IINI:Enound Repair...An up front discussion on tuner repair and module rebuilding. TV service...

EiectroMarch, 1978 0 $2.25

is servicinA HOWARD W. SAMS PUBLICATION

IINI:Enound Repair

SylvaniaHorizontal

Digital Logic

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An up front discussionon tuner repair andmodule rebuilding.

TV service technician dealersare in business to earn a profit,providing customers withtimely, professional work. Tomaximize profits and still pro-vide quality work, it makessense to take advantage ofoutside independent help. Ourtuner repair and module re-building services can add newdimension to your shop'sprofits. Consider the advan-tages PTS offers.

1. One stop shopping. Ourtuner repair service includes

all makes and models includ-ing foreign-color, black andwhite, tube, transistor orvaractor. We repair them all.Our module rebuilding ser-vices include all leadingbrands.

2. Repair . . . our firstbusiness and our majorbusiness. Our service businessisn't an after thought to manu-facturing. We stay on top ofthe latest design develop-ments in all brands-not justone or two.

3. Same day service. Yourreputation is as much time asit is quality. Same day serviceisn't a gimmick with us, it's apromise we strive to keep.

4. Module Exchange. Notonly do we rebuild modules.We also exchange and buyduds.* You can turn dudmodules into needed cash.

5. One year warranty. We'reso confident of the profes-sional quality of our work, weprovide a one year limitedwarranty to back it up.

6. Protective packages.Tuners and modules areshipped to you in protectivepackaging, eliminating risk ofdamage.

7. Replacement parts. Alltuner and module servicesutilize original or superiorparts. Parts are constantlyupdated to improve moduleand tuner performance andreliability.

8. Servicenters. There arePTS company owned servi-centers in every metropolitanarea of the U.S. Each is fullyequipped and professionallystaffed to serve you.

Acceptable brands are Admiral, GE, Magnavox.Montgomery Word, Philco, Quasar. RCA. Sylvania,Sears/Warwick, Wells -Gardner and Zenith.PTS reserves the right to reject any or all modulespresented for dud value including ceramic encap-sulated, broken or cannibalized modules.

NM. MOONONO

NO SIONIIIIMMIION

EMS

S

PTS ELECTRONICS, INC.A COMPLETE LIST OF PTS SERVICENTERS

APPEARS AT THE RIGHT.

March, 1978 Volume 28, No. 3

PTSSERVICENTER

GUIDE

MIDWESTHome 0111<

BLOOMINGTON. IN 474015233 S Hwy 37 P 0 272

817 834.9331CLEVELAND. OH 44134

5682 State Rood216 845 4480

NORTHEAST

SPRINGFIELD. MA 01103191 Chestnut P 0 3189

413 734 2737PHILADELPHIA

Upper Darby PA 190821742 44 State Rd PO 202

215 352 6609KANSAS CITY. KS 66106 PITTSBURGH. PA 15202

31I9A Merroam Lane P 0 6149 257 Revervotw Ave W P 0 4130

MINNEAPOLIS, MN 55408815-W Lake St P 0 8458

612 8242333ST. LOUIS, MO 43130

8456 Pope Blvd P 0 24256

417-761-7648E. PATERSON. NJ 07407158 Market St P 0 421

201 791 6380BUFFALO. NY 14212

993 Sycamore St P 0 1241314.428-1299 716-891 4935

DETROIT. MI 411235 BOSTON13707 W 8-Mde Rd Arlongton MA 02174

313-862 1783 1167 Massachusetts Ave P 0 371GRAND RAPIDS. MI 49501 617 648 7110

1134 Walker Northwest SYRACUSE, NY 13201P 0 1435 315N Geddes St P 0 207 Salina Stu

616 454 2754CINCINNATI OH 452168172 Vine St PC 6057

513 821 2298MILWAUKEE. WI 53210

7711 Fond du Lac414 464-0789

COLUMBUS. OH 432274005A E LoronosIon

614 737 3820INDIANAPOLIS. IN 46202

281 14th 57317 631 1551

DAVENPORT. IA 521052074E R)ver Dr P 0 187

319-323.3975OMAHA. NE 681325008 Dodge S'ree1

402 558.1800CHICAGO. IL 40645

5744 N Western Ave312 728 1800

SOUTHATLANTA. GA 30311

2180 Campbellton RoodP 0 42558

404,753 0007JACKSONVILLE. FL 22210

1918 Blanding Blvd P 0 7923904-389.9952

WASHINGTON. DCSilver Spring MD 20910

8080 IlrooluoollePd301 5650025

CHARLOTTE. NC 21225726 Semple Ave P 0 5512

704332 8007BIRMINGHAM. AL 35201210N 97651 PO 1801

705 373 2657MEMPHIS. TN 31111

361 Lamar Ave P 0 18053901 365 1918

NORFOLK. VA 235043118E Prtncess Anne Rd

804 625 2030NEW ORLEANS

%steam LA 700043920A Atrl.ne Hwy P.O 303

504837 7569TAMPA. FL 33490

2703 5 Mocdell P 0 14301813.839 5521

NASHVILLE, TN 372142426 A Lebanon Rd

615.885.0688

315 475 7330BALTIMORE. MD 212155505 Reisterstown Rd

301 358 1186

PACIFIC

SACRAMENTO. CA 95114143510 /Suborn Blvd P 0 41354

916 487 6770SAN DIEGO. CA 92105

5111 University Ave P 0 5794714 280 7070

LOS ANGELES. CA 900234184 Pooh, Woy

213 266 3728PORTLAND. OR 972135220 N E Sandy Blvd

P 0 13096503 282 9636

SEATTLE. WA 9/109432 Yale Ave N P 0 9275

206 623 2370

SAN JOSE. CA 95112466 Reynolds Corcle

408.289,1117

MOUNTAINDENVER

Arvada C0800014958 Alloson 51 P.0 672

303.4237080SALT LAKE CITY. UT 14108

1233 Wilmington AveP 0 6218

1301 484 1451PHOENIX A215009

2916 West McDowell Rd602 278.1218

SOUTHWEST

LONGVIEW. TX 75601110 Mopoc Rd P 0 7332

214 753 4334OKLAHOMA CITY. OK 73104

3007 N May P 0 60566405947.2013

HOUSTON. TX 772074376 Telephone Rd P 0 26616

713 644 6793

P OOMONS ON MOW

ON ...Winn.MIONSOMMEN

MOO

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PTS ELECTRONICS, INC.

Electronic SeriIc!ng®

Contents14 Practical Tips For Repairing Auto Radios-Both general and

specific suggestions are given to help speed your repairs of thesepopular units-Homer L. Davidson.

20 Service Management Seminar, Part 3-Profit-and-loss statementscan be the tool for spotting weak areas of your business-DickGlass.

24 The Basics Of Industrial Electronics, Part 9-Examples prove thatNAND and NOR gates can be wired to act as NOT gates. Sixdigital troubleshooting questions with answers and two digital ex-periments are presented-J. A. "Sam" Wilson.

32 Servicing Sylvania Color TV, Part 2-Output of one oscillator isdivided to produce both the horizontal and the vertical sweep fre-quencies. Also, operation of the horizontal sweep and high -voltagesections are explained-Gill Grieshaber.

41 Sam Wilson's Technical Notebook-The interesting subjects rangefrom "in situ" tests to humorous stories-J. A. "Sam" Wilson.

About the cover-The montage design that symbolizes auto -soundproducts is by Mary Christoph. Picture of the auto radio is shown bythe courtesy of RCA.

DEPARTMENTS

4 Electronic Scacner5 Symcure6 Reader's Exchange

11 Troubleshooting Tips

49 Test Equipment50 New Products52 The Marketplace52 Advertisers' Index

New Subscription RatesEffective January 1, 1978, subscription rates for ElectronicServicing were increased to $8.00 for one year and $13.00 fortwo years; there is no longer a three-year subscription.Single copy price (for non -subscribers only) was increased to$2.25: back issues are $3.00. Because of a printing error,rate cards in the February issue reflected the lowersubscription prices. Therefore, persons subscribing inMarch at the lower rates will receive their subscriptions atthose rates. Anyone subscribing after March 31, 1978, at thelower rates will have their payment returned.

Second class postage paid at Shawnee Mission, Kansas and additional mailing offices.Published monthly at 9221 Ouivira Road, Overland Perk, Kansas 66212 by Intertec PublishingCorp., 9221 OuivIra Road, Overland Park, Kansas 66212. Send Form 3579 to 9221 Oulvira Road,P.O. Box 12901, Overland Park, Kansas 66212.

©Copyright, 1978, Howard W. Sams & Co., Inc. All rights reserved. Material may not bereproduced or photocopied in any form without written permission of publisher.

March, 1978 1

We want toput our eggsin one basket... YOURS

- eElectron Tubes Inter-national suppliesmillions of tubesworldwide to equipmentand tube manufacturers, distributors and service dealers.The industry knows us well as a full service tube source with amulti -million tube inventory of over 1000 types available for im-mediate delivery at the most competitive prices.

Get to know us. We can help you with just about any replace-ment receiving or industrial tube you're looking for. Contactyour Electron Tubes International EJ Men= tube distributor orcall us toll -free at (800) 645-9512.

111 IIELECTRONICSELECTRON TUBES INTERNATIONAL, INC.380 SMITH STREET FARMINGDALE. NEW YORK 11735 TEL 516-694-7700CABLE LECTROTEL. FDLE TLX 14-4620

For More Details Circle (3) on Reply Card

Next month,

Electronic Servicingbegins a series about the

circuits and servicing of

Sony Betamax videocassette

tape recorders.

Watch for these informative articles.

Electronic Servicing

Editorial. advertising and circulation cor-respondence should be addressed to 9221Ouivira Road. P 0 Box 12901. Overland Park.Kansas 66212 (a suburb of Kansas City.Missouri). (913) 888-4664.

EDITORIAL

RONALD N MERRELL. Director

CARL H BABCOKE. Editor

MICHAEL SCHEIBACH. Managing Editor

DUDLEY ROSE. Art Director

CINDY NELSON. Editorial Assistant

MARY CHRISTOPH. Graphic Designer

EDITORIAL ADVISORY BOARDLES NELSON. Chairman

Howard W Sams & Co.. Indianapolis

JOE A GROVES. Technical ConsultantHoward W Sams & Co_ Indianapolis

CIRCULATION

EVELYN ROGERS. Manager

/10

r

Member. American Business Press

Member. Audit Bureau of Circulations

ADMINISTRATION

GEORGE H SEFEROVICH. President

MIKE KREITER. Publisher

ADVERTISING SALES

Overland Park. Kansas 66212(a suburb of Kansas City. Missouri)

Phone: (913) 888-4664

MARILYN CARROLL, Production

Regional and Advertising Sales Officeswith Advertising Index

ELECTRONIC SERVICING (with which iscombined PF Reporter) is published monthlyby Intertec Publishing Corp . 9221 OuiviraRoad. Overland Park. KS 66212

ELECTRONIC SERVICING is edited for tech-nicians who repair home -entertainment elec-tronic equipment (such as TV. radio. tape.stereo. and record player) and for industrialtechnicians who repair defective production -tine merchandise. test equipment. or in-dustrial controls in factories

Subscription prices to qualified subscribers:1 year-S8.00. 2 years-S13.00, in the USAand its possessions. All other foreigncountries: 1 year-$11.00, 2 years-$19.00.Subscription prices to all others: 1 year-S25.00. 2 years-$50.00. in the USA and itspossessions. All other foreign countries: 1

year-$34.00. 2 years-$68.00. Single copyprice $2.25: back copies $3.00. Adjustmentnecessitated by subscription termination tosingle copy rate. Allow 6-8 weeks delivery forchange of address. Allow 6-8 weeks for newsubscriptions.

INTERTEC PUBLISHING CORP.Subsidiary of HOWARD W SAMS & CO . INC

2 ELECTRONIC SERVICING

fi

4411111111111W

Claudette S. Wiley.Hoironics

NASA; National Aeroilantics and SnAkc \dniiiii.,i1.11 if )11.

Goddard Space I li5110 Center, Green Ii. MU 20771

jl

*.111111.111ampep

Mb'F.Nrt) CONI .RA.1 ,r

ICM IR.

"When the countdown beginsthat's no time for electronic

component failure.We trust GE

replacement semiconductors:'Your reputation is our reputation

Tuba Products Department Owensbol ) KentLcior 42301

Ale

GENERAL (6) ELECTRIC

-

MOEMICalliernews of the industry

Brian J. Marohnic, national service manager for the Zenith Radio Corporation,retired on January 31, 1978, after 44 years with the company. Brian (sometimescalled "Bronc") had been national service manager since 1963. He is succeeded byRichard C. Wilson, former West Coast field engineer, who has been with Zenithfor more than 25 years.

American Telephone And Telegraph (AT&T) has widened the bandwidth of itsaudio microwave and phone lines (that distribute network TV programs over theUnited States) from the former 100 -to -5,000 Hz to the new 40 -to -15,000 Hzbandwidth. For the first time, high-fidelity TV sound is possible. However, beforethis improved frequency response can be heard, new TV receivers must bedesigned with better audio amplifiers and speakers. Therefore, about two years willbe required before any new models can feature hi-fi sound. If stereo TV sound iswanted, AT&T can add an identical second channel.

The FCC has begun a nationwide crackdown on the sale of illegal 23 -channel CBradio transceivers. U.S. marshals and FCC agents seized 350 23 -channel CB radiosfrom a retail store in Alabama last month. In October of 1976, the FCCannounced a ban on the 23 -channel CB radios, to become effective January 1,1978. The radios were banned because they did not meet the new specificationsthat are necessary to minimize interference with TV receivers. (Owners whopurchased 23 -channel radios before that date may continue to use them.) Similarraids are planned for other localities. Persons convicted of these violations mightface a fine and a prison term.

The FCC has banned the manufacture and sale of linear amplifiers (of the kindoften used illegally to increase the power of CB transmitters). According toElectronic News, the agency also decided to require type -acceptance of linearamplifiers for -radio amateur use, so the units could be designed to preventoperation in the 24 -to -35 MHz CB range. The ban will begin 30 days after a noticeis published in the Federal Register.

