you can take advantage ofthe setup control found in themore sophisticated types ofmonitors.

White balance adjustment1. Set the color monitor to the

monochrome mode.2. Place the monitor in the SET-

UP or TEST mode. This switchsuppresses the horizontal scan to asingle line.

3. Turn off the red and bluechannel guns. Next, adjust thegain of the green channel until you

can see a complete line. Turn offthe green gun and repeat this ad-justment, using the blue and redchannel gains. If all gains are setto be uniform, the combination ofthe red, blue and green guns willproduce a white line. If the line ap-pears to have a tint of a particularcolor, lower its gain. If colorbalance is not achieved, it will benecessary to repeat this pro-cedure.

Remember that the perceptionof white will differ with each in-dividual and the conditions ofviewing. Depending upon theseconditions, white can appear to begreenish, reddish, yellowish orsome other slight tint. For thisreason, there has to be an agreed -upon value for absolute white. Aswith color cameras, we can use col-or temperatures and measurewhite in terms of the Kelvindegrees. The standard for NTSCmonitors is approximately9300°K.

In addition to color balance ad-justments, high grade monitorsalso have provisions for aligningthe scan of the individual guns.This type of adjustment is similar

to registration of a camera. Whileviewing the color -bar signals withthe monitor set to the mono mode,check to see that the transitionpoints between the bars are clearlydefined by a single line. This checkis limited to horizontal resolutionerrors only. Some monitors con-tain an internal test signalgenerator for adjusting con-vergence. Ordinarily, these ad-justments are unnecessary.However, it is a good idea to checkthe monitor's convergence so thatmonitor scanning errors will notfrustrate you during camera setupand registration.

When monitor setup is complete,check to see that the monitor is setto the color mode, and switch yourcamera from the color bar to theoperation mode.

The single -tube color cameraThe single -tube color camera

combines the separate red, greenand blue tubes found in a 3 -tubecamera on a color stripe filtersystem so that the three individualcolors can be reproduced by asingle tube. Refer to article one ofthis series (ES&T, December1985) for a review of how thesefilters create color. Because thiscamera processes signals from on-ly a single tube, the electronicsthat would have been associatedwith the two additional tubes aredispensed with. All the major func-tions of signal processing can beconfined to two printed circuitboards. One handles video process-ing, and the other, sync genera-ting and deflection processing.

As with any type of colorcamera, the quality of picturereproduction depends on theoperation of the type of tube, andoperation of the sync and deflec-tion circuits. The single -chip syncgenerator creates all the majorpulses needed to produce the com-posite signal. The horizontal and

Pickup tube positioned in yoke assem-bly. If front of tube loses contact withtarget, picture output will be zero.


Vectorscope trace shows misadjustedstripe filter.

vertical deflection pulses are in-tegrated into sawtooth wave-forms and applied to the deflectionyokes. The horizontal drive iscoupled to the high voltage circuitand is used by the dc -to -dc con-verter to create the high voltagesupply for the pickup tube. In addi-tion, the high voltage supply alsopowers the beam and target. Ver-tical and horizontal deflectionpulses are changed into parabolicand sawtooth waveforms by aseries of integrators for use in thecamera's shading circuits.

The sync and deflection boardalso contains the encoder circuits,which use the subcarrier from thesync generator for R -Y, B -Ymodulation.

Video processingThe signal from the target out-

put enters the pre -amplifier and isamplified by a series of transistorsstarting with an FET amplifier.The weak signal from the pickuptube must be amplified with a con-sideration to maintaining a highsignal-to-noise ratio. From thepre -amplifier, additional signalprocessing will result in loweringthe overall S/N, because of noiseadded by the video processing cir-cuits. Usually, in order to maintaingood S/N, a portion of the signalfrom the last transistor amplifieris fed back to the first -stage FET.This results in a better conditionfor signal transfer and improvedfrequency response.

For the 3 -tube color camera, theprimary consideration for frequen-cy response centers on depth ofmodulation. In the single -tubecamera, the frequency response ofthe pre -amplifier directly affectscolor reproduction. Rememberthat the beam scanning across thestripe filter will produce a carrierfrequency. This frequency thenwill be used to create red, green,and blue. The frequency response

of the pre -amp must remain flatsafely past the point of the carrierfrequency.

After the signal enters the videoprocessing board from thepre -amp, the signal is do clampedand amplified. The signal then isdivided by means of low-pass andbandpass filter systems. The low-pass filter blocks the color carrierand allows the luminance signal topass. This signal, known as YH,contains all the picture details, andafter passing through an addition-al low-pass filter, a cut-off point of0.5MHz will be used to create theYL or green component.

The red and blue componentsbegin by being separated from theluminance carrier by means of abandpass filter, whose center fre-quency is equal to the carriercreated by the horizontal scan andcolor stripe. Like the luminancesignal, the color carrier is furtherseparated into its red and bluecomponents. This is accomplishedby taking advantage of the90° -phase difference between thetwo colors created by the differentangles of the cyan and yellowfilters. Finally, the red and bluecarriers are added to the green

(YL) signal, to form the R-YL,B-YL signal input for the NTSCencoder.

Camera adjustmentsStart by reviewing some of the

concepts covered in article two(ES&T, January 1986): Pro-cedures begin by creating the rightconditions. Allow the camera towarm up for at least 20 minutes.

Adjust the 3200°K lights to thelux or footcandle level indicated bythe sensitivity specification, or asotherwise indicated by themanufacturer's service manual.Remember to set the camera'sfilter or color -control switch to3200°K light. Open the camera'slens to the setting indicated by thecamera's sensitivity specification(usually f4 or, f5.6) or as otherwiseindicated by the manufacturer'sservice manual.

Finally, make sure you have theproper test charts available. Forthe single -tube camera, ad-justments will use the logarithmicgray scale, a white card and achart to check color reproduction.Most manufacturers provide a testchart with the camera to test colorreproduction.


You might have noticed that wehaven't included a registrationchart. The single -tube camera willnot require any registration. In ad-dition, geometric distortion will bedetermined by the setting of thebeam deflection to obtain the bestpossible stripe filter output. Youwill have to live with anygeometric distortion after the scanis set up. Many technicians haveattempted to use the registrationchart to set geometry and havebeen left frustrated, wonderingwhy color reproduction is poor.

Adjustments1. Power Supply: Always begin

any camera adjustments by check-ing the power supply. Becausesingle -tube cameras are so depen-dent on proper stripe recovery forgood color reproduction, powersupply problems can make thisrecovery impossible.

You will notice that the averagesingle -tube camera will not havethe variety of adjustments offeredby the 3 -tube camera. Industrialsingle -tube cameras will distin-guish themselves from consumerversions by having adjustableblanking. Most consumer -modelcameras have fixed output syncgenerators with no adjustments.

When the camera does not have

an internal color -bar generator,perform the burst phase andchroma gain adjustments in thefollowing way:

Focus the camera on a skin tonepattern. For adjusting the camerain this way, you will be dependenton the color monitor for judgingthese settings. In order to use thecolor monitor most effectively as atest fixture, it must be preset witha color -bar generator. Remembernot to leave the monitor in thepreset condition. Adjust for bestreproduction of skin tone oryellow.

Note: Prior to making any elec-tronic adjustments, preset alloperator controls to their centerpositions and recheck the elec-tronic color balance setting for3200°K. Preset all static shading(dark shading) and all dynamicshading (target shading) adjust-ment controls to their mechanicalcenters. This will give you a max-imum range after the adjustmentprocedure has been completed.

2. Electronic Focus: Looking atthe output of the bandpass filter(red and blue) adjust the electronicfocus to obtain the maximumsignal. Because blue is the hardestsignal for the stripe -filter systemto reproduce, also check for max-imum blue signal output.

Next set the physical position ofthe tube for best back focus anddeflection. Loosen the tube -holding screw located on the yokeassembly. Hold the tube socketwith your fingers. Exercise cau-tion as the socket can containvoltages as high as 1,000 or moredc. Although the amperage is low,the shock will be enough to wakeyou up.

3. Tube back focus: Zoom thelens in and rotate the lens focusring to achieve the best picture.(Remember not to touch the elec-tronic focus, as it was previouslyset for best stripe filter output).Zoom the lens out to its farthestposition. If the picture looks out offocus, pull the tube backwards inthe yoke for the best focus posi-tion. Be careful not to pull the tubetoo far back as it can lose contactwith the target, causing thecamera to have no signal output.

4. Beam deflection: Observe thesignal output at the bandpassfilter. Rotate the tube until thesignal is as flat as possible. Thereason for this is that the beammust cross the stripes to defineeach one clearly: yellow, clear andcyan. This means that the angle ofintersection must yield maximumfilter resolution. Due to the dif-ference in each of the stripes, theresponse will not be completelyflat, causing the output of eachstripe to vary.

This is a critical adjustment forcolor reproduction. The beam scanacross the color stripe must pro-duce the exact carrier color fre-quency throughout the entirehorizontal scan. Distortion at anypoint in the scan will cause the car-rier to leak into the YH (luminancesignal) and reduce the amplitude ofthe red and blue signals. As aresult of this, it will not be possibleto achieve unity of the threeprimaries in that part of the pic-ture. In most cases, the base colorof green will prevail, and the pie -

Waveform monitor display showspresence of chroma in B&W areas.


ture will take on a green orgreenish -yellow hue.

To make this adjustment, youmust first calculate the duration ofthe carrier sine wave. Do this bydividing the stripe filter into 1 asspecified by the manufacturer.This results in the time period ofcarrier frequency.

For example, assume that thecamera in question has a 3.8MHzcarrier.

The period would be:

1

3.8MHz = 0.25µs.

You can use the delay mode ofthe scope to view this signal.

5. Horizontal size: Locate thecenter of the horizontal line andadjust the sine wave for a 0.25µsduration. When viewing the out-put of the PBF, adjust for max-imum amplitude at the center ofthe waveform. When viewing theoutput of the LPF, adjust for

011%

ONla

This waveform monitor display, with the camera focused on a gray scale subject,shows properly adjusted color balance.

Symcures WantedElectronic Servicing and Technologyneeds a broader variety of television Symcures.Especially needed are reports of Quasar,General Electric, Sylvania (or Philco), Sony Searsand Magnavox.

Symcures are, by definition, solutions toproblems that have been encountered during therepair of more than one television set of thesame make and model, and that may reasonably beexpected to be a source of recurrent failure.

Please give the brand, model number,Photof act number, a brief description of thesymptoms, a rough hand -drawn schematic of thearea containing the defect, and a shortdescription of the cure (including whether thedefective component was open, leaky, shorted orintermittent).

ES&T editors will adapt the material to theSymcure format and have Photofact-styleschematics prepared.

Send seven Symcures each time. Only six willbe published, but the extra gives the editor aspare for one already printed in the past (orotherwise not suitable to the format). $30 will bepaid for each page of six actually published(remember to include full name and address).

Send to: Symcure DepartmentElectronic Servicing and TechnologyP.O. Box 12901Overland Park, Kansas 66212

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minimum amplitude at the centerof the waveform.

6. Horizontal linearity, Lin -1,Lin -2: Locate the start of thehorizontal line and use the delaymode to observe the individual sinewave. Adjust the correspondinglinearity control for a 0.250 dura-tion. When viewing the output ofthe BPF, adjust for maximumamplitude at the beginning of thehorizontal line. When viewing theoutput of the LPF, adjust forminimum amplitude at the end ofthe waveform.

When doing the linearity adjust-ment, one control will affect thebeginning of the waveform and theother control will affect the end ofthe active video horizontal line.

Note: In setting the horizontalscan, you established a consistentcarrier frequency for each horizon-tal line. Even though the verticalscan is made up of horizontal lines,you still must adjust the verticalscanning so that the frequency ismaintained for each field. Whenthe horizontal and vertical scansare properly adjusted, theresulting frequency will be that ofthe carrier. This is the zero fre-quency. When the rate of vertical

scan is offset, the rate of the car-rier is changed at the particularpoint, top, middle, or bottom of thepicture. In electronics, when twoidentical frequencies are slightlyoffset, they beat. The furtherapart they are from each other, themore they beat. The closer theyare, the less they beat. And whenthey are the same, no beating, orzero beating occurs.

Red -blue separation adjustmentAfter the signal from the pre -

amp passes through the BPF, thered and blue color signals stillmust be separated. The total colorsignal is a combination of twohorizontal lines. To separate thecolors, the camera electronicsmust shift the signal 90° in orderto match the phase shift created bythe physical layout of the colorstripes. Adjusting the R/B separa-tion electronically adjusts the90° -phase shift, therebyregulating the amount of red/blueseparation.

Vectorscope display shows good blackcolor balance and proper reproductionof yellow/fleshtone.

At this point, you have createdseparate red, green and bluesignals, as well as a luminancecomponent that contains the pic-ture details. The adjustments fromthis point will depend on matchingthe pedestals and gains of the red,green and blue signals to achieve aunity of gain for proper whitebalance.

This adjustment is accomplishedby focusing the camera on the grayscale and using the oscilloscope tomatch each of the primary channeloutputs. If you have a vectorscopeor waveform monitor, you can per-form this adjustment by looking atthe composite output. In the caseof the waveform monitor, look forminimum subcarrier leakage. Inthe case of the vectorscope, com-press the signal into the center,which represents an absence ofcolor or black.

Confirm tacking adjustments byirising the lens down and lookingfor chroma in the waveform.White balance must be maintainedwith changes in incoming light.

Finishing the adjustments:your personal opinion.

As previously noted in thisseries, color cameras are unlikeother types of video equipment inthat performing adjustments bythe book does not alwaysguarantee the best results. Beautyis in the eye of the owner. Oftenyour perception of blue, green andred can be different from that ofthe user. Because of this, part ofthe adjustment process requiresthat the end result please the con-sumer. With color cameras therecan be many variables to that finalgoal. As a personal suggestion,and not one found in the servicemanual, attempt to show the userthe camera picture. The little extratime it takes to answer questions,clear up misconceptions and do alittle bit of final color adjustmentcan go a long way toward ensuringuser satisfaction. Always keep inmind that the repair of a colorcamera is a balance between thefacts of electronics and the opinionof the user. (Env,


SPLISHSPLASH

RepairingFlood Damaged

Electronic EquipmentLast fall, five days of heavy rains

pelted the East Coast. In the FallsChurch, VA, area, the rivercrested 11 feet above flood stage,but 80 miles upstream in themountains it became a 54 -foot highwall of water that overwhelmedthe best efforts of hundreds ofbone -tired volunteers. Despitebackbreaking heroic efforts, thesandbag wall at the edge of onetown gave way. Over the next24 -hours, the water rose, floodingbasements and gushing into thefirst floor of most homes andbusinesses to a height of six feet.As the waters receded, the gover-nor called out the National Guardto prevent looters, and peoplereturned home to recover whatthey could. After cleaning out thewater moccasins that inevitablycome along with the flood waters,they found their possessionssoaked and mudcaked. Among thedamaged goods were electronicproducts, which they hoped couldbe salvaged. Would you know whatto do?

Although most flood damage

scenarios are not as dramatic asdescribed, it does happen. Andfrom time to time you hear of elec-tronic equipment that has taken abath: boating accidents, plumbingfailures ("Gee! was that plasticpipe running just above my stereoset?") and a variety of other prob-lems can splash equipment out ofservice. Fortunately, there arecertain things that a skilled techni-cian can do to restore operation.

If the insurance company paysoff well enough, then the flood vic-tim could buy a new product. But ifthe insurance company refuses topay ("Sorry...wind driven waterdamage excluded..."), or if there isno insurance, then restorative ac-tion might be indicated. Even ifthe insurance company does payoff, the owner often can buy theequipment back for salvage value.Someone I know received $325 fora 2 -year old 2 -way radio andbought it back from the insurancecompany for $20. The companysent him a check for $305, and hekept the carcass.

Some of the steps that I recom-

mend may sound a little bizarre toyou from a normal perspective.They make it possible to restore anexpensive piece of equipment,however. Some of the steps mightcause a little damage that also willhave to be repaired (especiallythose involving baking themoisture out or using chemicals toclean the rig). If that makes younervous, then please rememberthat in the case described you can-not harm the equipment anymore:IT IS ALREADY A TOTALLOSS! Any restoration is puregravy.

It should be understood that youare undertaking heroic measuresthat may not be successful.

The first thing to do is refrainfrom turning the set on, even for abrief test to see if it is broken.Satisfy yourself right now thateven a short dunk will cause fataldamage. Still, the all -too -naturalurge is to see if the equipment sur-vived the flood: If it was im-mersed, then it didn't survive.

The first job is to remove thecovers and give the rig a bath.


When I first started writing forES&T, I lived in an easternseaport town where saltwaterdamage to electronic equipmentwas common. The shop where Iworked part-time (while attendingengineering school) received a$1,800 UHF -FM taxicab radiotele-phone set that had been immersedthe night before during a storm (itseems that the saltwater rivertributary overflowed its banks justhigh enough to cover the radiomounted in the trunk well). Thefirst thing the shop owner did wastake the transceiver out on theback parking lot and give it a10 -minute shower with a gardenhose. He had lived in that town allhis life, and therefore had muchexperience with water damagedradio gear.

Incidentally, if the damage iscaused by saltwater, then do thecleaning job immediately, if notsooner. The longer salt residue re-mains in the equipment, thegreater will be the corrosiondamage, and the lower the chanceof successful restoration.