For many motorists stranded in the February blizzards, CB radio was the onlymethod of communications available for emergency rescue operations. A bulletinfrom the Electromc Industries Association (EIA) credits CB volunteers with savingfour lives in Lowell, Indiana. Numerous state police headquarters and otheremergency officials reported that without the volunteer help of CBers,snowmobilers, and four -wheel -drive enthusiasts, rescue work would have beendelayed and many lives lost. The manager of React International (a nationalvolunteer group with 2,000 local chapters that monitor CB channel 9 offering helpand assistance) also reported a large effort by the Massachusetts React chapters.

Color TV sales to dealers for 1977 were the second highest in history, reaching9,106,826. According to the EIA, color sales to dealers in January of 1978increased 2.3% over January of last year; nowever, B&W receivers declined 12.4%.January sales to dealers of radios with FM increased 33% over January of 1977.while AM radio sales decreased 2%.


Needed: Schematic and parts list for B&K-Precision120 VOM. Will buy, or copy and return. Carl W.Higgins, 2242 South 85th East Avenue, Tulsa, Okla-homa 74129.

Needed: TA -33 or equivalent tri-band antenna.Kenneth Bullard, 107 Fulton Drive, Kings Mountain,North Carolina 28086.

Needed: Schematic and service manual for a CloughBrengle oscillator model OC; also need a 9QP4 picturetube. Will buy tube, and copy or buy schematic.Charles L. Gauket, 14 Bell, Florence, Kentucky 41042.

For Sale: Spectrum analyzer, H/P model 3580A, justcalibrated and in mint condition. Best offer. RonLemke or Joe Flanner II, Flanner & Hafsoos MusicHouse, 2500 North Mayfair Road, Milwaukee, Wiscon-sin 53226, [414] 476-9560.

For Sale: B&K-Precision instruments with cables andmanuals (never used): 1077 Analyst, $375; 415 sweep/marker, $375; 1246 digital/IC color generator, $100;and E200D solid-state RF generator, $125. All pricesFOB. Q. S. Hoshal, 1513 Hillside Drive, Bel Air,Maryland 21014.

For Sale: 1077B Analyst (new), 415 sweep/marker,467 CRT analyzer/restorer (new), and 162 transistortester, all by B&K-Precision, and less than two yearsold. Also, Leader color -bar generator; EICO tubetester model 667; Leader FET-VOM; B&K-Precision501A curve -tracer; Leader 5 -inch scope model LB -501;Sprague capacitor analyzer model TO -6A; about 300TV and radio tubes; and one lot of new TV parts.Milton Obuch, 1308 North 4th, Sayre, Oklahoma73662.

Needed: Old service magazines and pre -1940 publica-tions about all facets of radio. State cash price.Donald Erickson, 6059 Essex, Riverside, California92504.

For Sale: Southwest Technical Products prescaler forany frequency counter, 500 millivolts maximum inputlevel, divides by 10 up to 175 MHz, perfect condition,$30. John Augustine, 530 North 9th, Reading,Pennsylvania 19604.

Needed: Service information for United ScientificLabs, Contact 23, CB radio. Will pay for copying andmailing. Don Gross, Vision Enterprises, CameronMills, New York 14820.

Needed: Schematic for Sencore caddy -bar juniormodel number CG22. Active TV, 14547 South Halsted,Harvey, Illinois 60426.

For Sale: Printed -circuit -board supplies, valued atmore than $40 for $10; high voltage section of a HeathGR270 color TV. $20. and 5 years of Radio Elec-tronics magazines, $4 per year or 60 issues for $15.Douglas Mace, R.D.4, Box 84, Bellefonte, Pennsylvania16823.

continued on page 8

FREEorrir

to,H.t.1978 Catalog _I"cs

Featuring the finestElectronic test equipment

With this catalog you can browse through one of the nation'slargest electronics warehouses. packed floor to ceiling with thefinest test instruments. Everything from probes to dual tracecopes: and everything at sensational savings made possible

only by mail order selling. Volume pricing on orders over $500give you even greater savings. Every item is backed by a big

brand name. Shipment is prompt from stock. always freightprepaid and there never is a handling charge on orders overS200. Write today for the big free catalog of the big brands thatofterc you the big savingc

SAVE STEPS SAVE TIME SAVE MONEYDept. ES -378

NORTH ii\AERICA ELEORCNICS

1468 West 25th Street Cleveland. Ohio 44113

Fa More Details Circle (4) on Reply Card

March, 1978 7

Water permeability

You'll Find a

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NEW IMPROVEDHIGH VOLTAGE

it

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WeatherproofsQuiets, withstands Heat, Cold,Exposure. Ideal for Electricans,Technicians, Mechanics...

It's a space age composition . .. a lightweight,pliable, self -sticking synthetic black rubbermaterial. Posseses excellent adhesion qualitiesand exceptional resistance to the effects ofhigh voltage and ultra -violet light. It maintainsa tight seal under changing weather conditionsand temperatures ranging from -65°F. to 180°F.Indefinitely resilient, it conforms readily toirregular surfaces and will not shrink, crack,sag, or oxidize. Just one ply (approximate thick-ness 1/8") is sufficient to really do the job!

Specs like:(negligible)

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Immediate Delivery From Your Oneida Distributor

0 ONEIDA ELECTRONIC MFG.INC.nada P 0.Box 67/,Baldwin Street Eit.,Meadville,P3 16335Phone (/14)336-2125

winlexchanuecontinued from page 7

Needed: Service or operating manual for Precisepower -lab model 713. Roger Mosley, de YoungMuseum, Golden Gate Park, San Franscisco, Cali-fornia 94118.

Needed: Schematic for Knight solid-state Star RoamerII, five -band receiver. Tiny's Radio & TV, 18606Gable, Detroit, Michigan 48234.

For Sale: Radiola III manual, 26 pages from 5 sources,$5; Rider's Radio Master Index for volumes 1 to 15,$12.50 or volumes 1 to 23, $15; early Rider's volume 1,1919 to 1927. 200 pages, $17.50; Rider's Radio volumes9. 10, 12, 15, 16, 17 and 19, $10 each; also, send fora list of other Riders books. Antique Radio Shop, 3403Broadway, Long Beach, California 90803.

Needed: A power transformer part number 101408 fora Knight scope model KG -630, or the equivalent.William Mayer, 5722 SW 1st Court, Cape Coral,Florida 33904.

For Sale: Sencore SM152 sweep/marker generator,$175; and Sencore TF-1S1 transistor tester, $60. Bothin A-1 condition, with cables and manual. Val Obal,3201 South 73, Omaha, Nebraska 68124.

For Sale: Heathkit scope model 10-4540, completelyassembled, used only a few hours, $145. P. T. Hauser,190 Alexander Avenue, Upper Montclair, New Jersey07043.

For Sale: Bell & Howell (Heathkit) digital multimeter,like new, $25 plus postage. Robert M. Dorman, 1917Ridge Lake Drive, Chesterfield, Missouri 63017.

For Sale or Trade: Bell & Howell radio and TV courseof 10 volumes, scope, TVOM, circuit -design board,plus all parts for the experiments; sell for $275, ortrade for a triggered -sweep scope. Daniel Seidler,5827 South Campbell, Chicago, Illinois 60629.

Needed: Power transformer part number 23213084 forSinger TV model HE -8050. Also, an on/off switchnumber 24056003. Please, state price and condition.Aurie Antilla. 4066 Mount Everest Boulevard, SanDiego, California 92111, ES3-876-R462787.

Needed: Schematic for a H. H. Scott L. K. 72 stereoamplifier kit, 80 watts, around 1962-1963. Will buy, orcopy and return. Anderson Electronics, Box 859,Oakhurst, California 93644.

For Sale or Trade: 25 Radiart car -radio vibrators,assorted; and 12 assorted Delco volume, tone, andswitch controls. Troch's TV, 290 Main. Spotswood,New Jersey 08884.

Needed: TV service equipment: dual -trace scope;transistor curve tracer; scope calibrator; ATC-10color generator; EICO 685 transistor analyzer;B&K-Precision 970 analyst; Sencore YF-33 yoke andflyback checker; and Heath 10-4101 vectorscope.Please advise condition and price. Thomas Walls,6360 Montgomery, Philadelphia, Pennsylvania 19151.

For More Details Circle (6) on Reply Card8 ELECTRONIC SERVICING

Iroubleshooliilen

Pincushion components run hotGTE -Sylvania D19 (Photofact 1269-3)

Several similar models have these defects, whichproduce varied symptoms, such as: no high voltage;no vertical sweep; intermittent height; or the smell ofhot components.

PINCUPHASESH

10330

PINCUI39 Mein10% 2"?

2Yv

On the convergence board, check the pincushion -amplitude control (R848) for burned appearance orerratic operation, and look at the T800 pincushiontransformer for burned windings.

It is not clear which of the two components failsfirst. Current from the cold end of the vertical yokeflows through L807, R848, and one winding of T800.The other winding of T800 has horizontal pulses fromthe flyback. The vertical current permits T800 toload -down the horizontal -sweep circuit near the top

"Of course this will be just an estimate.The actual cost will be more."

and bottom of the picture, thus reducing the widthand pincushioning there. That's normal operation.

Several times, after the two bad components werereplaced, the horizontal pulses at T800 have measuredtoo high (also the HV was excessive). It seems likelythat the abnormal pulse amplitude caused shortedturns in the original T800, and this changed theprimary -to -secondary turns ratio, thus applying anexcessive pulse amplitude to the "pincushion -ampli-tude" control (R848). In turn, R848 operated too hotand failed.

In any event, make certain the high voltage is nohigher than 25KV with a black raster, and thatneither T800 nor R848 operates too hot after they arereplaced.

Sargent's Distributing CompanyBellflower, California

Blackout after warmupRCA KCS169B B&W (Photofact 984-2)

Gradually, the sync weakened; and after 15 to 30minutes of operation, the raster disappeared.

These symptoms seemed to indicate a problem witheither the 8FQ7 oscillator or the 33GY7 horizontal-output tubes. However, replacement of both tubes did

continued on page 12

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March, 1978For Color Brochure Only Circle (7) on Reply Card

11

Finding the right semiconductor replacement is easy with

troubleshoothencontinued from page 11

not change the symptoms.Because the output tube glowed red after the

blackout, I replaced the flyback. That did not helpeither.

SW ONVOLUME

rNTROL

0ASV@

290ma

FEE

RECT

68 Mk 6 9 ,vim+

.350 1WFUSIBLE

1212 1 4 4

27V IN 9 5V IV

Finally, after many other tests, I noticed that theheaters of this hybrid chassis were supplied throughdiode X2, which reduced the heater -string voltage byeliminating the negative peak of the line voltage. I

looked more carefully at the tubes, and realized theirheaters all were too bright. Replacement of theshorted diode cured the twin problems.

Evidently, the overloaded heaters had caused gridleakage (or other defects) from the excessive internalheat, thus affecting the sync clipping and theoperation of the horizontal oscillator.

Robert MarchantManomet, Massachusetts

Black area moved upwardRCA CTC51 /52 (Photofact 1361-2)

A black triangle near the right edge of the screenmoved slowly upward, and the color had foldover atthe same area.

2NO CHROMA

BANDPASS AMP

6GH8A

..T. 01

210VIA

Now, the black triangle might have originated in avideo stage or the power supply, but the effect on the

12ELECTRONIC SERVICING

RCA's all new1978 Replacement Guide!RCA's biggest and most complete Guide, ever. Ourcomprehensive line of replacement transistors, rectifi-ers, thyristors, integrated circuits, and high voltagetriplers has now grown to over 750 SKs that replace143,000 domestic or foreign semiconductors. And it's allunder one cover.It's an encyclopedia of solid state replacements. Thenew Guide includes 387 SKs which have been added tothe line since February 1977. It contains 240 pages thatrepresent thousands of hours of engineering know-how.Everything you need to stay up-to-date. The new Guidecovers consumer, TV, Hi-Fi, CB and industrial applica-tions. And more importantly, they're available from yourRCA SK distributor. And remember, too, that every RCASK is backed up by RCA. They're Top -of-the -Linequality.Ask your RCA Distributor for a copy of the 1978 SKReplacement Guide. Or write, enclosing $1.50, (check ormoney order) to: RCA Distributor and Special PoductsDivision, PO Box 85, Runnemede, NJ 07078.Rcp SK Replacement

Solid State

color indicated a defect in a color stage.This trouble was traced to the V4A second-chroma

stage, where the R22 cathode resistor had beenoverheated.

After the 6GH8 tube and the 390 -ohm cathoderesistor were replaced both symptoms were gone.According to our tube tester, the tube was shorted.

Vidal V. Cantu. Sr.Laredo, Texas

Vertical won't lock and linearity poorMagnavox B&W T960 (Photofact 1406-2)

Over the years, 1 have found a component failurethat happens often and is a bit hard to find.

CT.)VERT VOID

I met)

to lock. Also, the frequency often is half the correctrate, showing two complete pictures with one abovethe other.

In all of these cases, the bad part had been C403,the .0015 capacitor that couples the positive feedbackto the grid of the vertical -oscillator tube.

Eddie C. LaneChampaign, Illinois

Vertical flip or poor lockingPanasonic CT -26 and others (Photofact 1371-1)

Some of these hybrid TV receivers are labeledSinger, or other house brand. They can be recognizedby the 12FQ7 phase splitter in the sync circuit and the25HX5 vertical tube.

Usually, the original complaint is no -picture or noheight. After repairs have eliminated the primarysymptom. they often display poor sync, vertical flipevery 16 seconds, horizontal jitter, or a buzz in the

11 1V sound.There problems usually are caused by an open

electrolytic capacitor on the IF/sync/AGC circu:tboard. There are six or seven of them, all mountednear one end of the board. It's so much trouble toremove and test them all (and sometimes more thanone is bad), that I have started "shotgunning" thecircuit by replacing all of these capacitors. Heatappears to hasten the failures, so I clean out the dustwith a paint brush, and also clean the air -vent holesin the cabinet.

The symptoms range from a complete loss of John Couter, Sr.vertical sweep, to severe non -linearity, and a failure Roanoke, Virgina

k -F -1 17118

vFItt MUTT

1 15 66V

100039

10% II

March, 1978 13

Practical Tipsfor Repairing

Auto Radios By Homer L

Auto-radio/tape-player sales andservice continue to be a boomingmarket. Veteran servicer HomerDavidson gives many helpful tipsfor .finding the source typicaldefects in auto -sound equipment.