In some cases, it will benecessary to follow the showerwith an immersion bath. A techni-cian I know uses a 25 -gallon tub,the kind you might use to give alarge dog a bath. He mixestogether in the tub two to fourquarts of liquid grease -cuttingdetergent, a small bottle (2 to 4 fl.oz.) of fingernail polish remover(acetone) and enough tap water tofill the tub all the way to the rim.Leave the set in the bath for anhour, and then pour out the solu-tion; rinse the tub out thoroughlyand refill with plain tap water(some people prefer distilledwater, which is available in bottlesin most areas). This second bathremoves the residue left by thechemicals in the first bath.

Note: This bath may damagesome plastics. If this worries you,then use plain soapy water. It isn'tquite as effective as a solvent, butit works to a degree. Keep in mindthat most plastic pieces can bereplaced, and the damage usuallywill not prevent the set fromoperating: It is already a total loss,so don't worry about trivial secon-dary damage.

The next step is drying the unitout thoroughly. If you live inArizona (yes, they have floods inthe desert), then simply leave the

rig out in the sun for about a week;everyone else will have to usesome other method. The kitchenoven is a good bet, provided that itcan be regulated to maintain atemperature of 125°F to 130°F.That range is low for a kitchenoven, and some might not bedesigned to remain that cool. Butbeware - higher temperatures willdry the set out faster, but they alsowill melt some of the plastics usedin it. The drying process takesseveral days, perhaps as long as aweek.

Another alternative is to build acardboard (or other material) boxand use several hundred watts ofincandescent lamps to provideheat. Use a thermometer insidethe enclosure to ensure that A.)the 130°F melt limit is not exceed-ed, and B.) the box doesn't catchfire from neglect (cardboardburns). Again, up to about a weekis needed, although I have driedout a car radio that was dropped infresh water (for a few minutes) inonly one day.

Now comes the Big test. In somecases, the only way to test theequipment is to turn it on and lookfor smoke. I prefer a more conser-vative approach that sneaks up onit one step at a time. My first stepin the test is to disconnect the dcpower supply; this step can be ab-solutely essential to the futurehealth of the set being re-paired - especially those with highvoltage (HV) power supplies.

Without connecting the set to acpower, connect a bench power sup-ply to the circuitry that waspreviously connected to the rig'sinternal power supply. It is essen-tial that you use a do power supplythat will provide the samevoltage(s) as the original internalsupply, and in addition (this is im-

portant) has a current limiter con-trol (Figure 1). The output voltageis set to the do voltage normallysupplied by the rig power supply,and the current limiter control isset for a short-circuit current onlya little above the normal operatingcurrent of the circuit under test.

Why go to such trouble? Thereason is prevention of majorsecondary damage. There isalmost inevitably a short circuit orother condition that draws loads ofcurrent. If such a condition existsin the equipment, then the internalpower supply in normal use proba-bly produces enough current toburn up components, printed wir-ing board tracks and other ad-juncts. After the circuit is checkedout, then you can check out thepower supply and, if working,reconnect it.

The low -voltage do power supplyshould be checked out separately,especially if it uses a series -passregulator as many sets do. If theregulator circuit is not working,then several possible faults allowthe rectifier output to be con-nected to the regulator output;this occurs when the series -passtransistor is either shorted or hardbiased to full turn -on. Since therectifier voltage always is higherthan the regulator output voltage,it can damage circuits that werejust pronounced healthy.

High -voltage power supplieshave special problems. Smallamounts of moisture that are noproblem in low -voltage supplieswill zap a HV supply into never-never land. The special problem isthe HV transformer. If moisturehas penetrated the transformer,then it may have to be replaced. Itmay help to provide some extradrying for the transformer, but beprepared to replace it. Figure 2


110

nINCANDESCENT

LAMP

VAC

o

Figure 2.

shows a method for drying a powertransformer. A 115Vac lamp inseries with the primary of the HVtransformer allows enough cur-rent to flow to cause internal heatbuild-up to accelerate drying, butnot enough to zap the tranformerif it is shorted. If the HV powersupply uses a 220Vac primary cir-cuit, then place one lamp in serieswith each ac hot line. (See Figure2, above.)

Some remaining areas of con-cern and probable damage are

those components where moisturecan get in and remain hidden.These include: trimmer capacitors,air variable capacitors, IF and RFtransformers, switches and poten-tiometers, paper capacitors andelectrolytic capacitors.

You can open trimmer capa-citors up to the minimum capacityposition (screw all the way out)and apply a hair dryer or incandes-cent lamp for 10 to 15 minutes.Whether this step is needed can bedetermined after the initial power -

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on test shows a specific problem.Otherwise, you will mess up thealignment of the set for nothing.This step should not, therefore, beused merely as a matter of course,only in response to a specific symp-tom. Now you know what to do.

Similarly, air variable capacitorsmay have corroded contact wipersbetween the rotor and stator, andthis will be apparent when the rigis turned on.

Paper and electrolytic capacitorscan absorb water, especially if theyhave a fiber or cardboard end cap.If the capacitor shows signs of be-ing soggy, then replace it;capacitors are, after all, relativelylow-cost items.

If there remains a lot of scum onthe printed wiring board, thenspray -clean it with Freon TF orsome similar material. I prefer touse a small paint brush or cheesecloth to help remove the residue.

You will find that flood -damagedsets often are salvageable. Themethods described have been usedby professional service techniciansfor a lot of years, and are provensuccessful. nu

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What do you knowabout electronics?

The padderSome time ago, I wrote an arti-

cle about the use of paddercapacitors. What followed was acontroversy about whether pad-ders should be adjusted at the highend or low end of the band.

Both sides of the argument werepresented, and it looked as thoughthat would be the end of it.However, Antonio Moreno, CET,has sent an interesting write-up onthe padder. His background is withthe military, which is a viewpointthat has not been considered here.The material he sent follows.

In some early superhets, gangedcapacitors were made with iden-tical ganged sections. When bothsections of the capacitor wereidentical, the total capacity of theoscillator tank circuit was reducedby placing an adjustable micacapacitor, called a padder

By Sam Wilson

capacitor, in series with theoscillator tuning capacitor. In theprocess of alignment, the paddercapacitor was adjusted for perfecttracking at the low end of theband. The process of adjusting thetuned circuits, to maintain thisconstant difference at both thehigh and low ends of the tuningbands, is known as aligning.

In order to align the superhet atthe high -frequency end of theband, trimmers are placed inparallel with each section of thetuning capacitor.

What is perfect tracking?Perfect tracking is the condition

when the oscillator tuned circuit isresonant exactly 456kHz higherthan the RF-tuned circuits for allsettings of the tuning dial. Themixer and oscillator circuits of a

GANGED TUNING CAPACITORS

RF TANKCIRCUIT

PADDER

OSCILLATORTANK CIRCUIT

Figure 1.

againsuperheterodyne are said to trackwhen these circuits maintain aconstant frequency difference be-tween them throughout the tuningrange. The frequency difference isthe intermediate frequency (IF).

Because the oscillator circuitgenerally is set to a frequencyhigher than that of the mixer andRF circuits, the capacitance andinductance of its tuned circuit isusually smaller. Also, for thehigher oscillator frequency, thepercentage of frequency shift forthe oscillator tuning capacitormust be smaller for the same tun-ing range than that of the mixerand RF capacitors.

The lower capacitor shift isachieved in some receivers by us-ing a smaller coil and a smallertuning capacitor with speciallyshaped plates in the oscillator cir-cuit. (The special shape of theplates ensures tracking through-out one frequency band.) Thismethod cannot be used, however,in multiband receivers, becauseeach band requires a differentlyshaped oscillator tuning capacitor.

In some designs, the tuningcapacitors for the RF andoscillator circuits are the samesize. The required frequency dif-ference then is made up with asmaller oscillator coil. Tracking isattained with trimmer and paddercapacitors. The trimmer is con-nected in parallel with theoscillator tuning capacitor, and thepadder is connected in series withit as shown in Figure 1.

At the high frequency end of thetuning range, the oscillator -tuningcapacitor is set for minimumcapacitance. The parallel trimmer


has about the same order ofmagnitude as this minimum valueand its adjustment determines theproper resonant frequency at thisend of the frequency range.

At the low frequency end of thetuning range, the capacitance ofthe oscillator -tuning capacitor isnear maximum, and, therefore,the small parallel trimmer isnegligible in comparison with it.Now, however, the series padder iscomparable in magnitude to themain tuning capacitor and affectsthe resonant frequency.

The value of the padder is usual-ly about two to four times themagnitude of the maximumoscillator -tuning capacitance.

Because the total capacitance oftwo series capacitors is influencedchiefly by the smaller of the twocapacitors, the effect of the seriespadder on the total tuning capaci-tance at the low -frequency end issmall, but suffices to set the reso-nant frequency within the limitsrequired for proper tracking.