Quick Radio RepairsAre Profitable

Whenever a technician knowswhich section or stage the defect isin, he always can save much timeduring repairs of any electronicproduct. With auto -sound equip-ment, this saving of time oftendetermines whether the shop makesa profit or suffers a loss, since thelow original cost limits the maxi-mum amount that can be chargedto the customer.

The practical tips and shortcutsin this article should enable you toidentify more rapidly the areawhere the problem is located.

Comparison MethodsAn excellent first step of efficient

troubleshooting is to make com-parisons of the performances of amalfunctioning item of equipmentand another identical unit that'sworking correctly.

However, in the repairing ofauto -sound equipment, two radiosor two tape players of the samemodel often aren't available fortesting simultaneously. Secondchoice for valuable comparisons isbetween similar models. These canbe very informative, and often tellyou enough.

For some symptoms, radios thathave several functions (such asradio and tape player, or AM radioand FM band) permit comparisonsbetween these functions. Exampleswill be given later.

Other valuable comparisons arethose between the instrument beingtested at the time and the perform-ances of similar radios or tapeplayers that are remembered by the

technician. Experienced techs al-ways know which FM stationsshould be received noise -free at thatlocality. Or, he knows how themusic of his test cassette shouldsound on a typical tape player.

Although these remembered pastperformances can't allow accurateevaluations, they nevertheless serveas important guideposts to thequality of performance that shouldbe obtained. Any significant devi-ation from the average indicates aneed for repairs. In fact, the typeand general location of manydefects often can be identified.

Play The PercentagesSome defects are more likely to

occur than others are. Capacitorsfail more often than resistors. Badsolder joints occur most often wherethe current is highest, or aroundheavy components. Some bad com-ponents can be found by movingthem physically.

Defective components tend to failin patterns. For example, the samecomponent fails in many individualmachines of the same model. Aknowledge of such repetitive orrecurrent failures permits a tech tofind those defective parts in quicktime.

The technique of starting withthe most probable component fail-ures sometimes is called "PlayingThe Percentages."

Go On To The Next LevelIn those cases where the com-

parisons, memory, and probabilityof defects don't locate the problemarea, you should go on to moreaccurate and technical methods.These involve additional test equip-ment, coupled with logical trouble-shooting.

Specific TipsNow that we have covered the

types of repair methods that arerecommended for auto radios and

Davidson

tape players, we will give somespecific examples.

Types Of RadiosAlthough a small percentage of

present-day radios have AM bandonly, FM operation is very popularwith the drivers and passengers. Infact, many listeners tune in FM -stereo programs because of thebetter tone quality and the noise -free reception.

Also, many car radios of todayare combined with Stereo -8 orcassette tape machines (Figure 1).

Naturally, radios with FM -stereoand tape players require moreservice, including the possibility ofseveral problems when repairs areneeded.

The majority of radio -serviceproblems are no reception (radio isdead) and intermittent reception.Of course, noise and audible dis-tortion also are common com-plaints.

Isolating The ProblemFor the first step of troubleshoot-

ing, verify the complaint that'slisted on the service ticket. Then, ifthe radio works at all, quickly testthe operation for yourself.

Dead receiverTotal loss of sound might be

caused by an open fuse, an open orintermittent connection in the "A"power lead, or a defective on/offswitch.

While your ear is near thespeaker, turn on the power switch,listen for a click or a thump, andlook for lighted dial lamps. Anynoise from the speaker proves thevoltage is reaching the outputtransistor.

Remember that the dial lamp insome receivers is controlled by thecar's light switch. If so, a lighteddial lamp is not a reliable symp-tom.



FM IF AM OSC AM -UNING FVI RF F141 TU/IINIGAND OSC

AM IF

MAN UALTUN ING

rA JLTIPLEX

AUDIO

PUSHBU-TONS

VOLLrolECCNTFOL

Arrows point out the p-incipal circuits and mechanisms of a typical auto racio.

VOLUMECONTROL

SPLA-ER

-12

Capacitors, ICs, 3rd powar ransistors are tle audio components most sJscep:ible to failures.

Radioscontinued 'aim ?age 74

Figure 1 Many modern au:c radios also lave a Ste-eo-8 taoe player.

Figure 2 A small ncise generator can locate man,/ defective stages itminimum times.

Intermittent receptionIf the radio has intermittent

volume, use another function todetermine whether both the AMand FM reception are affected, or ifthe radio bands are intermittentand the tape -player volume is not.Use these symptoms to find thebasic circuit that has the intermit-tent. For example, if both AM andFM sounds are intermittent, butthe built-in tape player worksnormally, the problem is in theradio RF or IF sections. If AM,FM, and tape sounds are allintermittent, the defect must be inthe audio or speaker.

Incidentally, the two identicalaudio channels for FM or tapestereo make possible a comparisonof volume, distortion, and gainbetween a bad channel and a goodone.

Simple Signal InjectionA hand-held noise generator (see

Figure 2) can be used for signalinjection in the RF, IF, and audiostages. Touch the probe to the hotend of the volume control to proveif the audio is operating. If noaudio tone can be heard with thecontrol adjusted to maximum, youcan use the probe to inject the toneat each audio stage in turn. A deadstage will be identified when a tonecan be heard with the probe at theoutput of a certain stage, but notone comes through when it is in-jected at the input of the samestage.

Of course, a loud audio tonewhen the probe is applied to thevolume control of a dead radioproves the trouble is in a previousIF or RF stage. The noise -generatorsignal can be injected at the inputand output of those previous stagesto locate the dead one.

Signal InjectionFrom A Generator

Sometimes a noise generator isnot effective in certain stages. Forexample, the high -frequency outputis not always sufficient to supply anRF or mixer stage. Also, good FMlimiting tends to remove the ampli-tude modulation, so the resultsmight not be definite enough forFM IF stages.

For such conditions, a single (but


adjustable) frequency from an RFsignal generator is best for injec-tion. With a generator, the exactAM or FM IF frequency can beused, as needed.

In the same way, an audio signalgenerator can be used effectively tolocalize the stage causing weak ordistorted signals. Connect thegenerator through a small capacitor(perhaps a .01, or a .1 in series with1,000 ohms) to the input andoutput of each audio stage. Keepthe generator output level low, toavoid overload in stages that havehigh gain after them.

For example, an open couplingcapacitor can be found by connect-ing the audio generator capacitorfirst to one end of the suspectedcapacitor and then to the otherend. When the coupling capacitoris good, the same volume should beheard as the audio tone is injectedat either end.

Connect your scope to the speak-er terminals, and watch for anydistortion during these tests ofvarious stages.

Dead StagesA dead stage is much easier to

locate than one that is weak or

POOR RFANTENNA TRANSISTOR

CONNECTIONS

intermittent.The signal -injection method, de-

scribed earlier, is not effective if theoutput audio stage is dead. Forthose conditions, connect an audiogenerator to the volume control andtrace the following stages to findwhere the signal stops.

Experience has shown that mostdead and distorted symptoms in carradios have been caused by shortedor open output transistors. Also,shorted transistors usually ruin thesmall -value collector or emitterresistors. So, look for burned orsplit resistors. Replace them andany that have changed value fromthe overload.

Smaller pre -amp and low-leveltransistors usually can be testedin -circuit with fair accuracy. How-ever, driver transistors and outputtransistors require removal beforeleakage or gain measurements canbe made accurately.

Intermittent OperationIntermittent sound can be caused

by almost any component in a carradio. In addition, poor connectionin a fuse holder or an antenna jackcan be mistaken for an internalradio problem.

OPEN BROKEN- - BYPASS COIL LEADS

Before you pull the radio for thebench, check the antenna andshielded lead wire. While you listento the radio, flex the verticalantenna rod, and notice if thevolume becomes intermittent. Some-times the lead wire breaks at thebottom of the antenna or where itplugs into the radio. Check thosespots first.

Occasionally, water leaks into theshielded cable, causing weak andnoisy reception. In such cases, it'sadvisable to replace the antennaand lead wire.

Other intermittents inside theradio include cracked connectionson the circuit boards, broken coilconnections, and erratic transistors.Many conditions that cause inter-mittent operation can be found byslightly moving the suspected com-ponents. IF transformers and RFcoils should be tested this way.

Intermittent transistors often canbe identified by alternately applyingheat (perhaps from a soldering iron)and canned coolant to each transis-tor.

Volume controls can becomeerratic, causing noise when they areturned and intermittent volume ifthey are stopped at a bad spot of


IFIF TRANSISTOR

Arrows point to the radio RF and IF components that are most like y to cause trouble.

March. 197817

Radioscontinued from page 17

the internal element. Sometimestuner spray applied to the carbonelement will stop the noise tempor-arily. This positively identifies thedefect, but the control should bereplaced to avoid future problems.

Speakers also can become inter-mittent. Substitute a test speakerwhile the radio is still in the car.That test works fine, too, forsuspected bad antennas. Unplugthe car antenna, plug in a replace-ment antenna, and hold it out thecar window while you notice theperformance.

Weak VolumeMany of the components that

cause intermittent volume also cancause weak sound. The symptomsvary according to the extent of thedefect.

Open coupling and emitter -by-pass capacitors can reduce the gaingreatly, without always causingdistortion. Open coupling capacitorsproduce high-pitched sound quality,or no volume at all. Open emittercapacitors often reduce the volume,but the tone quality is okay.

Cracked cores in RF or IF trans-fcrmers reduce the gain seriously,without changing any of the DC -voltage or resistance readings.

Sometimes an output transistorthat's drawing too much current

Figure 3 Many mechanical problems originate in the slip -clutch that dis-connects the manual tuning when a pushbutton is used.

Figure 4 Both mechanical and electronic problems often originate in thepermeability tuning system of car radios.

will reduce the supply voltage to theoscillator. The symptoms can beweak reception of all stations; orthe radio might be weak belowabout 700 KHz and dead abovethat point on the dial.

Check the voltage drop across theemitter or collector-decoupling re-sistor to prove whether or not anRF or IF transistor is conducting.Transistors can feed a weak signalthrough the internal capacitance,even when the transistor is dead orbiased to cutoff.

DistortionA leaky AM -detector diode can

cause distortion of the AM soundonly. Failure of the AM AGC mightoverload the last IF transistor andproduce distortion, along with ex-cessive AM volume. Unbalanced ormistuned FM discriminators typi-cally generate much distortion.

However, except for these indi-vidual sources of distortion, mostdistortion originates in the audiostages. This diagnosis is proved ifboth AM and FM sounds have thesame amount of distortion.

When distortion is combinedwith weak sound, one or more leakytransistors should be suspected.

Open or shorted bias diodes(those between the bases of theoutput transistors) cause a moderateamount of distortion.

MotorboatingUsually, motorboating (put -put

noises) originates in leaky outputtransistors or open A -supply de -coupling capacitors. In some cir-cuits, leaky output transistors mere-ly drop the volume and adddistortion. However, when theemitter voltage furnishes bias to aprevious stage, leakage in an outputtransistor can cause motorboating.

Oscillation and motorboating canoccur because of an open bypasscapacitor in the IF circuit. Brokengrounds between the circuit boardand the metal cabinet might causethe same symptoms.

Mechanical ProblemsMost mechanical problems of

auto -radio receivers are related tothe tuning and dial -drive mecha-nism (see Figure 3). This clutchmechanism usually disconnects the


manual -tuning knob when the push-buttons are used. Part of the clutchis a flat washer with an attachedrubber washer. If the rubber be-comes loose from the metal washer,the clutch slips, and the manualtuning can't be operated. The partsusually can be fastened together byrubber cement (or phono-grip, forstubborn cases).

When the iron -core tuning as-sembly (Figure 4) can't be moved,one of the cores might be "frozen"inside the coil form. Or, if the radiohas been in an accident, one ormore of these cores could have beenbroken, jamming the mechanism.

Stringing of the dial cable can bea tricky job, especially if the cablebroke before you could examine theway it goes around the shafts andpulleys. I recommend that you referto the Photofact "AR" auto -radioseries for dial -stringing drawings.

CommentsAuto radios contain more dust

and be more compact than com-parable table models. However,

are serviced by the samemethods.

When you replace any powertransistors, remember to apply sili-cone grease to the transistor and tothe heat sink (or chassis), andreinstall the mica insulator betweenthe transistor and the heat sink.However, don't install more thanone; this mistake allows a transistorto run excessively warm.

If you specialize is just onebrand, it save time to make up acable harness to connect the radiosto the power source and the testspeaker. Makeshift connections cancause intermittents, or they canblow output transistors. Paint theplug of each cable harness a

distinctive color to remind you toremove the harness before returningthe radio to the customer.

Your equipment should includean RF generator for those align-ment jobs where an unskilled techor car mechanic has turned all ofthe adjustments. Also, for bestsensitivity, you should tune in a

station around 1400 KHz (after theradio is in the car, with its ownantenna) and adjust the antenna-

trimmer capacitor for maximumvolume. 0

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For More Details Circle (8) on Reply CardMarch, 1978 19

Service ManagementSeminar, Part 3By Dick Glass, CET

Profit -and -loss statements are valuable for more than helping compute theincome tax. Use them as a management tool to spot unprofitable areas of youroperation.

What's The Score?Can you imagine a football game

between Notre Dame and Texas,with no one totaling the score? Theplayers continue to run, pass,block, punt, and make touchdownsin brilliant displays of power andskill, while the fans cheer wildly foreach successful play of their team.

However, many mistakes aremade, because there's no score-board or time clock. A coach mighttake unneccessary risks, not know-ing his team is safely ahead. Or, heomits a play that could bring a fasttouchdown (but would not be goodlong-term strategy), because hedoesn't know his team is behindand the clock is running out.

After a time, the enthusiasm ofboth fans and players begins tofalter. Much of the excitement isgone when neither team wins.

The moral is obvious: games ofsport must have scoreboards andtime clocks. Your business, too,needs (for proper planning andgood morale) a scoreboard called a"profit -and -loss" statement, cover-ing a definite period of time. It's

not enough to "play the gamehard" by repairing all the machinesyou possibly can. You must know ifyou're winning or losing the eco-nomic "game."

A few dollars in your pocket afteryou have paid all of the billsdoesn't prove your business isprofitable. Instead, you must com-pare total income with total ex-penses.

P&Ls Are Easy To UnderstandIf studying your profit -and -loss

(P&L) statements required two orthree hours of your time each week,or if you were forced to do complexmathematical computations, per-haps you would be justified forgiving the work to your accountant.Fortunately, that isn't the case.P&L statements are easy to under-stand. After you become skilled atinterpretation, you probably willspend only minutes a month inchecking your "score."

Many shop owners feel uncom-fortable with a P&L because theydon't understand all the advantages

DICK'S TV SHOPProfit and Loss Statement

1-1-77 to 12-31-77

INCOME

Total labor andparts sales $100,000

EXPENSES

Wages, parts costs,and overhead expenses $90,000

NET PROFIT $ 10,000

Figure 1 Although very short, this is acomplete P&L. It shows total income,total expenses, and net profit.

and uses. Perhaps only one issupplied to them per year. Oftenit's used solely as a step in thecalculation of taxes. Unfortunately,this neglects some valuable appli-cations of P&Ls.

Instead, a P&L statement shouldbe prepared each month (each weekfor large operations), and used firstas a management tool to monitoryour business constantly.


What Can I Learn From A P&LA P&L statement shows you

these three basic things: The amount of money you re-ceived (total sales). The amount of money you spent(total expenses). How much money you have left(total profit).

Figure 1 shows a condensedprofit -and -loss statement. Althoughit might appear to be too simple, itis complete. It probably doesn'tprovide as much information as youneed, but it's far better thanevaluating your profit or loss by thethickness of your wallet.

Balance sheetsAt this point, perhaps you're

wondering about balance sheets,and whether or not they accomplishessentially the same things as doP&Ls. Balance sheets show whatyou owe and what you own at theend of an accounting period. Theyare important in their own right,and we will explain them thorough-ly next month. For now, it's enoughto know that balance sheets andP&Ls work together.

Expanding the P&LIn addition to the three items

mentioned above, other helpfulinformation which can be obtainedfrom P&Ls includes:

1. A comparison of your presentstatistics with last month or lastyear, to prove whether you aredoing better or worse.

2. You can compare your ex-penses with industry averages, todetermine if improvements areneeded in any certain areas.

3. Your gross profit can beshown (gross profit is found bysubtracting "direct labor" and "di-rect parts costs" from income).

4. Overhead expenses can belisted individually, and totaled, thushelping you to determine efficiency.

5. It can show the actual costs,allowing you to bill labor and partscharges more accurately.

Tips for P&LsEven if you have a one-man

operation, you should have a P&L

DICK'S TV SHOPProfit and Loss Statement

1-1-77 to 12-31-77

INCOME

Labor incomeParts income

Total sales

$50,000$50,000

COST OF SALES

Labor sales $50,000Direct wages $25,000

$100,000

Gross labor prof t $25,000

Parts salesParts costs

$50,000$25,000

Gross parts prof t $25,000

TOTAL GROSS PROFIT $50,000

OVERHEAD EXPENSES (general and administrative expenses)

AccountingClerical and administrative

salariesRentTruck expensesUtilities

$ 2,000

$20,000$ 6,000$10,000$ 2,000

411.TOTAL OVERHEAD

EXPENSES $40,006

NET PROFIT $ 10,000

.1111=11110

Figure 2 Income from all basic sources should be listed, along with theassociated expenses, and the items of overhead should be givenseparately. Showing gross profit from each source of income allows youto judge the relative profitability. What's more, you can spot trends bycomparing the gross profits of successive P&Ls.

statement each month and annu- remaining after you subtract fromally. the total income all the direct

An inventory is not necessary forcosts (such as wages for your techs,each monthly P&L. One inventory and the money paid for theper year should be sufficient. comporents). Net profit is calm -

Small business should not handle lated by subtracting the overhead"parts inventory" and "owner's (general and administrative) ex -wages" by the conventional method. penses from the gross profit.Later, we'll tell you why and how. Figure 2 shows another P&L for

The P&L is not an end in itself, Dick's TV, with figures for thebut is merely one tool to help you gross profit included. This P&Lanswer your financial questions. contain; the same information as

the less complicated one of FigureGross profit 1; however, it shows the individual

The term "gross profit" probably items of expense and the compLta-is a leading cause of confusion tion of gross profit. Perhaps yourabout P&L statements. yearly P&L appears to be much

Perhaps gross profit would be more extensive, yet it contains themore understandable if we thought same basic elements as the one ofof it as being an "intermediate Figure 2.frequency" of accounting. Although The greatest value of the Figureit's important, gross profit is not 2 P&L is that it shows how muchthe .final figure we're after. you are spending on the three

Gross profit is the "paper" profit continued on page 22

March, 1978 21

Dick's TV ShopP'ofit and Loss Statement

1-1-77 to 12-31-77

INCOME

Labor income $50,000 50%Parts sales $50,000 50%

Total sales $100,000 100%

COST 0= SALES

Labor sales $50,000Direct wages $25,000 25%

Gross labor profit $25,000 25%

Parts sales $50,000Parts costs $25,000 25%

Gross parts profit $25,000 25%

Total Labor andParts costs $50,000 50%

TOTAL GROSS PROFIT $50,000 50%

OVERHEAD EXPENSES

Accounting $ 2,000 2%Clerical & Administrative

salaties $20,000 20%Rent $ 6,000 6%Truck expenses $10,000 10%Utilities $ 2,000 2%

TOTAL OVERHEAD EXPENSES $40,000 40%

NET PROFIT (before taxes) $10,000 10%

Figure 3 Adding percentages to P&Ls allows you to compare those of differentmonths without confusion.

Dick's TV SHOPProfit and Loss Statement

Period ending June 30, 1978

INCOME June '78 Year to date Last year

Labor sales $ 6.000 55% $30,000 55% $ 50,000 50%Parts sales $ 5.000 45% $25,000 45% S 50,000 50%

Total sales $11,000 100% $55,000 100% $100,000 100%

COST OF SALES

Labor sales $6,000 55% 55% 50%Direct labor $2,500 (42%)' 23% $14,000 25 % $ 25,000 25

Gross labor profit $ 3,500 32% $16,000 29% S 25,000 25%

Parts sales $5,000 45% 45% 50%Parts costs $7.,300 (60%)** 27% $15,000 27% S 25,000 25%

Gross parts profit $ 2,000 18% $10,000 18% 5 25,000 25%

Total Labor ancParts costs $ 5,500 50% $29,000 53% 50,000 50%

TOTAL GROSS PROFIT $ 5,500 50% $26,000 47% $ 50,000 50%

OVERHEAD EXFENSES

Accounting $ 167 1.5% 1,000 1.8% $ 2,000 2%Salaries -Clerical & Admin. $1,656 15% $10,000 18% $20,000 20%Rent $1,000 9% $ 5,000 9% $ 6,000 6%Truck expense $ 950 8% $ 4,200 7.6% $10,000 10%Utilities $ 200 1.8% $ 1,300 2.4% $ 2,000 2%

TOTAL OVERHEADEXPENSES $3,933 36% $21,000 39% $40,000 40%

NET PROFIT (before taxes) $1,517 13.8% $ 4,500 8.1% $10,000 10%

Figure 4 The recommended P&L combines all o: the assent al data and thepercentage figures of several P&Ls.

Service Managementcontinued from page 21

largest expense categories: wages;parts or components; and overhead.Efficient operation demands thatyou keep these in balance for thetype of store you have.

Notice that the direct wage costis 50% of the total labor produced.Usually, in this business, 50% wagecosts is too high. The owner shouldincrease the labor income or reducethe wage costs. The parts costs are50% of the parts sales. This isabout right for shops not doingmuch warranty work. Shops havinga high rate of warranty repairsmight only realize 20% to 30% ofparts profits. Lastly, we see that theoverhead expenses are 40% of totalsales. Because the boss (who's not atechnician) has included his ownsalary in the "clerical and adminis-trative salaries" section of overheadexpense, the 40% overhead figureprobably is normal for this shop.

PercentagesWhile the Figure 2 P&L is quite

informative, it lacks one thing:percentages. Otherwise, when youwant to compare the figures foreach month and year, you will belost in a maze of figures. Usingpercentages provides a commondenominator that makes compar-isons easy and fast. Figure 3 is thesame P&L, but with percentagesadded.

There is no limit on the timeperiod of a P&L. It can be daily,weekly, monthly, quarterly, yearly,or whatever is needed.

Exceptions ForService Businesses

Two important differences inaccounting methods are necessaryfor small service businesses: themethod of handling parts costs andinventory; and the owner's salary.

InventoryI advise that a parts inventory be

taken only once per year. Owners ofsmall service shops ordinarily are soinvolved in the details of thebusiness that they are aware ofinventory changes at all times. Also,the proliferation of small partsmakes an inventory a difficultand expensive task. Of course, amonthly inventory is desirable, butthe benefits are less than the effort


required. And the year-end inven-tory eventually will provide theadjustment.

Here is an example of a year-endparts inventory adjustment:

Parts inventory value1-1-77 $6,000

Parts purchases 1-1-77 to12-31-77 $60,000

Total $66,000Less inventory 12-31-77 $16,000Actual parts cost for

12 months $50,000

Owner's salaryIf the owner does no work of any

kind (neither technical nor manage-ment), his salary must come fromthe net profits of the business.Therefore, a non -working owner'ssalary should not be included in thesingle -proprietorship or partnershipP&L. It is advisable to have anotation of the "Owner's DrawingAccount" added at the bottom ofthe P&L to show the amount theowner has withdrawn during theaccounting period. (Incidentally, anon -working owner will pay taxesonly on the net profit shown by theyear-end P&L, regardless of theamount he "draws.")

However, if the owner performstechnical or management functions,his salary properly belongs on theP&L under the correct expensecategory.

For example, if you as the ownerspend 75% of your time working asa technician and the other 25% inmanaging the business, you shouldlist 75% of your salary as "DirectWage Cost," and the other 25%under the "Clerical And Adminis-trative Salaries."

ComparisonsNow that gross profit and percen-

tages have been included, one morestep is needed: comparison of thelatest P&L with the previous one.Although there are many possiblecomparisons, the method I like isshown in Figure 4, which containsall the data listed before.

Analysis of the Figure 4 P&L canspot trends and identify any unusu-al changes before they becomemore dangerous. Notice that the netprofit for the first six months isdown by 19%. It's likely a problemis indicated, but the analysis to

determine the source of the lossshould be continued.

The overhead percentage is 39%,which is down slightly from lastyear, despite the big rent increase;and the gross labor profit is higher.However, the gross parts profitdropped from 25% to 18%. Evi-dently, the lower parts sales (50%went down to 45%) and the risingparts costs (from 25% to 27%)combined to make the parts salesless profitable.

Also, notice the two percentagesmarked * and *4'. The first is theJune percentage of labor costs tolabor sales, which has decreasedfrom 50% last year down to 42%.The other is the June percentage ofparts costs to parts sales, and itincreased from last year's 50% upto 60%. Some shop owners aremore concerned about those twopercentages than about any others.Certainly, they are very important.

Not all the percentages discussedwere listed in Figure 4, but theywere calculated from the figuresgiven there.

In the example, both the totalparts sales and the profitability ofthose sales are exposed as theproblem that needs to be solvedfirst.

The ability to pinpoint indi-vidual increases or decreases is thegreat value of the gross -profitlistings, particularly when there areseveral entries.

CommentsYour P&Ls undoubtedly have

other income categories (perhaps"merchandise sales," rentals, orothers). Also, under General andAdministrative I have shown only afew items instead of the long listmost P&Ls have. Later in thisseries, we will return to Profit -And -Loss statements and explain how tosplit your P&L, separating theservice and sales departments. Also,we will clear up that old nemesiscalled depreciation.

However, if you now are com-fortable with P&Ls and understandhow to use them, it's likely youwon't have trouble with morecomplicated ones.

Use these suggestions about P&Lsto help make profitable decisionsfor your business operation.

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For More Details Circle (9) on Reply CardMarch, 1978 23

The Basics ofIndustrialElectronics, Part 9

By J. A. "Sam" Wilson, CET

NOR gates, EXCLUSIVEOR gates, six trouble-shooting questions, andtwo digital experimentsare covered this month.Also, details are givenabout using NAND andNOR gates to produceNOT gates.

fa'

NOR GateWith NOR gates (Figure 1), the

only way of obtaining a logic 1

output is to have logic 0 at bothinputs. All other combinations ofinputs produce a logic 0 at theoutput. The NOR formula is de-rived from: NOT A OR B EQUALSL.

NOR gate symbols are the sameas those for OR gates, except for anindication that the output is in-verted. In the MIL symbol, thesmall circle at the output showsinversion.

This is an important point,because it hints that a NOR gatecan be constructed from an ORgate followed by an inverter (NOTgate).

In the basic industrial circuit, thenormally -closed relay contact isenergized (logic 1 at the load) onlywhen both switches are open (logic0). When either or both switchesare closed, the relay opens thecontact, producing a logic 0 at theload. This is in agreement with thetruth table.

The math formula is read: NOTA OR B EQUALS L. The overbarmust be across both the A and B,or the equation is written incor-rectly.

Changing A NAND To A NOTIn the February article, I said

that any of the basic logic gatescould be constructed, if a sufficientnumber of NANDs (or NORs) isused. In other words, specificwirings of the NAND gates canproduce any of the basic gates thatwe have described so far. The sameis true of NOR gates.

It's easy to wire a NAND gate soit performs as a NOT (inverter), asshown in Figure 2. The two inputsare connected together; therefore,both inputs always have the samelogic level. A conventional truthtable is used, except the twoconditions when the inputs havedifferent logic levels are not pos-sible. In Figure 2, these entries areremoved from the truth table,leaving only the one with bothinputs at logic level 0 (producing ahigh output) and the other withboth inputs at logic level 1 (for alogic 0 output). Whenever theoutput always is reversed from the


NOR TRUTH TABLE

1

0

NOT ALLOWED BY

PARALLELED INPUTS

A"NOR"GATE CANBE AN INVERTER

input, the circuit is an inverter (or aNOT gate).

Changing A NOR To A NOTA NOR gate also can be wired to

operate as an inverter. Figure 3shows the two entries of the truth

table that are impossible when thetwo inputs are connected together.The only valid inputs are logiclevels 0 and 0. which produce alevel 1 output, and logic levels 1

and 1, Producing a logic level 0output. These characteristics fulfill

Figure 1 These are the four basiccharacteristics of NOR gates.