By proper adjustment of thepadder and trimmer capacitors,reasonable tracking accuracy can

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33k //

//

/

y/ \/ \`

/ N20k \

\

50k

Figure 3.

be attained throughout the fre-quency range. If several bands areused, separate trimmer and pad -

der capacitors are usually providedfor each band.

Graphing the junk box partsI'm convinced that some of the

construction projects I've readabout have only been built in theauthor's mind. Successful comple-tion requires a mythical "JunkBox" that is stocked like a partssupply warehouse.

The articles usually have a keysentence that goes like this: "Thisproject can be constructed in oneevening using parts from yourjunk box. You will need agoniometer, a cosine resolver, a10 -turn logarithmic pot, a workinghead from an old magnetometer,and a magnesium bar with dimen-

sions of 5"x3"x17". Get the rest ofthe parts (resistors and capacitors)from your local supply.

Some day I want to see one ofthose junk boxes.

What I have seen are boxes ofresistors and capacitors that havebeen saved for future use. Thevalue you need is seldom there, soyou end up putting two or threeresistors in series so you can getyour project into operation.

Parallel combinations are goodbecause they can handle highercurrents and run cooler. Agraphical solution makes it veryeasy to select the required parallelvalue. The following exampleshows how easy it is.

You need 20k. You have a 33kresistor and a box of unlikelychoices. Start by drawing a baseline on the graph paper.

Make a vertical line that is pro-portional to the value you want(20k), and another line propor-tional to what you have. Figure 2shows what you now have. Youcan draw the lines any convenientdistance apart.

Connect and extend the ends ofthe lines as shown in Figure 3.Observe the point where the linewith a negative slope crosses the Xaxis. Figure 3 shows how yourdrawing should look.

Draw a vertical line from thepoint marked on the X axis. Ex-tend that line until it crosses theline with the positive slope. Thelength of your vertical line will beproportional to the value you need.The graphical solution shows thatyou need about 50k.

I don't know where you will finda goniometer. Welt,


Literature

An 18 -page supplement to thecurrent ECG semiconductorsmaster replacement guide, thethirteenth edition, has been madeavailable by the Distributor andSpecial Markets Division ofPhilips ECG, a North AmericanPhilips company. The new supple-ment contains information up-dating coverage of the masterguide that lists more than 3,500ECG solid-state replacements forforeign and domestic types used inentertainment, commercial and in-dustrial equipment includingmaintenance, repair and opera-tions (MRO).

Technical information is given inthe supplement for 41 new ECGsemiconductor additions that ex-pand the ECG line to almost 3,600types. The supplement's cross-reference section lists some 4,500entries including new replacementinformation and some cross-reference changes to the masterguide.


VIZ Test Equipment, a divisionof VIZ Manufacturing Company,has announced its 19 -page, powersupply and test equipment catalog.A guide to the manufacturer's fullline of test equipment includeslaboratory and industrial do powersupplies, isolated ac powersources, frequency counters,analog meters, signal generators,testers, digital meters and watt-meters.

Each product section presentsphotographs, descriptions andspecifications, VIZ's latestliterature, the VIZ warranty state-ment, and a list of warranty serv-ice centers and sales officesthroughout the country.


"Everything You Need To KnowAbout Home Satellite TV" is the ti-tle of a new 16 -page bookletavailable free to consumers fromLuxor North America. It answers78 of the questions most frequent-ly asked about satellite television.

The question and answer booklet

is organized into seven sectionsunder the headings: GettingStarted, The Channels, The Birds,Satellite TV Programming, TheDish, Satellite TV Receivers andTuning In.


Rush Wire Strippers announcesa 4 -page brochure describing themodel RW-3A hand -operatedmulticonductor cable stripper.

The brochure includes technicaland application data for this modelthat is designed to remove boththe outer jacket insulation and theinsulation from inner conductorsof multiconductor cables in oneoperation.


Contact East is offering a free,one-year subscription to its latestTool and Instrument catalog thatlists more than 5,000 hard -to -findproducts for assembling, install-ing, testing, and repairing elec-tronic equipment. Orders to thiscompany are shipped within 24hours.


Products and materials for pro-tecting microcircuits against staticelectricity damage in production,shipment and use has beencatalogued by Wescorp.

The catalog includes photo-graphs and specifications of wriststraps; protective systems, ship-ping, storage and handling equip-ment; ionization systems; detec-tion instruments; and floor andbenchtop covers.


A coaxial cable and accessorycatalog has been released byL-COM Data Products. Listed are450 line items composed of ready-made coaxial cables with molded -on connectors; BNC, TNC, "N,"UHF and Twinaxial.

Also included are many types ofcoaxial adaptors, compact coaxialtransfer switches, cable testers,wall plates and many accessories,plus a series of rack panels thatallows a variety of coaxial cabletypes to terminate and to bepatched at will.

All items listed are regarded asstandard types and are usuallyavailable from stock.

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Electronic Servicing & Technology 55

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Editor's note: Periodically Elec-tronic Servicing & Technologyfeatures books dealing with subjectsof interest to our readers. Pleasedirect inquiries and orders to thepublisher at the address given,rather than to us.Analog Printed Circuit Design& Drafting, by Darryl Lindsey;Bishop Graphics; 430 pages;$149.95 hardbound, includesbinder of drafting aids pricedseparately at $99.95.

The author teaches the in-tricacies of analog printed circuitdesign and drafting by havingreaders create PCB design andartworks. There also is a thoroughexplanation of schematic dia-grams, an in-depth description ofcomponents and PC board packag-ing, and an analysis of PCB designconsiderations. Self-help quizzesand tests appear, variously, at theend of each chapter.

For a free bulletin detailing in-formation about this book, contactthe customer service departmentof the publisher and requestBulletin No. 5008.Bishop Graphics, P.O. Box 5007, WestlakeVillage, CA 91359.

Electronic PrototypeConstruction, by Stephen D.Kasten; Howard W. Sams &Co.; 400 pages; $17.95paperback.

Anyone interested in andinvolved with electronics will findthis book easy to read and full ofpractical information for convert-ing schematics and ideas intofunctional electronic prototypeunits. Four major categories ofprototype construction arepresented: wire -wrapping, printedcircuit boards, graphic techniquesand hardware packaging. Variousfacets of the categories arediscussed, together with specifictools, equipment and techniquesrelevant to each. All of theconstruction areas necessarilyoverlap, but each section isdefinitively organized, withsometime -novel approaches aimed

at simplifying construction andminimizing the need for expensiveequipment. Because one bookcannot cover such a wide subject,there are numerous references toother resources.Howard W. Sams, 4300 W. 62nd St.,Indianapolis, IN 46268

Most -Often -Needed 1926 to 1950Philco Diagrams and ServicingInformation, compiled byKristina H. Beitman; ARSEnterprises; 177 pages; 8'/2x11format, $17.

This latest in the long line oftechnical service manuals pub-lished by Supreme Publicationssince the 1930s (Supreme is nowpart of ARS Enterprises) coversmost Philco sets that collectorsand repair shops are likely to en-counter-more than 250 Philcomodels and chassis.ARS Enterprises, P.O. Box 997, Mercer Island,WA 98040.

Linear and Interface CircuitsApplications, Volume 1, by D.E.Pippenger and E.J. Tobaben;Texas Instruments; 140 pages;$11.95 paperback.

With the computer age as an im-mediate sequel to the technologyof the single integrated circuitchip, a broad range of integratedcircuits has been developed thatcan be divided into two generalclasses: logic and non -logic. Thisbook is the first of a series that ad-dresses the non -logic devices.

Volume 1 discusses operationalamplifiers, comparators, videoamplifiers, voltage regulators andtimers. Information on displaydrivers and data line drivers,receivers and transceivers will bepresented in Volume 2; Volume 3will inform readers aboutperipheral drivers, data acquisi-tion circuits, and special functions.

The books have been divided intobasically independent sections,with each section covering a prod-uct category that begins with thebasic theory of that product,followed by the key characteristicsand applications of correlativedevices. Circuit examples havebeen selected from numerouscustomer inquiries and relatedlaboratory simulations.Texas Instruments, P.O. Box 225474, Mail Sta-tion 8218, Dallas, TX 75265.


Desoldering handpumpsNow available from A.P.E. Cor-

poration is a complete line ofdesoldering handpumps: ModelDP -1 is all -metal construction,with anti -static tip; model DP -2 isanti -static and conductive withconductive tip; model DP -3 is alarge capacity plastic constructiondesoldering device; model DP -4 is

/loi01-000.r,41.00 _..rr

spring actuated on the return andis all plastic; model DP -5 is springactuated, conductive and anti-static with anti -static tip.


Desoldering braidPhilips ECG, a subsidiary of

North American Philips, has in-troduced Swiftwick desolderingbraid, available in 5- and 25 -footlength spools. The five most popu-lar widths range from 0.03 inches

for fine desoldering to 0.13 inchesfor heavy desoldering jobs. Thespool labels are color coded foreasy identification of five sizes.