A

A

SYMBOLS

L MIL

1 NEMA

L

L ANS;

A B L[NOT A OR B EQUALS 1]

MATH SYMBOL

A B

0

0

0

0

0

0

0

TRUTH TABLE

B

BASIC CIRCUIT

"NOR" WIRING

A

A B

0 0

Figure 3 Connecting both NORgate inputs together also elimi-nates half of the truth table,leaving only the function of aNOT gate (inverter).

the requirements for a NOT gate(inverter).

These last two illustrations provethat NOT gates can be constructedby connecting together the inputs ofeither NAND or NOR gates.


Figure 2 Connecting both inputsof a NAND gate together elimi-nates half of the truth table,allowing it to function only as aNOT gate.

'NAND" GATE

A

NAND TRUTHTABLE

NOT ALLOWED BYPARALLELED INPUTS

A"NAND"GATE CANBE AN INVERTER

p+v

TROUBLESHOOTING QUESTION #1:

TO LIGHT THE LED, SHOULD THESWITCH BE AT "A" OR "B" POSITION%

Figure 4

March, 1978 25

Industrialcontinued from page 25

TroubleshootingQuestion #1

Figure 4 asks a questionabout a series of NAND gatesthat are connected as NOTs.What is your answer?


Answer the troubleshootingquestion of Figure 5, concern-ing two NOR gates connectedas NOTs that feed the twoinputs of another NOR gate.

Exclusive OR GateThe symbols, truth table, basic

circuit, and math symbols for anEXCLUSIVE OR gate are shown inFigure 6.

During a previous discussion ofINCLUSIVE OR gates, we men-tioned the two different meaningsof the English word "or." Whensomeone says, "John or Mary maygo to the store," it could mean,"John or Mary or both may go tothe store." This is the inclusiveform. On the other hand, the intentmight be to say, "John or Mary,but not both, may go to the store."This is the exclusive form of "or."

The OR gate discussed in theJanuary issue was the inclusive type

where either or both of the inputshaving a logic 1 produces an outputof logic 1.

From the truth table in Figure 6,we learn that a logic 1 at either(but not both) input produces alogic 1 at the output. Another wayof defining an EXCLUSIVE ORgate is that the inputs must be atopposite levels to obtain a logic 1output. Notice that a plus sign isused both in the NEMA symboland the first formula. In logicsymbols, the plus sign indicatesOR.

The basic industrial circuit needssome explanation. Two relays areprovided, each with one normally -open and one normally -closed set ofcontacts. The normally -open con-tact of M is in series with thenormally -closed N contact. Also thenormally -closed contact of M is inseries with the normally -open N

contact.When neither relay is energized,

no path exists through either pairof contacts (one normally -open isin each path). When both areenergized, all of the contacts re-verse, but still there is no paththrough the series contacts. Theonly way to light the lamp (logic 1)is to energize relay coil M or N, butnot both.

Three-way switchLet's analyze the operation of the

so-called three-way lamp circuit ofFigure 7A. It's used often tooperate a hall lamp from the top orbottom of the stairs, or to control a

"INCLUSIVE OR" GATES

TROUBLESHOOTING QUESTION 02:

WHAT STATE SHOULD THE PROBE INDICATE?

garage light from the house or thegarage.

With the light switches flipped asshown, the circuit is completed, andthe lamp will light. Also, if bothswitches are flipped to the oppositepositions, the circuit again hascontinuity (although through a dif-ferent path) and the lamp isenergized.

However, if just one of theswitches is flipped, the powersource and the lamp are connectedto different wires. Therefore, thelamp does not light.

The logic of the circuit can beunderstood more easily, if the

BASIC CIRCUIT

OE

SYMBOLS

A B

0

0

0

0

0

0

TRUTH TABLE

L MIL

L NEMA

L ANSI

A B

A B+AB-LA HIGH AT EITHER INPUT - BUT NOTBOTH - PRODUCES AN OUTPUT HIGHI

MATH SYMBOLS

Figure 5 Figure 6 Here are the basic character-istics of EXCLUSIVE OR gates.


circuit is redrawn (Figure 7B) inindustrial style similar to the basiccircuit of Figure 6. The resultsagree with the truth table of Figure6.


In Figure 8, given the Binput level and the outputlevel of the EXCLUSIVE ORgate, what must be the logiclevel at the A input?

Combinational LogicMany logic circuits are made by

combining gates. These are calledcombined -logic gates or combina-tional -logic gates. One example isshown in Figure 9. The two inputsof a NOR gate are tied together,making it function as a NOT gate,and it is located between the Ainput and one input of an OR gate.The B input goes direct to the ORgate.

It's important that you determinewhat the output level should be, soyou can know if it is operatingproperly or not.

There are several ways of deter-mining the output logic level (one isby Boolean algebra, but it will notbe explained now). Perhaps theeasiest method is to draw up atruth table (see Figure 9). Write inall combinations of logic levels forthe two inputs.

We know that a NOT gateinverts the state, so we can fill inthe NOT A column, as shown inFigure 10. The original A column isnot used anymore, because theNOT A and the B logic levels arethe input of the OR gate. Next,knowing that the only way to obtainlogic level 0 at the output is toapply level 0 to both inputs, we cancomplete the truth table (Figure11). The last step is to ignore thecolumn, and to use the A and Blogic levels plus the output level.

Notice that the inputs and out-puts were taken a step at a timestarting with the NOR which is

wired as a NOT, continuing on tothe two inputs of the OR gate


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(allowing us to know the output,and finishing by going back to theoriginal A and B inputs.)


Figure 12 shows the logiccircuit of Figure 9, but bothinputs are supplied with logiclevel 0. What level should theprobe indicate at the output?


In the circuit with threeNAND gates of Figure 13,what should be written in theblank spaces of the truthtable?

Experiment #1This experiment is in two parts.

The circuit of Figure 14 shows a7400 -series IC containing fourNAND gates that have beer wiredto make them perform as NOT

gates. First, use your knowledge ofdigital circuits, by completing thetruth table at the left, both for aninput of logic 0 and for logic 1.

Second, wire the circuit as shown.Apply a ground (logic 0) to input Aand use a logic probe to test eachof the four points, writing down thelogic states. Repeat the test withthe A input connected to +5 volts(logic 1), and write down the otherfour logic levels, as measured bythe probe, in the spaces of thetruth table at the right.

Of course, the experimental re-sults should be identical with thepredicted performance.

AC ,=POWER

HOUSE3 -WIRE CABLE

GARAGE

0LAMP

"EXCLUSIVE OR "3 -WAY AC SW TCH 7A

120 V RMS

M N LAMP

M

A

B

N

RELAYS00

7B

Figure 7 This "three-way" lamp wiring (A) has been used gate. (B) Drawn in industrial style, the circuit is almostfor years. It is a practical example of an EXCLUSIVE OR identical to :hat in Figure 6.

INDICATESLOGIC LEVEL 1

TROUBLE SHOOTING QUESTION #3:

FOR PROPER "EXCLUS IVE OR" OPERATION,WHAT LOGIC LEVEL MUST BE AT "A" INPUT?

Figure 8

A

B

CIRCUIT INPUTS

1A

-A

-B L

0 ? 0 ?0 ? 1 ?1 ? 0 ?1 ? 1 ?

INCOMPLETE TRUTH TABLE

COMBINATIONAL LOGIC

Figure 9 Logic circuits composed of two or more logic gatesare called "combination logic." A NOR gate is wired as aNOT, and it feeds one input of an OR gate. From thisinformation, comp ete the truth table.



When you have completedthe truth tables in Figure 14(and both are the same), haveyou completely checked all ofthe NAND gates?

Experiment #2Construct the circuit of Figure 9.

Using a logic probe, measure theoutput when the inputs have thelogic levels shown there. (Obtain alogic 1 by connecting the input to+5 volts of the power supply.Simulate a logic 0 by connectingthe gate to common of the powersupply. Complete the truth table,trying each combination of inputsseparately. The finished truth tableshould be identical to the one inFigure 11.

Answers To TheTroubleshooting Questions

Answer #1. The switch of Figure 4must be in the "B" position toproduce a logic 1 at testpoint 4,thus lighting the LED. The NANDsare wired as NOTs, so a logic 0 atpoint 1 produces a logic 1 at point

2, a logic 0 at point 3, and finally alogic 1 at point 4 for the LED.

Answer #2. The probe of Figure 5should indicate a logic level 0. NORgates #1 and #2 are wired as NOTs,which places a logic 0 at "A" and alogic 1 at "B" of NOR gate #3.With inputs of 0 and 1, the outputmust be logic 0, which can beconfirmed by the truth table ofFigure 1.

Answer #3. The logic level at input"A" in Figure 8 must be 0, if thegate is operating properly. The out-put is level 1, and the inputs of anEXCLUSIVE OR gate must beopposite to obtain that result. In-put "B" has logic 1; therefore,input "A" must be logic 0.

Answer #4. In Figure 12, the logicprobe should show a logic 1 output.The NOR gate has been wired as aNOT, making the inputs of the ORgate a logic 1 and a logic 0. Thiscalls for a logic 1 output level,which can be verified by the truthtable of Figure 11.

Answer #5. The completed truthtable of Figure 13 is shown inFigure 15. That answers the ques-tion, but there's more. Eliminatethe NOT A and NOT B columns,and the truth table that remains


0

TROUBLESHOOTING QUESTION 04:

WITH LOWS AT BOTH INPUTS, WHAT WILLTHE PROBE INDICATE AT THE OUTPUT?

Figure 12

Figure 13

"OR" GATE INPUTS

Ax ,i 'B L

0 1 0 ?

1 1 ?

1 0 0 ?

1 0 1 ?

Figure 10 The NOT A columncan be filled in easily, sincethe output of an inverter al-ways is opposite to the input.As shown, this identifies thetwo inputs to the OR gate(NOT A and B inputs). Fromthe information complete theoutput logic states.

A A BLo

0

1

1

X

0

o

1

0

1

'

-

0

1

Figure 11 After the OR outputis determined, the NOT Acolumn is not needed. Use theA and B columns of the truthtable as the inputs of thecombinational logic system.

COMBINATIONAL LOGIC

TRLTH TABLE

A BA BL0 0

0 1

1 0

1 1

TROUBLESHOOTING QUESTION #5:

WITH THESE INPUTS, WHAT LOG IC STATES SHOULDBE PRESENT AT THE OTHER THREE POINTS?

March, 1978 29


(Figure 16) is for an INCLUSIVEOR gate. An OR has been con-structed from three NANDs! Otherexamples of gates made fromcombinations of other gates will begiven next month.

Figure 14 Calculate the truthtable at the left. Then, con-struct the experimental circuitand use a logic probe to deter-mine the logic states at eachpoint, filling in the truth tableat the right. If the four NANDgates are not defective, thetwo truth tables should beidentical.

Answer #6. No, you have notcompletely checked all of theNAND gates. You have provedcorrect operation when both gatesare switched together, but not withinputs of opposite logic levels.

However, it's likely that NANDswhich pass this test actually areokay. Quick tests have value, butkeep in mind that additional testingmight be required (for example, todetermine the propagation delay).

INPUT

TOP NUMB/RING

_LE

_LE

C

[N SERIES]

7400 IC

1

+5 V

OUTPUT

WIRING FOR THE EXPERIMENT

EXPERIMENT411:

A B C D E

0 __1

THESE "NAND" GATES ARE WIRED AS"NOT" GATES. USE YOUR DIGITALKNOWLEDGE TO WRITE N THE CORRECTSTATES FCR BOTH POSSIBLE INPUTS.

A B C D E

0 - - - -1 _ _ _ _

TEST THE IC CIRCUIT YOU HAVE WIRED,AND RECORD THE RESULTS IN THISTRUTH TABLE. CONNECT "A" TO +5VOLTS FOR A LOGIC 1, OR TO GROUNDFOR A LOGIC 0.

TROUBLESHOOTING QUESTION .6:HAVE THESE TESTS COMPLETELY CHECKED THE NAND GATES?

Figure 15 This is the truth table ofFigure 13, after it is completed.

Figure 16 (far right) After the NOT Aand NOT B columns of Figure 15 havebeen eliminated, the truth table thatremains is the one for an INCLUSIVEOR gate. Therefore, three NAND gateshave been wired to produce anINCLUSIVE OR gate.

A B A lii L.

0 0 1 1 0

0 1 1 0 1

1 0 0 1 1

1 1 0 0 _ 1

TRUTH TABLE FOR THE COMBINATIONALLOGIC OF FIGURE 13

A B L

0

0

0

0

0

TRUTH TABLE FOR AN"INCLUSIVE OR" GATE

LCOMPARE WITH FIGURE 15


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March, 1978 31

ServicingSylvania ColorTV,Part 2 By Gill Grieshaber, CET

The E44 chassis Sylvania does not have a vertical oscillator, and the horizontaloscillator operates at 31,468 Hz. A countdown digital circuit in an IC developsboth vertical and horizontal frequencies. Also explained are the horizontalsweep/HV circuits and the side pincushion correction.

Horizontal -Sweep SystemHorizontal -sweep stages of the

Sylvania E44 chassis before thehorizontal driver are quite unique,and the following stages are moreconventional. Two ICs and onedriver power transistor are the onlyactive solid-state horizontal -sweepdevices on the 02-41656-1 deflectionmodule, which is at your right whenyou face the rear of the chassis(Figure 1).

IC400 is a 16 -pin IC thatperforms the functions of noiseinverter, video amplifier, IF AGC,sync separator, sawtooth source forthe phase detector, and 31,468 -Hzoscillator. (IC400 is shown in thepicture of Figure 2.)

The other IC (14 -pin IC300)accepts the 31,468 -Hz signal fromIC400 and divides by two toproduce the horizontal frequency.Another divider chain in IC300supplies the vertical frequency.

Perhaps you wonder why such aroundabout method is used toobtain the horizontal frequency.The answer involves an understand-ing of composite video and inter-laced scanning. If the horizontalfrequency of 15,734 Hz (for color -

casts) could be divided by 262.5(the number of horizontal lines inone vertical field), this would pro-duce the correct 59.94 -Hz verti-cal frequency. However, dividerscan't divide by fractional ratios.

Therefore, the oscillator works attwice the horizontal frequency(31,468 Hz), and the desired 59.94 -

Hz vertical frequency is obtainedafter a division by 525.