Swiftwick is a sensitive copperbraid produced through a patented

vacuumization process that yieldsa high-speed reaction wick. It isrecommended by the company foruse in all solder removing opera-tions whether delicate, intricate orroutine.


41/2 digit hand-held DMM4. W. Sperry Instruments an-

nounces its model DM -7010 41/2digit DMM, which features ninefunctions on 33 ranges, with basicdo accuracy of 0.05% of reading.

i3ooL.

211.1 nee.

1«211.'

be. 44.160. 100

-44- >10 na <

.1000

nr=, terr mm

o iee. MegiA'G',10A A COM vie

O O O .,.., O

AWS 0111-7010

Other features include a maximumdisplay of 19999, ac/dc currentfunctions, resistance and conduc-tance capability, diode and con-tinuity tests, frequency counter upto 200kHz, overload protection onall ranges, safety designed inputjacks and a built-in tilt stand.


Wireless home videotransmission

Wawasee Electronics introducesthe model JB700 wireless homevideo transmission system that ac-cepts all raw audio -video signal in-puts from a VCR, video camera orsatellite receiver and convertsthem to the VHF TV band channel2 to 6 for wireless relay to othertelevisions in a home.

No extra channels are required;the need for A -B switches andcable installation is eliminated.Preset station is channel 6; useroption available of 2 to 6 channels.

The unit is used to transmit TV

prksPocket-

8 SizeSoldering

Safe, no open flame. Only 7 inches long. Adjustable, with

10-60 W power. 3 tip sizes. No cords or

batteries. Runs 60 minutes

on one refill. Heats and cools

in seconds.

Portasol is the firstbutane -powered,portable soldering ironthat's safe, convenientand economical. Notmuch larger than a feltmarker and as easy to

use as a cigarettelighter, Portasol is

the ideal toolfor solder-

ing anddesol-

ae,dering

in tightspots or

where noelectrical

outlets areavailable. And

because it'sstatic free, Portasol

is ideal for use withCMOS and other

static -sensitive com-ponents.

See the flameless.static -free Portasolsoldering iron at yournearest Boardworkselectronics supplydealer. For the locationof the Boardworksdealer nearest you, callor write to:

The Boardworks1077 E. Edna PlaceP.O. Box 1678Covina, CA 91722Telephone (818) 967-3681

Circle (181 on Reply Card


Full -featuredfrequency

counter.The DM850 offers more than any

digital multimeter in its price class:

41/2 digits. DCV accuracy is.05% + 3 digits

'flue RMSFrequency counter to 200KHzData Hold display capabilityDCV-5 ranges (.2V to 1kV)ACV -5 ranges (.2V to 750V)DCA/ACA- 6 ranges (.2mA to 10A)Ohms -6 ranges (200 Ohms to

20 Megohms)Continuity beeperDiode checkBuilt-in bailAnti-skid pads

Prices: DM850 (Due RMS) ... 521995*

DM800 (Average RMS) . 816995*

See one now at your local BeckmanIndustrial distributor.

Dr,l ..O\D

CIFICUITMATE DM350

with battenv, test lend, and manual.

.tu -e- u

Beckman Industrial CorporationA Subsidiary of Emerson Electric Company630 Puente Street, Brea, CA 92621( 714) 671-4800

e Copyright 1985 Beckman Industrial Corporation

signals to remote TV locationsthroughout the home without us-ing a coaxial cable system todeliver the signals. It comes com-plete with plug-in cables andtelescope antenna.


Hot tweezer toolSurface -mounted components

can be removed quickly and safelysays Plato by using Hot Grips. Awide selection of interchangeable

tools is available to desolder chips,SOICs, SOTs and quad -packs.Regulated temperature, ergo-nomically designed hand piece,rapid heat -up and spike -free opera-tion are all features of this hottweezer tool.


Temperature recording labelsCelsiDot single level tempera-

ture -sensitive labels now areavailable on rolls with 1,200 piecesof identical dots. There are 40 dif-ferent temperature ratingsavailable between 105°F (40°C)and 550°F (260°C). The original

white temperature -sensitive in-dicating triangle will turn per-manently black when exposedabove its rated temperature level.

The self-adhesive labels fromSAT, a Spirig company, can be ap-plied to any clean, dry surface tomonitor safe or unsafe tempera-tures reached during practical usewithin hours, days, weeks or yearsfollowing application. A blackeneddot will document that equipmenthas been exposed above itsspecified temperature level.


3 -Channel oscilloscopesIwatsu Instruments has an-

nounced two new delayed -sweeposcilloscopes that feature accuracyof ± 2% for vertical and horizon-tal deflection with a CRT ac-celerating voltage of 12kV, allow-ing easy viewing of high-speedsignals and signals of slow repeti-tion and fast rise time.

i

3 ;`..

r¡ieQ ..+!'-. Ah': oare ` ' ame. ..oh, ! '®_41,211 S! V 0_ I"

Both the SS -5706 30MHz andSS -5705 40MHz oscilloscopes offer3 -channel inputs for simultaneousdisplay. Each channel is equippedwith an independent position con-trol to increase measurementrange. The SS5705 also incor-porates alternate sweep, so thatthe enlarged waveform of adelayed sweep can be displayedsimultaneously with the originalwaveform, up to six traces.


SMD Test TWEEZERSTwo SMD Test Tweezer clips for

surface -mounted devices havebeen designed by ITT PomonaElectronics. Model 5143 featurestwo single stacking banana plugsas the terminal end. Model 5142features a BNC male connector.

Both SMD Test Tweezer clipshave a conductor in each leg en-abling the user to test at the sametime both sides of a surface -

mounted device. These nylontweezers are fitted with goldplated beryllium copper contacts;they permit testing surface -mounted devices whether thedevices are loose, on a circuitboard or on a reel.

Circle (82) on Reply CardCircle (22) on Reply Card


Continued from Page 43

"Eliminator" will spot such thingsas open fuses, surge resistors, badfilter capacitors, shorted LVrectifiers, open LV regulatordevices, defective LV regulator drivecircuits, shorted or open horizoutput devices, bad damper diodesand safety capacitors, shorted pincushion transformers, yokes,discharge capacitors in the horizyoke circuit, centering diodes,shorted horiz driver transistors,shorted oscillator stages, open horizosc / driver stages, defective startup circuits, shut down circuits, andscan derived B + circuits, (withregards to shorted rectifiers andassociated filters in scan derived B +circuits, the "Eliminator" will tellyou specifically which circuit(s) areconnected to the shorted scan B+winding).

If the resistor is open that couplesthe secondary of the horiz drivertransformer to the base of the horizoutput, the "Eliminator" will tellyou so.

If the scan derived B+ circuit isopen that feeds the horiz osc anddriver stages, the "Eliminator" willtell you so.

If the vertical output circuit is eitheropen or shorted the "Eliminator"will tell you so. The same goes forshorted red, green, and blue, videooutput transistors.

If the CRT is developing a secondanode short when it gets hot, the"Eliminator" will likewise tell youso.

Nothing, - - - absolutely nothing,no amount of other test equipment,no quantity of technicians, and nopossbile combination of the abovecan compete with just one"Eliminator". It can't be done!If you so desired, you could nodoubt cut you present labor rates inhalf, work only a fraction of yourpresent hours, simultaneouslydouble your production output, andat least triple your present netprofit, with just one "Eliminator".

You could place an ad in the paperor on TV that states "Bring yourcolor TV repair job in for a genuinecomputer diagnosis, and anaccurate estimate, for a total cost ofonly ten dollars. With our newcomputer, we can repair your colorTV set for about half of the normallabor rates". (We are not recom-mending this).

ADVERTISEMENT

In the race between discount chainstores and their ever decreasing costof replacement equipment, you (notthem) will now be able to competefor the purchasing power of today'sconsumer. The best part is, Y O Ucan make some really big moneywhile THEY try (for a change), tofind some way to compete withY O U!! Unless the TV set has a badCRT, flyback or yoke, they won'tbe likely to find such a way, short ofpassing their new TV sets out asignificant loss!

It should come as no surprise whywe have chosen to name our newcomputer the "Eliminator"!

The "Eliminator" is a full fledged,bonified, total logic, decisionmaking computer that carries a100% two year parts and laborwarranty (except for physicallyobvious abuse, and cosmetics). Ifyou can find a way to tear it up, wewill repair it free of charge. You payonly for transportation.

IMAGINE THIS:A TV set shows up in your shop.You plug it into your computer,press one button and a red lightcomes on in back of the verticaloutput circuit in the block diagramof the computer's display panel. Injust one second, without so much asremoving the back of the TV set,you know where the problem is.

Generally speaking, red lightsindicate shorts, yellow lights meanthat an open circuit exists.Another set shows up. You plug it inand the surge resistor in the LVsupply of the block diagram is lit upyellow. You replace the surgeresistor and push the test buttonagain. This time the LV rectifier inthe scan derived B + supply for theR, B, G video outputs is lit up red.You replace the LV rectifier, pushthe test button, and presto! The setnow has a picture on it! It's fixedand ready for the cookout bench.After pushing the test button for thenext set, a red light comes on behindthe LV rectifiers. In another the HVmultiplier is lit up red.

Later in the same day, the start upcircuit is red for one set, another TVset comes in with a color picturebut, the shut down stage in theblock diagram is red.

In fact, any problems in any of thepreviously mentioned long list ofcircuit failures will be displayed ineither yellow or red on the screen ofyour "Eliminator" when and if they

fail. In many instances, if yourcomputer sees two or moreproblems at the same time, it willsimultaneously display both.It may sound like the "pipe dream"of some technician turned "madinventor", but, we are alreadymanufacturing them, and they doexactly what we have stated. If youwould like to own either a Mark VI,Mark VII or the "Eliminator"(which is an add on, plug incomputer for the Mark VII unit),you can bet your socks that we havea dealer in your area who would liketo show you one in operation. If wedon't have, we very soon will!Without actually seeing one in use,it's impossible to imagine everythingit will do. We used to sell via directmail, but, when we decided torelease the "Eliminator" werealized the necessity of local dealerswho could demonstrate it "handson".For this reason, we have chosen TVservice shops or technically qualifiedparts wholesalers to sell ourproducts.

Yes, we still manufacture our MarkIII and Mark V computers foranalyzing horiz / hi -voltagecircuits. For those who already havea Mark III or V unit, the Mark VI orMark VII will certainly complimentthe operation of either unit. Amember of our design team recentlystated, "Owning a Mark III is likebeing released from a set of life longshackles. Getting a Mark V was likehaving the same shackles removedand being permitted to use handtools for the first time. Buying an"Eliminator" is just like having theworld's greatest technician come towork for you. Then, realizing thathe also owned a magic wand."If you would like a "hands on"demonstration, and are willing todrive fifty or so miles to get one, call(806) 359-0329, or write to theabove address asking for same. Wewill be pleased to give you the name,address and phone number of yournearest sales dealer.Your local dealer will do "handstands" for a chance to show youour test equipment in action. But beaware that in most cases, you willhave to go to his shop for a "handson" demonstration. Please keep inmind that he is not only your salesdealer, he also has a TV repairbusiness to run. Even so, who couldbetter demonstrate test equipmentthan the people who are using it on aday to day basis! The drive to hisshop will be more than worth thetime.

ADVERTISEMENTCircle (12) on Reply Card

Test

your electronicknowledge

1. To reproduce a glitch, anoscilloscope must have a verticalamplifier that hasA.) a very high gain.B.) a very wide bandwidth.C.) no phase inversion.D.) de amplification.E.) no feedback.

2. Anything you do to increasethe gain of an amplifier willautomatically decrease itsA.) noise.B.) distortion.C.) cost.D.) phase shift.E.) bandwidth.

3. Which of the following is amethod often used to increase thebandwidth of an amplifier?A.) Decrease its power supplyvoltageB.) Increase its gainC.) Use degenerative feedbackD.) Use regenerative feedbackE.) Introduce white noise

4. For an operational amplifier(like the one in Figure 1), the band-width would be increased byA.) increasing the resistance ofRL.B.) decreasing the resistance ofRL.C.) increasing the resistance ofR,.D.) Decreasing the resistance ofR,.E.) (None of these choices is cor-rect.)

By Sam Wilson

5. Which of the following has thegreatest frequency stability?A.) Wideband amplifiersB.) Narrowband amplifiersC.) OscillatorsD.) Any amplifier with regenera-tive feedbackE.) Medium bandwidth amp-lifiers

6. A graph showing the gain ofan amplifier over the range of fre-quencies it is designed to cover iscalledA). a Fourier analysis.B.) a stability plot.C.) a peaking graph.D.) a gain graph.E). a Bode plot.

7. If a graph shows amplifier out-put power over a range of frequen-cies, the bandwidth of theamplifier is measured at theA.) maximum frequency point.B.) maximum amplitude point.C.) frequency range between thepoints where the curve drops to70.7% of maximum.D.) - 6dB points.E.) points where the output is50% of maximum.

8. Technicians must be carefulnot to confuse low -frequency com-pensation in an amplifier circuitwithA.) decoupling filters.B.) peaking compensation.C.) load resistors.D.) regenerative feedback.E.) noise generators.

9. Which of the following types ofcoupling is best for the verticalamplifier section of anoscilloscope?A.) TransformerB.) ImpedanceC.) R -CD.) DirectE.) Link

10. Which of the following is aproblem with direct -coupledamplifiers?A.) Poor gainB.) Level shiftingC.) Loss of low frequenciesD.) NarrowbandE.) 180 ° phase shift


Answers to the Quiz

1. B. A glitch is a short -durationpulse that is rich in harmonics. Awideband amplifier is needed forreproducing the harmonics and,thereby, reproducing the rapid riseof the glitch.

2. E. In the past, there have beensome letters about this. However,the statement generally is true. Itassumes that you have a workingclass -A amplifier.

3. C. Degenerative feedback,which is also called negative feed-back, reduces the gain and in-creases the bandwidth of an

amplifier.

4. D. When R, is decreased thegain is reduced. That, in turn, in-creases the bandwidth.

5. A. High -gain, narrowbandamplifiers are more unstable. Anoscillator is a very high -gainamplifier with a very narrow band-width.

6. E.

7. E. This is one definition ofbandwidth.

8. A. Both circuits look the same.

However, decoupling circuitsusually have a shorter time con-stant.

9. D. Assuming the circuit isproperly designed, a direct -coupled amplifier has a very widebandwidth.

10. B. With direct -coupledstages, each successive amplifierrequires a high voltage for itsoperation. In bipolar circuits, anNPN amplifier is followed by aPNP type to shift the de level.Another method used is to have anemitter follower inthe output. AWL

Vs40010,

MARCHProtecting against static electricity damage-Static electricity of a potential far lower thannecessary to cause your clothes to cling or tocause a snap when you touch the faucet isenough, if discharged through a static -sensitivedevice, to destroy it. This article reviews thereasons why devices have become increasinglystatic sensitive, suggests easily followed pro-cedures to minimize ESD damage, and dis-cusses some of the products that are availableto inhibit buildup of static electricity or drain itaway as it builds up.

Servicing the Commodore 64-Starting with areview of the circuit design and theory of opera-tion, this article takes the reader on a guidedtour of the Commodore 64 personal computer,including suggested troubleshooting steps. Anespecially valuable feature of this article is adescription of the symptoms observed aftereach major component was removed from thecircuit.

Power protection for electronic equipment -Ahigh-energy spike on your ac power line candisrupt the operation of sophisticated elec-tronics equipment, or even destroy components.Other power line perturbations like sags, surgesand electrical noise can impair the operation ofelectronics products. This article describes thenature of these power -line problems and sug-gests ways to combat them.

What do you know about electronics? - Capaci-tors and triggers. A Schmitt Trigger is a valuablecircuit for two reasons: It provides abrupt transi-tions between its two output states and it ex-hibits hysteresis, which makes it stable in eitherstate. Sam Wilson gives details about the opera-tion of this valuable, interesting circuit, andruminates about capacitors and transistorparameters.


Readers' Exchange

For Sale: Tubes-new 6AC7, 6B45, 6H6, 6SR7, 6X5, 35A5; L octalspretested, 6A8, 7B7 (two), 14AF7, 50X6; octals pretested, IA7, 5W4, 6C5(two), 6K6, 6N7, 6SA7 (two), 6SK7 (two), 6SL7, 6SW7 (two), 6SQ7 (two),6SS7, 6X5 (two), 12A8, 2SW4 (two), 2S26; extras included, 1W 41-78(two), 6F7. $50 plus shipping, c.o.d. M.E. Andrews Jr., Box 91, Exeter, RI02822.

Wanted: Service literature for KLH model 27 tuner amplifier. Will copyand return or pay for copy. Jim Geier, Box 341, Ketchum, ID 83340.

Needed: Flyback transformer for Broadmoor TV model 3513, part No.0927076M or TCF-11. Please state price. George Saylor, 2319 Parrish St.,Philadelphia, PA 19130.

For Sale: Sams Photofact folders 601 to 999 and assorted others. Mustsell, $1 each; digital capacitor meter with power transformer and a VTVM,$125 or will trade for a DMM and a subtuner. David Muratore, 27Clarkview Road, New Windsor, NY 12550; 914-562-2805.

For Sale: 300 new radio and TV tubes, $150 plus shipping. All are inoriginal cartons except a few of the older radio tubes. T.W. Benson, 204Riverside Ave., Tallassee, AL 36078; 205-283-4266.