Perfect locking?Because both sweep frequencies

are obtained by dividers from justone oscillator, it seems reasonableto expect perfect horizontal andvertical locking. (After all, that isthe method used at the TV stationsto generate the sync pulses.) How-ever, this is only partially true.After the oscillator is locked to thestation sync, the sweep _frequencieswill be correct. But, remember thatthe sweeps must start and stop instep with the TV picture. Ofcourse, normal locking of the31,468 -Hz oscillator, synchronizesthe horizontal sweep with thepicture. However, the phase of thevertical -sweep frequency must bevaried by the IC circuitry to insureperfect vertical synchronism.

Because IC300 is a "proprietary"IC, no one outside of the OEMmanufacturer seems to know exactlyhow the system works. We are toldthat IC300 contains logic circuitrywhich examines the sync anddecides whether or not it is goodquality NTSC sync. Then the logicswitches to one of two possiblemethods of locking the verticalsweep to the station signal.

Symptoms and testsIn an effort to understand the

sweep dividers, we collected visualsymptoms, analyzed waveforms, andperformed some experiments. Butwithout total success.

When the tuner is changed froma channel without a signal to anormal TV carrier, usually thevertical -blanking bar is visible nearthe top of the picture. Then, with amovement too fast for the eye tofollow, the picture speeds intoperfect vertical lock.

While attempting to determinethe function of the two kinds ofsync that are applied to the dividersin IC300, I bypassed the compositesync at pin 4 with a 0.22 microfaradcapacitor. This nearly eliminatedthe sync, leaving only a smallamplitude of integrated verticalsync. No large change of thevertical locking was noticed, but asmall amount of vertical shimmycould be seen during some scenes.

However, when the integratedvertical sync at IC300 pin 14 wasbypassed in the same way, thepicture rolled upward at moderatespeed after a change to anotherstation.

One more unusual situation wasnot so apparent. While checkingthe DC voltages and waveforms ateach pin of IC300, we foundstrange symptoms when attachingtest equipment to pins 8 and 9.


Figure 1 Components of the SylvaniaE44 horizontal -sweep system are lo-cated at the right (as you face the rearof the TV receiver). The module hasthe sweep -oscillator, vertical -count-down, horizontal -countdown, hori-zontal -driver, vertical -drivers, andvertical -output circuits. The flyback ismounted on the chassis at the right ofthe module, while the tripler, safetycapacitor, and horizontal -output tran-sistor are mounted on the uprightmetal panel that serves as shield andheat sink.

These pins apparently are used inthe vertical count -down circuit tosupply a capacitor that is too largeto include inside the IC (C318-.027). The symptoms varied some-what depending on which instru-ment was attached. One measure-ment produced a fast vertical roll,along with a decrease of height.Another test connection caused aloss of the raster.

These results do not indicate anyshortcomings of the circuit. Theyjust warn you of some nonconven-tional effects of attempting mea-surements in sensitive circuits.

CommentsAlthough failures of the dividers,

ICs, or the comparison circuit cancause loss of vertical sweep or arolling picture, this is not verylikely.

The factory states that the 31,468 -Hz oscillator is stable and has alarge pull -in range of about ±_6bars (normally, more than enoughto compensate for the usual amountof drift from aging components).So, chances of the horizontal oscil-lator needing a frequency adjust-ment are negligible. The oscillatorcoil does have an adjustable core,and it can be retuned, if necessary.(Ground testpoint "W"-which re-moves the sync-and adjust the

TP"W -

1C400

L420HOLD

3 SCREENCONTRCLS

CL3E

SC4'-J

TL.0

1C1OM

043:

R441

15

YOM:ELOCKET

EC4-30C)11.1PER

CONVESO: K=T

Figure 2 Locations of several horizontal -sweep components are shcwn bycontinued on page 34 arrows on the 02-41656-1 deflection module.

March, 1978 33

Servicing Sylvaniacontinued from page 33

W1

18 VPP

+25 V

.1VP P

W3

2VPP

cp200 0

15 K

+21VSUPPLY

100 pF

2.2VPP W5

10

POSITIVE HORIZPULSES FROM

BLANKER

8VPP

1.6V

CDI "AGC -11

8.9VDC .22NEGATIVE VIDEO TO Q202 RgOg

A .6V

3.3V

68 pF

3

1000

2VPP

5V470

680 K

22 K

10VPP

4

10.7V

+12.9 V

18K

18K0

18

-.039

+10.7 V

100 0

1800

HORIZ

SYNC

330 0 El.13V E

10 pF

SAWTOOTH

GENERATOR

lb PIN

IC400

NOISE NV

AGC

VIDEO AMP

SYNC SEP

220 KI180pF

1-` Ell 8VPP

- 2.4 V

F 18V PP

SYNC

31.46 8 -kHz OSC

+17.8V

2. 7V PP

15 't +1.2 V

10 K

2

10000

+5.8 V 12 3

68 pic

.01

750

1000

14

.001121

.5VPP .3.4V

---2.3VPP--4. HORIZ

HOLD

.5 2 V PP

68 pF .20.3V

+21V

+21V

68 giF

VV5\\\/VV6

W7

w8"5;119r ka"-

W9W9

W 0

°4*1.11


+25 V+4.5 V

220

ZENER

470

VERT5.4V PP

5

2.2 MD

.22

.1V 3

2.4V PPVERT

+4.5 V 12

.041

+.8V 13

470 K0

R2.4 VPP

VERT

+1.5 V -=

.22

11

MD

.2V 8

43 KO

.027

+.6V 9 +4.2V

+3. IV

LCI 8200 f?

0 ± .033SYNC

220 K

3VPPVERT

31 kHz

1000 014

820 K

+1.6 V

0 33 pF 4

22 K I1.2 V

VERT

FREQ

DIVIDER

1C300HORIZ &VERT

DIVIDER

HORIZFREQ DIVIDER

+2 V

2 HOR Z SQUARE WAVE 7

+1.6 V

3300

3.2 VPP

+4.3V

NEGATIVE VERTICAL0071 PULSES TO 0302

TO R440 AND BASE OF

Q404 HORIZ DRIVER

W20 4.6 VPP

Figure 3 Here is the schematic of IC400 and IC300, including circuits for AGC, sync, sweep oscillator,vertical countdown, and horizontal divider.

W15 VERT RATE

W16 VERT RATE

W17 VERT

W18 ..VERT

W19 HORIZ

W20 VERT

W20 EXPANDED VERTICAL

Figure 4 These waveforms are for thecircuits of Figure 3.

March, 1978


35


core of L420 until the picturemoves upright and slowly across thescreen. Remove the ground from"W". That's all.)

This completes the preliminaryexplanations, so let's continue withan examination of circuit functions.

Horizontal -Phase DetectorAs we discuss the phase detector,

oscillator, and divider circuits, referto Figure 3 for the schematic, andto Figure 4 for the waveforms.Remember that the DC voltageswere measured accurately with adigital voltmeter, and the resultsoften are shown to two decimalplaces. This does not mean that thevoltages must be maintained withinsuch critical tolerances to insure

proper operation. Undoubtedly,other individual chassis will varythe usual amount from thesereadings.

Two signals are required for allhorizontal -phase detectors. In thiscase, the horizontal -sweep pulsesfrom the blanker circuit enterIC400 at pin 7. An internal circuitchanges the pulses to sawteeth,which exit the IC at pin 8 beforethey pass through C423 and reachthe anode of phase -detector diodeSC426.

The other signal is negative -goinghorizontal sync that comes fromIC400 pin 6, is shaped by R413 andC421 before reaching the commoncathodes of SC426 and SC424.These diodes rectify the two wave -

Figure 5 The 90° phase differencebetween waveforms proves that C418(in Figure 3) is part of a tuned circuit.At the left is the waveform at pin 14 ofIC400; the waveform at right camefrom the junction of C418 and L420.

3.2 VPP

FROM PIN 2

OF IC300

.8VPP

470 0 1B

+.48V E

HORIZDRIVER

55VPP

+24VHORIZDRIVER

W4

+53V 3VPP

.33

3300 Q

HORIZ DRIVER AND OUTPUT

250 uF

+37 V

HORIZ10 VPPOUTPUT

WS

r -J1220 VPP

FERRITE

BEAD

FERRITE

BEAD

Figure 6 This schematic includes the horizontal -driver, horizontal -output, flyback, andhigh -voltage circuits of the Sylvania E44 chassis.

Figure 7 These are the sweepwaveforms for Figure 6.

W1

VV2

W3

Vv n


Six adjustment controls along the rear identify the deflection module.The white rectangle in the upper -right corner is the HV tripler, and theflyback is beyond it.

+139V

470 Q BOOSTRECT

0 -.01I (2 kV)

+850 VTO SCREENCONTROLS

TO CONVERGENCE

124 TO 291

28 kVTO CRT

5 kVFOCUS

14.6 TO 5.81

TO TC24

CHROMAMODULE

W3

W5

W8

n In

forms, producing a small positivevoltage at the common cathodes.Therefore, the DC voltage betweenthe twc anodes is about zero, whenthe horizontal is locked properly.Any drifting of the phase betweenthe two signals unbalances therectifiers, and the DC voltagebetween the two anodes no longer iszero. Notice that the anode ofSC424 is not grounded (as itprobably would be with tube cir-cuits), instead this point is suppliedwith slightly less than +11 volts bypin 11 of IC400.

The correction DC voltage at theanode of SC426 is filtered by 8421and C424 before it is applied to pin10 of the IC. Evidently, the DCvoltage reaches the oscillator tran-sistor inside the IC, varying thefrequency when needed.

This phase detector is nearlyconvertional, and it is suppliedwith 15,734 -Hz signals, althoughthe oscillator operates at 31,468 Hz.

Sync And AGCNegative -going composite video

enters IC400 at pin 3. Inside theIC, automatic noise inversion re-moves most noise pulses before thevideo goes to the AGC keyer and tothe sync separator.

Sync separation appears to beconventional, with the componentsbetween pins 4 and 5 shaping thevideo for proper clipping. Noticethat testpoint "W", that's used forremoving the sync during oscillatorfrequency adjustments, is located inthat path. Pin 5 measures about+0.8 volt when the IF cable isunplugged to remove all snow andsignals, about -0.1 volt for snowwithout a station, and varies around-2.5 volts with a normal signal andpicture. These readings are nearlyidentical to those in transistorizedsync -separator circuits.

A single AGC voltage comes outat pin 1. This is a positive voltagethat becomes more positive with astronger station signal. A transistoron the IF module amplifies andinverts the AGC voltage beforesending it to the tuner RF stageand to the IF transistor. Details ofthose circuits will be presentedwhen we analyze the IF section.


March, 1978 37


OscillatorTransistors for the 31,468 -Hz

oscillator are inside IC400, makinga thorough analysis impossible.C418 and L420 (hold control)comprise the oscillator tuned circuit.

Incidentally, dual -trace wave-forms allow us to prove that C418is part of the tuned circuit, and notjust a DC -blocking capacitor (seeFigure 5). The phase shift across acapacitor in a series -tuned circuitalways is 90°. The near -sine waveat the L420 end of C418 has largeramplitude and lags 90° the moredistorted waveform at the pin 14end of C418. Also, the two ends ofthe series -tuned circuit (pins 13 and14) are in phase. This proves thatan equal and opposite phase shiftexists across L420. Therefore, L420and C418 make up the tunedcircuit that determines the free -running 31,468 -Hz oscillator fre-quency.

Output of the oscillator at pin 1

is a squarewave signal, which isconnected to pin 1 of IC300, the ICwith the dividers and digital logic.

Sweep DividersVertical and horizontal sync from

IC400 is reduced in amplitude and

filtered slightly by R302, R304, andC304 before it enters IC300 at pin4. It is believed this feeds the logiccircuitry that selects the type ofvertical locking, according to thetype of signal.

Also, the same sync is integratedby R306 and C306, leaving verticalsync pulses. These pass throughC301 and R308 to pin 14 of IC300.It seems likely that the vertical syncpulses are used by the logiccircuitry to establish the correctstarting point of the vertical -fre-quency signal that's sent to thevertical sweep circuit. In any event,loss of sync at pin 14 allows thevertical to roll sometimes.

Many of the other IC300 pinsbring in proper DC voltages. Fourpins are used to filter waveforms orconnect large external capacitors tothe internal circuits. Pins 12 and 13have vertical waveforms (see Figure4). Pins 8 and 9 also have DCvoltages and waveforms, but theyare very sensitive to the addition ofexternal capacitances, such as scopeand meter leads. This was explainedin the preliminary discussion.

Narrow negative -going vertical -rate pulses emerge from IC300 atpin 7. In Figure 4, the pulses are

Figure 8 Defects of diode SC440change the waveform at the collectorof 0404. The top trace is thetriangular waveform caused by ashorted SC440; and the ringing wave-form of the lower trace is produced byan open SC440.

shown in the conventional way, andthen expanded. Small -amplitudehorizontal pulses broaden the baseline and the pulse tips of thevertical waveform.

Horizontal Driver And OutputRefer to Figure 6 for the driver

and output schematic, and toFigure 7 for the waveforms.

Horizontal square waves (of 50%duty cycle) come out of IC300 atpin 2, and they go through R440 tothe base of Q404, the horizontal -

After a couple of screws are removed, the metal panel can be movedor laid down at an angle, allowing access to the flyback.

0406 (at left), the horizontal -output transistor, is mounted in a socketon the outside of the metal panel.


OPTIMA VALUE SALE

driver transistor. C432 is connectedfrom base to ground to filter thewaveform slightly.

DC waveforms show that thesquare waves from IC300 are theonly forward bias for Q404. Zerovoltage is at the bottom of thesquare waves; therefore, the peak -to -peak amplitude is exactly thesame as the maximum instan-taneous forward bias (about 0.8VPP).

Square waves at the base producesquare waves at the collector ofQ404 (which is a plastic -typeTO -22 intermediate -power transis-tor). Ringing is minimized at thedriver transformer (T440) by diodeSC440. The diode conducts at thebeginning of each square wave,thus charging C436. When thesquare wave amplitude decreasesslightly below the voltage of C436,SC440 is reverse biased, and stopsconduction, permitting a smallamount of ringing by T440. Actu-ally, SC440 and C436 are a peak -reading rectifier circuit. R442 bleedsC436 moderately fast, so the voltageof C436 will be lower at the start ofthe next square wave. This causesSC440 to draw a heavier current,load T440 more, and thereforedamp the ringing more effectively.