For Sale: Various makes of multimeters, $10 to $75, send for lists; EICOmultisignal tracer model 145, $35; Jackson TV signal generaor modelTVG2, $35. Payable in U.S. funds plus postage, or by money order. Nochecks. Ed Barlow, Box 29, Tweed, Ontario, Canada KOK3J0.

For Sale: Monsanto timer -counter model 100A, $75; signal generator byLAB -VOLT, model 710, solid-state, $50; color -TV parts, including picturetubes, all in perfect condition. Gary Barzily, 84-39 120th St., Jamaica, NY11415.

For Sale: Sencore VA48, like new, $650. M. Burkhard, 21440 IglesiaDrive, Woodland Hills, CA 91364; 818-347-3748.

Wanted: Books or manuals dealing with electrical aspects of neon sign con-struction and shop equipment. Will pay reasonable price. Steve Mashburn,Route 3, Box 393-H, Muskogee, OK 74401; 918-687-1108.

Wanted: Sams out -of -print "Transistor Circuit Design," by Oklee. John H.Stephens, P.O. Box 168, Wickes, AR 71973.

For Sale: 450 new receiving tubes; 700 used receiving tubes; used and newyokes and flybacks; ES&T schematics, 1970 to 1985. $600 for all. JerryFinkel, 4924 NW 54th Court, Ft. Lauderdale, FL 33319.

For Sale: Panasonic and Quasar service manuals, 1200 + , with 1985 sup-plements (bought out former Panasonic distributor). Included are manualsfor televisions, microwaves, receivers-from foot warmers to hairdryers-plus some VCR and video camera manuals, and 15 binders valuedat $200. All, $500 plus shipping. Cyril Brennan, 661 Horseshoe Curve, PikeRoad, AL 36064; 205-277-0139.

For Sale: EICO model 950B bridge, $35; DM6013 digital capacitancemeter, $45; prices plus shipping and COD All instruments in excellent con-dition, and with leads and manuals. Ronald Kolasa, 4942 E. Flower Ave.,Mesa, AZ 85206.

Wanted: Conar model 400 Novice transmitter, model 500 Novice receiverand Conair model 215 digital multimeter. William P. Jarvis, 1214 FifthAve., Beaver Falls, PA 15010.

Needed: Schematics and service manual, or information, for the Panasonicopen reel-to-reel helical scan videotape recorder model NV3082 and itscompanion video camera WV3082. Robert C. Pease, Bob's Electronics, 340E. Fourth Ave., Stanley, WI 54768; 715-644-2557.

Wanted: Flyback transformer for Admiral color television, part No. 79A187-1, chassis No. M10. Used, fair price. Sams Photofact folder 1477,reasonable price. L.H., 4366 Eastport Drive, Bridgeport, MI 48722.

Needed: Servicing literature for amplifier-Analog (AEA) A610 poweramp. Schematics and service manuals, or any information, welcome; thecompany is out of business. Norman D. Thompson, 141 Crystal Lake Road,Middletown, CT 06457; 203-284-4082.

Needed: Supremes TV -1, TV -2 and R-1 manuals; Simpson 269 and 260,series -6 manuals. C. T. Huth, 229 Melmore St., Tiffin, OH 44883.

For Sale: VIZ Senior Voltohmyst model WV98C, like new, $100 or best of-fer; new 8060 Fluke, 4112 -digit with frequency measurements, true rms, dB -referenced, resistance measurement to 300M and other features, neverbeen used, $295. Prices plus COD, insurance and shipping. StanleyTodorow, GG8468 Belle Bluff Drive, Grand Blanc, MI 48439.

For Sale: B&K 1076 TV analyst, B&K 960 transistor radio analyst, RCAWO -535A oscilloscope. All are complete with manuals and test leads. $350for all, I will pay shipping. Free B&K 350 CRT checker with purchase.David Lehmann, RR2, Box 104, Mansfield, MO 65704; 417-924-3350.

For Sale or Trade: Regulated power supply, Heathkit model HWA 202-1,with output to 2.2A at 13.8V, ac input, can be wired for 120V or 240V, uses3 -wire grounded line cord, good condition, with manual, $25; commercialcable system AM -FM receiver, Cablenet model 4033A, has 75 input, worksgreat, $7.50; H.F. transceiver, Heath HW-101, covers 80m to 10m,CW/SSB, with power supply, CW filter, SSB filter and manual, output100W, with special Swan vernier main tuning knob, $125. Other items toonumerous to list, send s.a.s.e. Mike Adams, Able TV and Electronics, 6333Highway 2321, Panama City, FL 32404; 904-785-7824.

Wanted: Magnavox AM -FM integrator, part No. 250564-1, new or used.A.S.R. TV Service, 199-05 32nd Ave., Bayside, NY 11358; 718-352-5078.

For Sale: NRI basic and advanced CB Communication Course, and NRIAudio Servicing Course that includes a trainer and electronic componentsfor experiments, $150; Simpson model 465A autoranging digitalmultimeter, $200; 41 Sams CB service manuals, $100; B&K model PR28high voltage multiplier probe, new, $18. All, excellent condition, with usualinstruction manuals. Clarence G. McKee, 9516 Zion Road, Rives Junction,MI 49277; 517-569-3139.

Wanted: Sams Photofacts folders, 1400 to 2000. Ray Brumbaugh, 118Kaywood Drive, Statesville, NC 28677; 704-872-5742.

Wanted: Schematics or service manuals for Radio Hallicrafters modelS408, Zenith TV model 14DC15, Zenith radio ch. 5E6OBT. State price.Ram TV Service, San Vincente 4E, Mayaguez, PR 00708.

For Sale: Sencore TF-151A transistor, FET tester, $85; EICO 944flyback, yoke tester, $15. All, good condition, with manuals. BobHogaboam, 7445 Chesterfield Road, Pensacola, FL 32506; 904-455-5587.

Wanted: Complete kit of alignment tapes and mechanical jigs for servicingVHS VCRs. Also looking for NTSC generagto and a wow -and -fluttermeter. Reasonably priced. Dave's Stereo and TV Service, 111 Fourth St.,Fulton, IL 61252; 815-589-4662.

Wanted: B&K 747B tube tester in good condition. C. Mott, Box 222, MobilLand Court, Bloomington, IL 61701; 309-828-3515.

Needed: General radio manual 1710-0100 for 1714 system power control,1711 tracking sweep generator, 1713 parameter and 1712 tracking detec-tor. Bill Janton, Computer Technology, Flowing Wells High School, 3725 N.Flowing Wells Road, Tucson, AZ 85705.

Wanted: Half-track or stereo playback for American Concertone model505E reel-to-reel audio tape machine. Don Setliff, Don Setlif jrRadio, RouteNo. 1, Box 237A, Apple Grove, WV 25502.

For Sale: Model SG165 Sencore, like -new condition, $795, will pay ship-ping; two Sony picture tubes No. 470FWB22 and 330AB22, $80 each.Robert F. Nestor, 3407 Arlington Ave., Riverside, CA 92506; 714-684-9393.

Wanted: Schematics and/or operating instructions for Commercial TradesInstitute model TC-20 tube checker and EICO model 625 tube tester. M.E.Carney, RD No. 2, Box 139, Bridgeton, NJ 08302.

Wanted: Capitol Radio Engineering Institute's Engineering Mathematicsprogram No. 270. Reasonably priced. D.M. Merritt, 29911 Mira LomaDrive, Apt. 2, Rancho, CA 92390.

Wanted: For Bohsei TC-700 13" color television-doubler, part No.2459-002-010; flyback, part No. 2859-000-0202. Scott Winter, 572 CentralAve., Needham, MA 02192; 617-787-3510 (days), 617-149-4893 (evenings).

For Sale: VA48, used only once. Complete with instructions and in originalbox. Make offer. William J. Maida, 274 W. Sabal Palm Place, Longwood,FL 32779.

For Sale: EICO model 944 flyback and yoke tester, unused, $30; EICOmodel 495 scope voltage calibrator, $20; Hickok model KS -15750-L1 tubetester, $100. Send certified check. N. Young, 214 E. Robertson St., Bran-don, FL 33511.

Wanted: New 455kHz miniature tube IF transformers-Zenith 95-1505,J.W. Miller 16-PC5, 12-C7, 14-C1, kHz455, GE M76J37-10. Also, Miller7702-Z, etc. 14 -pin IC F706APC. Manuals for Hickok tube tester model533A, and Heath DX -20 transmitter. WB2IQE Rock Radio, J.R. Fickeisen,5014 Skinner Hill, Moravia, NY 13118; 315-497-1480.


Photofact folders for TV receivers and computers releasedby Howard W. Sams since ES&T's last report.