One peculiarity of the circuit is

that the "rectification" of SC440produces a higher DC voltage atC436 than is available at the powersupply! Look at it this way: if thecollector load of Q404 was aresistor (rather than a transformer),the collector voltage would changefrom zero (during saturated con-duction) to the supply voltage (whencut oft). In this case, the supplyvoltage is +25 volts (because thesquare -wave voltage drop acrossR444 is averaged -out by C438, thefilter. Therefore, the maximumpeak -to -peak voltage at Q404'scollector would be 25 volts.

With the transformer operatingas the collector load, the measuredcollector voltage was 57 volts peak -to -peak. This proves that trans-former ringing is supplying theextra 32 volts! When SC440 isopen, the collector waveform has ahuge amount of ringing (Figure 8),although the picture is not affected.

(Of course. it's possible that theexcessive ringing might overload theoutput transistor, causing an even-tual failure. I suggest checking thisdiode and the collector waveformbefore you install a replacementoutput transistor.)

On the other hand, a shortedSC440 changes the collector wave-form to triangles (Figure 8), and thepicture is dark with a large foldoverin the center of the raster.

Horizontal Output CircuitsThe horizontal output and fly-

back circuits of the E44 are similarto those Jof some other models, sotroubleshooting will be about thesame.

However, a few of the waveformsare slightly different. L438 is addedat the low end of the T440secondary winding, and this changesthe base waveform of Q406. Otherwaveform variations occur becauseof the two ferrite beads that areadded to the wire between theemitter of Q406 and C444 (thefour -legged safety capacitor). Q406,the horizontal -output transistor is

mounted on the right side (as youface the rear of the receiver) of thechassis. The metal panel can beloosened and moved out at an angleto provide added room for diagnosisor parts replacements.

Ferrite beads on a wire force thewire to act as though it is a smallinductance. It's better than a chokein many circuits, however. becauseit does not have any self -resonance.This means it can't ring whenshock excited. A fast -rise -timesquare -wave current through such awire/bead circuit would show nar-row positive- and negative -goingvoltage pulses at the edges of thesquare waves.

The same thing happens here.The beads cause pulses in the0406 base waveform, at the coldend of the base winding, and at theemitter. In fact, I was surprised tofind negative 30 -volt pulses at theQ406 emitter, even though theemitter path goes only through thebead/wire and the foil of the safetycapacitor before reaching ground.It does illustrate that perfect


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March, 1978


39


grounds are not possible. When thebeads were removed from the leadof C444, the amplitude of thepulses went down to 2 VPP.

Of course, these unusual pulsesare normal for the circuit, and theyare not harmful to the transistors. Imention the situation only to ex-plain about the beads, and so youwill not believe the pulses indicate adefect, when you see them duringtroubleshooting.

Boost supplyOnly one voltage supply comes

from rectification of the horizontal -

sweep pulses. Diode SC445 andC448 perform peak -reading rectifi-cation of the positive pulses ofhorizontal sweep, producing about1050 VDC that is reduced to +850volts for the screen (G2) controls.

Flyback operationIn addition to the primary, the

T400 horizontal -output transformerhas only two more windings. One isfor the high -voltage tripler (whichalso supplies the focus voltage), andthe other is a 330 VPP source ofhorizontal (for the convergencecircuit) and blanking (for theservice switch during set-up ad-justments).

The yoke current does not comefrom the flyback, but the yoke isconnected to the collector of thehorizontal -output transistor, and itreturns to ground through theside-pincushioning transformer andand C348.

Technical questionWhile measuring the DC voltages

around the horizontal -output stage,I was amazed to find the DCvoltage at the collector of 0406(output transistor) measuring higherthan the supply voltage. Aftermaking a few more measurementsand looking at an unusual wave-form, I found where the extravoltage came from.

Can you explain how the Q406collector DC voltage can measurehigher than the voltage source?

Yoke And Pincushion CircuitsFigure 9 shows the schematic of

the horizontal yoke and the side-pincushioning circuits.

Excessive width of the picturenear the top and bottom of theraster is corrected by varying aninductance that's in series with thecold side of the horizontal yoke.

Specifically, the hot end of theyoke is connected to the collector of

1220 VPP 44VPP

FLYBACK

PIN 8

HORIZ YOKE

6

+139V

+ 33V

4

2.8VPP 30VPP

FROM VERTSWEEP20uF +2V Am

SIDE PIN

L-3

1.7VPP

+ 4.5 V

100µF

Figure 9 The side-pincushioning circuit has this schematic.

Q406 (after C444). The cold end ofthe yoke goes through windings ofT350 before being bypassed toground by C348.

Vertical -sweep voltage from thecold end of the vertical -convergencesystem is filtered by R370 andC352. (See the waveforms in Figure10.) At C352, the waveform isroughly a sawtooth, which causes aparabola of current through thecenter winding of T350. A smallDC current from R366 provides thecore magnetism that's necessary forproper operation of the saturable -reactor transformer (T350).

The vertical -sweep currentthrough T350 changes the in-ductance of the windings carryingyoke current, so the inductanceincreases during times the sweep isat the top and bottom of the raster.This reduces the width more at thetop and bottom than it does nearthe vertical center of the raster.Therefore, the side pincushioning iseliminated.

Next MonthVertical -sweep circuits and the

operation of the IF stages (in-cluding the IF AGC) will be thesubjects of our Sylvania analysisnext month.

VV1

Figure 10 These are the waveforms ofthe pincushioning circuit of Figure 9.


LSam Wilson's

Technical NotebookBy J. A. "Sam" Wilsor, CET

Measuring Resistors "In Situ"My dictionary defines "in situ"

as "in position" or "in its originalplace." Therefore, this discussion isabout the measurement of re-sistances in -circuit, without discon-necting them first.

Diode resistance varies with voltageRegardless of the equipment or

the method used, all resistance

measurements involve applicationof a voltage to the circuit undertest. This voltage changes with theresistance value, and it is differentfor eac`i resistance range.

Those changing voltages are thereason why the resistance of a diode(or a transistor junction) dependson the type of meter circuit and onthe range selected. For example,the base/emitter junction of a


Sam Wilson's monthly "Tech-nical Notebook" will present avariety of subjects and ideas.Sam has strong opinions, andpossibly some will provokeconversation and controversy.The ideas and opinions of thiscolumn are not necessarilythose of the editor or otheremployees of Electronic Ser-vicing.

Your letters are welcome, solong as you give us permissionto quote from them. Addressall letters to:

J. A. "Sam" Wilsonc/o Electronic ServicingP.O. Box 12901Overland Park, Kansas 66212

C.)NPN

TRANSISTOR.E

TWO PARALLEL

RESISTANCE PANS

Figure 1 Conduction of diodes (or the junctiols of transistors) add non-linearresistances that cause errors during in -circuit resistance tests.

March, 197841

Technical Notebookcontinued from page 41

germanium transistor might meas-ure 5 ohms when the X1 range of aVTVM was used, 29 ohms for X10,170 ohms for X100, and 1,000ohms with the X1000 range. Theohmmeter is not producing wrongresistances. Instead, the diode ischanging forward resistance ac-cording to the actual voltage ap-plied to it.

Not all ohmmeters apply thesame voltage. Therefore, diodes andtransistor junctions will measuremany different resistances accord-ing to the type of meter.

Circuit paths through diodesProblems begin when a tech tries

to measure the value of a resistorthat's in a circuit along with adiode or a transistor junction(Figure 1). Because diode resistancevaries with the applied voltage, it'snot possible to assign a definiteresistance to each diode. As shown,the base resistor and the B/Ejunction of the transistor are inparallel. So, the ohmmeter currentflows through both. The diode con-duction causes an erroneous read-ing, which varies with the rangeand with the type of meter.

Low -power ohmmeter readingsSome late -model meters (particu-

larly multimeters) offer "low -

power" ohms functions. The maxi-mum voltage is kept below theconduction point of silicon diodesand transistors. Therefore, "in situ"resistance measurements can bemade without many errors from thesilicon diode -or -junction resistances.Of course, circuits with extremely-

high resistances might show someerrors, but other circuits can betested accurately.

On the other hand, germaniumdiodes and transistor junctions canconduct with less than 0.1 voltapplied. If germanium devices arein the circuit, use additional pre-cautions.

Reversed voltagesAnother effective method of

eliminating nearly all of the errorsfrom diode and junction conductionis to take a reading, and thenreverse the test leads before making

the same measurement again. If thetwo resistance readings are identi-cal, there's little chance of errorsfrom diode conduction. When thetwo readings are very different, thehigher reading will be more ac-curate.

This method has some limita-tions. For example, circuits havingtwo or more semiconductor devicesmight have leakage through a diodeduring the test with one polarity,and leakage through a transistorjunction when the polarity is re-versed.

Combining the low -power ohmsfeature with the reversed -voltagemeasurements should eliminatemost diode -conduction resistanceerrors.

Resistances in parallelNeither of the previous methods

can measure the individual resistorsof Figure 2. Any ohmmeter willread the resistance of RI in parallelwith the sum of R2 and R3.

One solution is to determine theproper resistances (from a sche-

matic or the color codes of theresistors), calculate the total resist-ance, and measure the actual re-sistance with your ohmmeter. If thecalculated and actual resistancesare equal, it's likely all three re-sistors have the correct values. (Ofcourse, that's assuming the resistorsdo not have widely different values.For example, if one resistor is sup-posed to have more than 10 timesthe resistance of the other two, anopen in the large resistor would notchange the total resistance readingenough to be significant.)

If the measured resistance isincorrect according to the calcu-lated value, one of the threeresistors must have a wrong value.

To calculate the resistance of thecombination, use this formula:

R= RI X R2 ± RI X R3RI ± R2 R3

If you have an electronic calcula-tor, it's easy to do the math. Analternate method is to add theresistances of R2 and R3. Then use

ma& HOW CAN RI BE

MEASURED ACCURATELY'

Figure 2 Combinations of series and parallel resistors make in -circuitresistance tests more difficult. One way is to calculate the correct value ofthe combination and compare that with the total measured resistance. Anysignificant variation between the two figures suggests that one of theresistors has a wrong value. As a last resort, R2 and R3 can bedisconnected at point A. This allows testing of all three resistors with aminimum of unsoldering.


0

0

that value and the resistance of RIin the formula for two resistors inparallel.

If these tests indicate a wrongresistor value, open the circuit atpoint A. and test each resistorseparately.

Use a bucking voltageFigure 3 shows a way of meas-

uring RI, without errors from R2and R3. Connect a variable -voltagesource to the junction of R2 andR3, and adjust the voltage until itis exactly equal to the ohmmetervoltage that's at the R2 end of RI.This places equal voltages at bothends of R2, thus eliminating allcurrent through R2. The zero R2current gives the same effect as anopen R2, which breaks the R2/R3path that parallels RI. The ohmme-ter now reads only the resistance ofRI.

Editor's Note: I tried this test byusing the ohmmeter function of aVTVM and found the method to bevalid. However, the balancing of the

two voltages was so critical that adigital meter was required to de-termine when the two voltages wereequal. This matching of voltages ismade difficult also by the ohmme-ter voltage changing as the variablevoltage is adjusted. For example. asthe variable DC voltage was in-creased from zero, the ohmmetervoltage across RI increased, alongwith the resistance reading. Whenthe variable voltage is less than theohmmeter voltage, the RI resist-ance reading is too low. At theother extreme, a variable voltagethat is higher than the ohmmetervoltage produces RI resistancereadings that are too high.

Tuning By Resistance ChangeLast year, I was in Indianapolis

at an ISCET board meeting. I haddiscussed the resistance -tuned cir-cuit of Figure 4 in a previous issueof my Technical Notebook, andseveral technician friends were giv-ing me a hard time about it.

In the article, I pointed out that

VARIABLE

DC VOLTAGE

METHOD OF MEASURING RI

"IN SITU"

Figure 3 Specific resistors in a series -plus -parallel configuration often can beisolated for test by applying a bucking voltage that is equal to the DC voltage

applied by the ohmmeter.

varying either the resistance inseries with the capacitor or theresistance in series with the in-ductance would change the reso-nant frequency of the tuned circuit.The first question from a "friend"was, "So what?" A question likethat is nearly impossible to answer!

Another tech asked if the circuithad any practical uses. I couldanswer that question. It has beenused in automatic frequency -controlcircuits. Also, it is useful for ad-justing low -frequency filters wherethe capacitance value is so highthat a varactor diode won't work.

But the next comment stoppedme cold. One man said that thechange of frequency is too small tomerit any discussion.

Although I knew the basic theorywas correct, I never had calculatedthe amount of change before. Nowwas the time to use my calculator.

The equation for the resonantfrequency of parallel capacitanceand inductance when there's resist-ance in the circuit is shown inFigure 4, along with the schematicand values of the circuit.

In schools, there is an unfortu-nate tendency to ignore the general(complete) equation. Instead thispartial equation is given for parallelresonance:

Fr =2n VLC

Actually. this is a special -caseequation that is correct only whenthe resistances of the inductor andthe capacitor are equal, or whenthe two resistances are smallenough to be ignored.

The general equation is impor-tant because it shows that the valueof a resistance in series with eitherthe inductor or the capacitor of aparallel -tuned circuit will affect theresonant frequency.

Incidentally, there are two re-

sistant conditions that completelyeliminate all resonance. In thegeneral equation for parallel reso-nance, if the inductor resistancesquared times the capacitanceequals the inductance, the numera-


March, 197845


1 VRL2C-LFr =

2n LC ReC-L

NOW DO THE VALUES OF RL

AND Rc AFFECT THE RESONANT FREQUENCY?

Figure 4 A resistance added in series with the inductance or aparallel -tuned circuit reduces the frequency of the resonance point. Aresistance added in series with the tuning capacitor increases the resonantfrequency.

100

90

80

83.482.34/ / 79.08

73.3

64.3770

50.6RESONANT 60

FREQUENCY

IN KHz 50

40

30

20

10

0 I I I I I

0 5 10 15 20 25

RL RESISTANCE IN OHMS

Figure 5 This graph shows the calculated change of resonance (in thecircuit of Figure 4) when the resistance that's in series with the coil isvaried from zero to 25 ohms.

tor becomes zero, thus making theresonant frequency zero. This indi-cates that larger inductor resis-tances lower the resonant frequen-cy.