MAGNAVOXRE4042WA01 2379-1

MITSUBISHICS -1304 2381-2

PHILCOChassis 13C501, 13C502 2380-2

SEARS564.49050450/451 2382-3

CITEK SHARP7495A, 7498A 2380-1 20J650 2377-1

CITEK SONY7494 2382-1 KV1976R (CH. SCC-548R-A) 2378-2

CITEK/TEKNIKA TOSHIBA5579/3579 2376-1 Chassis TAC8336 2379-2

CITEK/TEKNIKA WARDS5589/3589 2378-1 GNB12894AIB/C 2377-2

2382-2

2381-1

GOLD STARCMT-2515

KTVKCT 1300

COMPUTERFACTS

RADIO SHACK TRS80MAGNAVOX Model 26-3002 CC13Chassis 19C106-00AA/107-00AA/109-00AA/

111-00AA/115-00DA/116-00AA/119-00AA/ STAR121-00CA 2376-2 Model Gemini -15X CP16

ClassifiedY V Y AA",Y

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For ads on which replies are sent to us for forwarding(blind ads), there is an additional charge of $25.00 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 SALEAUTOMOBILE RADIO and tape replacement parts.Delco, Chrysler, Philco-Ford. Motorola, Panasonic andmany others. Large inventory. Laran Electronics, Inc.,3768 Boston Road, Bronx, NY 10469. (212) 881-9600.National (800) 223-8314, NY State (800) 446-4430.

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BOOTLEGGERS BIBLE for CB Modification $12.95, CBRadio Repair $10.95. Linear Amplifier Planbook$14.95, kits, etc. Catalog $1.00 refundable-APS, POB263 Newport, R.I. 02840 401-846-5627. 12-84-tfn

SCRAMBLED TELEVISION, encoding/decoding. Newbook. Theory/circuits, $9.95 plus $1 shipping. Work-shop, Box 393ES, Dept. E, Bethpage, NY 11714.

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TV TROUBLE ANALYSIS TIPS. Over 300 symptoms/remedies by circuit area; tough ones over the years.Save time and money. Send $12.50 to CHAN TV, 8151Grandview Rd., Chanhassen, MN 55317. 1-85-tfn

MAKE TELEPHONE answering machine servicingsimple & professional. Without tying up your phonelines, our ring simulator will activate any machine onthe market. You can hear the outgoing message, giveyour message, and also have the availability to checkmachines that have remote capability. Send yourcheck for $85.00 made payable to PSI, INC, to covercost of machine shipping and handling or call (201)845-6669. PSI, Inc. is located at: 34, Route 17 North,Paramus, New Jersey 07652. 4-84-tf n

CABLE CONVERTERS. Lowest price. Dealer inquiriesaccepted. Quantity Discounts. FREE CATALOG. P.G.Video Corp, 61 Gatchell St., Dept. ES&T, Buffalo, NY14212. 5 -85 -tin

REPAIR OF ZENITH circuit board 9 -160 -all; with dudexchange $33.00. One year guarantee. Kinirral Elec-tronics, 68-26 64th Place, Glendale, N.Y. 11385, (718)366-3859. 12-8-5-3t

SANYO HORIZONTAL OUTPUT TRANSISTOR2SD1341, $1.99 plus other name brand transistors,IC's, RF-Power, Sanyo rechargeable batteries andLED's. For best buys plus service call 1.800-458-6053.PA call 1-800-672.7100. M/CNISA honored. Savings,service, quality. At B&D we do it better. B&D Enter -prizes, Box 305, Kane, PA 16735. 1-86-2t

HEWLETT PACKARD 333A Distortion Analyzer $495.B&K 801 cap analyst $60.00. Both mint, pricesnegotiable. Konney, 2519 N. Austin, Chicago, 60639.312-237-7845. 2-86-1t

SONY-TRINITRON REBUILTS are now available. Callfor price & delivery. 1-716-621.5250. 1-86-2t

CABLE TV CONVERTERS & EQUIPMENT. Plans andparts. Build or buy. FREE information. C&D Elec-tronics, P.O. Box 1402, Dept ES&T, Hope, Arkansas71801. 1 -86 -tin

INDIVIDUAL PHOTOFACT FOLDERS (Not sets) #1 to#1400. $3.00 first-class postpaid. Loeb. 414 ChestnutLane, East Meadow, NY 11554. 1-86-3t

HELP WANTEDCAMERA -VIDEO Technicians needed. Top pay andbenefits for well trained and experienced technicianswho are expert with consumer and/or industrialcameras and VCR's. Training by manufacturers suchas Sony, Hitachi, Panasonic, etc., are necessary forjob experience. Come to sunny Florida and enjoy yourwork & leisure time. Write or call ATLANTIC ELEC-TRONICS INC., 1881 NE 26 St., Ft. Lauderdale, FL33305. (305)564-8274 10 AM to 6:30 PM. Ask for Dave orJoe. 8-85-tfn

BUSINESS OPPORTUNITIES3 HOURS FROM SAN FRANCISCO! Town of paradisein pine forested foothills. Electronic repair business.Building/shop/equipment/7 room residence with largegarden. $165K, (916) 872.1962. 12-85-tfn

SELF DESIGNERS, Investors, and Electro-Hobbistswe offer you our Complete Home Robot DesÍpns Eclusively from Cad Design services. rui yu,,,and listings of other current designs, send a check ormoney order for $5.00 to: CAD Design Services, P.O.Box 1192, Jackson, MI 49204. 1-86-2t

TV REPAIR SHOP Well established. Located in rapidlygrowing Phoenix area. Nets $60K+. Owner will carrywith substantial down. VR Business Brokers, 935 E.Main St., Mesa, AZ 85203, Phone (602)833-8923. 2-86-1t

MID COAST MAIN Electronic repair shop for sale.House, shop,, van, and all equipment $84,000. Call orwrite Dolphin Electronics, Route 90. West Rockport,ME 04865, 207-236-9074. 12-85-2t

UNIVERSITY DEGREES Economical home study forBachelor's, Master's, Doctorate. Prestigious facultycounsels for independent study and life experiencecredits. Free information - Richard Crews, M.D. (Har-vard), President, Columbia Pacific University, 1415Third St., Dept. 2882, San Rafael, CA 94901; Toll Free:800/227-0119; California: 8001552.5522; or415/459-1650. 2-86-1t


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In our continuingefforts toserve you...

From time to time, Intertec PublishingCorp. makes its subscriber listsavailable to carefully screenedcompanies or organizations whoseproducts, services or informationof interest to you. In every case, listusers must submit their promotionalmaterial for approval. They may uselist only once.

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Advertisers' Index

Automated Production Equipment

PageNumber

ReaderService AdvertiserNumber Hotline

Corp. 51 14 . - .. 516/654-1197

B&K Precision, Dynascan Corp. 21 19 . ..312/889-9087Beckman Industrial Corp. 58 22 .... 714/671-4800

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Cleveland Institute of Electronics ...16,17 6 800/321-2155

Cleveland Institute ofElectronics 16A -16B 800/321-2155

Cooper Group 3 4 919/362-7510Dandy Mfg. Co. 64 24 .... 800/331-9658Diehl Engineering 19,43,59 12....806/359-0329Digitron Electronic 47 13....800/526-4928E -Z -Hook IBC 2 818/445-6175Edsyn Inc. 53 20....818/989-2324ETA 56

Leader Instrument Corp. IFC 1,21 ..516/231-6900MCM Electronics 23 8 . ... 800/543-4330NATESA 56

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Optima Electronics 27 10 .... 800/327-0224Pace, Inc 9 5 301/490-9860Philips ECG 15 17 .... 800/225-8326Projector Recorder Belt Corp 55 15....800/558-9572Sperry AW Instruments Inc 1 3 800/645-5398Sperry Tech, Inc 64 23 .... 800/228-4338Wahl Clipper Corp 39 11....815/625-6525Zenith BAC

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Go for 'em! Solid margins year -around! They're yours in thevideo aftermarket! With this new VCR Care Kit by Zenith!

You bet there's a VCR aftermarket out there! A sizeable one. Perhapsas big as twenty million plus households. So that capitalizing onit with VCR accessories like this beautifully packaged Zenith VCRCare Kit can be very, very profitable.

Look and see for yourself!

Inside this kit, latest in a long line of Zenith video accessories -and available separately, too - are a great new VCR Head Cleaner.A T-120 VHS Blank Video Tape. A VCR Dust Cover. And a clear VHSTape Storage Cover. All proudly bearing and backed by Zenith, aname renowned for superb product performance and reliability.

They are at your Zenith distributor's place now,these new Universal VCR Care Kits, readyfor immediate delivery to heads -upservice techs alert to the moneyto be made in the overallvideo aftermarket.

t..... _..,...* .. M.r

Actually, there's more in store than ever before in this expandingline of Zenith video accessories. More than just this new Universal

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profit center right before your eyes.

So hurry! Quit second-guessing yourself! Neither this videoaccessory business nor VCR aftermarket is going to wait for you.

Call your Zenith distributor's Parts & Accessories Sales Manager!

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Zenith Service, Parts & Accessories11000 Seymour Avenue, Franklin Park,lllinois 60131

A Division of Zenith Electronics Corporation

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