Also, if the capacitor resistancesquared times the capacitanceequals the inductance, the resonantfrequency is infinite. This indicatesthat increasing the value of thecapacitor resistance raises the reso-nance frequency. In both of theseexamples, there is no resonant fre-quency. Compare this with seriesRLC tuned circuits that alwayshave a resonant frequency.

Back to the mathematical proof.I chose the values shown in Figure4 and calculated in 5 -ohm stepsfrom zero to 25 ohms for theresistance in series with the in-ductor. These are the results:

InductorOhms

FrequencyIn KHz

0 83.405 82.34

10 79.0815 73.3020 64.3725 50.60

A graph of these values is shownin Figure 5. Notice that 25 ohmsreduces the frequency from 83.4KHz to 50.6 KHz, a decrease of32.8 KHz (or 39%).

If you're designing an electronicbuggy whip, this might be just thecircuit you need.

Caution About Strobe LightsRepeating strobe lights can trig-

ger an epileptic seizure. For ex-ample, a Colorado electronicsteacher had his students build asimple electronic strobe light. Whilethey were testing it, the rapidflashing started an epileptic seizurein one of the students.

To cause the problem, the repeti-tive frequency must be slow enoughto be seen as individual flashes oflight.

After I heard of this incident, I

researched the subject and foundthat almost any repetitive low -fre-quency energy seems to do thesame thing. Other triggers are

O

O

O

O


O

O

windshield wipers (especially undercertain kinds of street lights),shower sprays, and rapidly -flashingneon signs.

Advise any epileptics to avoidlooking at flashing lights or re-peated movements of any kind.

Sound SicknessVery low -frequency sounds can

cause fatigue or nausea. The soundlevel must be high, and the fre-quency should be around 10 Hz,although the critical frequency de-pends on the individual person.

Could the constant thumpingnoise of car wheels passing over thetar strips of a pavement be the realcause of "car sickness"?

Also, think about the low -fre-quency beats caused by intermodu-lation distortion in a hi-fi systemthat is operated at loud soundlevels. Could they be the cause offatigue, which is the first stage of

Onausea?

Inserting IC PinsHave you ever had trouble insert-

ing all of the pins of DIP ICs into asocket at the same time? Well, itcan be an exasperating job, thatoften results in bent pins.

Try this tip: insert all the pins inone side of the socket; then, use astiff rectangle of plastic or card -

O

0

board to gently bend the other rowof pins into line with the socketholes (see Figure 6). Usually thislast row of pins will slip easily intoplace, when they are all moved atonce. Finally, press down gentlywith your fingers on top of the IC,to seat all of the pins tightly.

Protect CMOS ICsThe manufacturers of CMOS ICs

have nearly solved the problem ofgates being destroyed by staticvoltage charges. Zener diodes areconnected from the leads andcommon inside each IC. Voltagesthat are higher than the zenerrating cause the zener to conduct,thus reducing the transient highvoltage to a harmless value.

Caution: If you build or repair adigital clock that has CMOS ICs,be very careful and use all of theusual MOSFET precautions. Many(perhaps most) CMOS clock chipsare NOT protected.

Mystery Of The Magnetic PolesIf you give me the slightest en-

couragement, I'll readily launchinto stories about the brilliantstudents I've taught, and the cleversolutions they have found fordifficult electronic problems.

But one problem has defied theirbest efforts so far, although it

IC

INSERT IC PINS INTO SOCKET

WITH A STIFF CARD

PLASTIC OR

CARDBOARD

I

Figure 6 To make installation of ICs easy, insert all ofthe IC pins of one side into the socket. Then, slightlybend all pins of the other row toward the body of theIC, using a rectangle made of plastic or stiff card-board. These pins should slide easily into the socket.

appears to be very easy. Here arethe conditions: magnetize a 3 -footlength of steel welding rod so oneend has a north pole and the otherend has a south pole, but there areno other poles in between.

After you have magnetized therod, check your result by using asmall pocket compass. My studentshave tried to do this for so manytimes that I'm beginning to believeit can't be done. Figure 7 showswhat usually happens to the mag-netic poles.

Technician Shortage?You sometimes are told there are

too many electronic technicians. Atother times you hear about theshortage of technicians. (Or, is ittoo many short technicians?) I

heard of one who was really"short," and I'm not referring tohis height, but to his brain power.

This next event actually hap-pened in a Youngstown, Ohio, "Maand Pa" store. They needed a goodoutside technician, and advertisedin the local paper. Out of severalapplicants, they selected a man whoclaimed 27 years of experience.

The new employee had a coupleof unusual characteristics. Hewas built like a gorilla (about 260pounds), and he even looked a bitlike one in the face. But, who's tosay that large ugly people can't be


N

MAGNET, POLES IN WELDING ROD

Figure 7 man you magnetize a 3 -foot length of steelwelding rod so the north po.e is at one end, and a southpole is at the other end, but without any extra poles inbetween? Sams students always obtained several poles, asshown.

March, 1978 47


competent technicians? Also, it'snot smart to become unpopularwith the ugly -lib people.

Out of the eight calls he madethe first day, he brought in eightTV sets. He didn't pull the chassis,but brought in cabinets with all theworks. Now, these were huge con-soles that usually require two strongmen to lift them, but he carried oneunder each arm!

The "Pa" end of the business satdown with him and explained thatit wasn't a good practice to bring incomplete machines, especially sincemany of them suffered dings andscratches in the process.

"Fix them in the home. If theTV must be brought in for shopwork, bring only the chassis," Pasaid.

The new man went out on callsthe next day, with "Fix them in thehome" ringing in his ears. But,within an hour the first customerwas on the phone, and she wasMAD. "What kind of a fool outfithave you got there, you idiot?""Ma" got to field this problem. "Issomething wrong?" "Well, thatturkey you sent out to fix my set

took out all of the tubes, put themin a paper bag, and told me to godown to the drug store and testthem!"

After "Ma" calmed the customer,she turned to "Pa." "You get outthere and stop that nut, while westill have a business. Here's a list ofhis calls."

"Pa" (who probably weighed 140pounds, soaking wet) didn't dashfor the door. "Maybe we could justcall the customers..."

"Get him!"As he started out the door, "Ma"

called after him, "Pa!""Yeah?""And don't hurt him.'

Alternator QuestionThis request for information was

received from Brian Cook, CET: "Isit possible to cheaply rewire anautomobile alternator for use at lowRPMs?"

My answerMr. Cook, thanks for the letter,

and a special thanks for the self-addressed stamped envelope.

5 VOLTS

OR HIGHER

SUPPLYVOLTAGE

OPTICALCOUPLER

ti

SUPPLY VOLTAGE ACROSS AN LEO

PROVES IT IS OPEN

Figure 8 Two characteristics of LED circuits allow you to determine whetheror not an LED hidden inside an optical coupler is lit. Current -limitingresistors are necessary, and LEDs tend to act much like zener diodes tostabilize their voltage at a certain DC voltage. Therefore, if you measure thefull supply voltage at the leads of such an LED, it proves the LED is open(not lit). But if the rated DC voltage for that type of LED is measured at theleads. the LED is okay (emitting light).

The original battery -charging de-vice in cars was a DC generator.However, it had two inherentproblems. The first problem wasexcessive maintenance (brush re-placements and repairing the com-mutator). Secondly, generatorscould not produce a chargingcurrent when the engine was idled.

After the auto makers addedmore and more electrically -poweredequipment, better battery chargingwas necessary. Then came thechangeover to alternators, whichbasically are AC generators. Solid-state diodes are built inside thecase to rectify the AC power.

Alternators will produce somecharging power at idling speeds,without requiring any modification.

Perhaps you need increasedcharging current at slower -than -idleRPMs (your letter didn't say howyou wanted to use the modifiedalternator). If only slightly morecharging current is needed, youcould install a pulley of a smallerdiameter on the alternator itself.

Give me more details about whatresult you want, and the uses forthe increased current, and I'll try togive other answers. Or, perhapsanother reader of Technical Note-book can supply a better answer.Write to me in care of ElectronicServicing.

Is The LED Lit?Many optical couplers have an

LED to furnish light and a light-sensitive transistor to detect thelight. These couplers are installedinside light -tight enclosures. There-fore, you can't look at the LED todetermine if it's lit.

As shown in Figure 8, each LEDis operated through a current -limit-ing resistor from a voltage supplythat has several times more voltagethan is needed by the LED. TheLED can be tested by the tendencytoward regulation of the voltageacross itself. Many LEDs are ratedat 1.6 volts; therefore, a measure-ment of 1.4 to 1.7 volts across theLED leads proves the LED isemitting light. El

O

O

O

O

O


test eguipment p] 0_r-

Portable Digital MultimeterThe Leader Instrument Corpora-

tion's model LDM-851 digital multi -meter features pushbutton selectionof AC volts, DC volts, K -ohms,megohms, and DC milliamperes,plus a range button that providessemi -automatic high -range or low -range switching of the 16 ranges.Polarity indication for DC measure-ments is automatic.

A separate overrange indicationis located near the 31/2 -digit LEDdisplay. Overload protection oper-ates for all ranges.

Power is provided by four internal"C" cells for portable operation,plus an optional AC adapter that'savailable at extra cost. Test leadsare included, and model LDM-851sells for less than $200.


Function GeneratorB&K-Precision's model 3010 low -

distortion function generator offerswide frequency coverage spanning0.1 Hz to 1 MHz in six ranges, witheach range providing a linear 100:1frequency control. The unit gener-ates sine, square, TTL square, andtriangle waveforms.

Range and function selection ispushbutton -controlled for fast oper-ation. Frequencies originate froma voltage -controlled oscillator (VCO),which can be varied over eachrange by the front -panel frequency

control or by the VCO externalinput. When a 0 to 5.5 V ramp isapplied to the VCO external input,model 3010 will provide a 100:1frequency change to serve as asweep generator for response mea-surements in audio and IF circuits.

The unit also features a variableDC offset control, which provides upto ±.5 VDC (into 600 ohms) that iscombined with the selected audiosignal.

For square -wave operation, the3010 offers both a fixed TTL outputlevel for digital logic applicationsand a variable -amplitude output forother measurements.

The unit is priced at $175,including a detailed instruction man-ual.


ScopeBCD's new model 480 solid-state

triggered -sweep oscilloscope wasdesigned for testing TV receivers.and other electronic equipment.

Model 480 has DC to 10 MHzvertical bandwidth, AC and DCcoupling, 11 -position calibratedattenuator, 10 mV/cm sensitivity,and pushbutton operation.

A built-in TV -sync separator al-lows easier troubleshooting of videowaveforms. Frame or line triggeringis selected automatically by thescope in conjunction with the sweepspeed setting. The calibrated timebase helps to identify unknownfrequencies. A fully regulated powersupply provides stable voltages re-gardless of line and load fluctu-ations.

Price of the factory -assembledscope is $425.


Features of these products were suppliedby the manufacturers, and are listed at nocharge to them. If you want factorybulletins, circle the corresponding numberon the Reply Card, affix a stamp, list therequired information, and mail the card.

APPLIANCEREPAIRBOOKS

100,416.0

Thirteen Handbooks written in easy -to -under-stand language by experts in the service fieldwith illustrations and diagrams, Acclaimed byinstiuctors and professionals alike, How todiagnose and repair air conditioners. refrigera-tors. washers. dryers. ranges, microwaveovens. dishwashers, vacuum cleaners, electro-static air cleaners. RV gas appliances, hairdryers, motors. water heaters, coffeemakers.can openers. floor polishers. steam irons, foodmixers. lawn care appliances. electric knives.electric and digital clocks and many othersAlso fundamentals of solid state, setting up ashop using test instruments and more Only$2.65 to $4.90 ea.

SEND FOR FREE PRICE LIST

Gamit, Dept. ES5841 W. Montrose Avenue

Chicago, Illinois 60634


ELECT.

4.1"

nl

WE'RE GROWING!to better represent

YOUthe successful servicebusiness operator.

*Over 2500 firms belong*39 State Affiliates*167 Local Associations

YOU CAN JOIN!and learn how to makemoney and work less hours .

Write today for amembership applicationand more information.

1715 Expo LaneIndianapolis, Indiana 46224

Phone (317) 241-8172

March, 1978 49

It's the one and only flat -rateincrement system that gives youthe great feeling of pricing everyjob right. A system that treatsboth customer and shop ownerfairly. Fast finger -tabs in botheditions: 6x9 Hard Cover, steelring -bound - $19.95 ea. post pd.

Or The Satellite Editionfor pocket sized con-venience - $16.95 ea.post pd.

NewComputerizedParts Pricingmanual listsover 3.500most -usedparts - $75initial set-upplus $10per copy.

P.O. Box 5234Lincoln, NE 68505

tv &rodiotech's guideto pricing

Nebr residentsadd sales tax

Sperry tech inc. (No. editions)1My check enclosedBankAmencard Exp.

_ Master Charge ExpNameCoAddressCityState 71p

For More Details Circle (13) on Reply CardJ

Volksmeters forSunny Days!

Now with LCD'sAND longer battery operationAND now less than $100

LM -300 3 digits $99.50LM -350 31/2 digits $125.00Features Include: Measures VDC, VAC, DCmA, ACmA (fourranges each) and ohms (five ranges). Autoze ro, auto polarity and overload Indication. DC accuracy - LM -300: 1%; LM -350: 0.5%. Input protection. Small size: 1.9" H x2.7" Wx 4.0" D. Optional NiCad batteriesand charger unit available at extra cost.

Non -Linear Systems, Inc.Origmator of fhp rhydal voltmeterBox N. Del Mar. Calolorma 92014Telephone (714) 755 1134 MX 910.322 1132


aroductuN

CB AccessoriesWinegard has made available a

mobile CB antenna and accessoryself -merchandiser package. Therack, model ID -500, includes twoeach of 17 different products. FourCB antennas: trunk -lip mount mod-els, TL -100 and TL -300; roof/deckmount model RM-100: and magnet -mount model MG -100 are featured.The remaining products are mount-ing -hardware replacement parts andvarious types of stainless -steelwhips. A rack with 100 CB -antennastuffers is included.


Electronic Siren DriverMountain West is featuring an

electronic siren driver which hasvariable sweep rate and sweeprange.

This adaptable siren driver is foruse in alarm systems where sirentone and whooping or sweep ratemust be varied. Often required tomake siren output distinct frombackground noises, this driver canbe connected to produce either asteady or a sweeping tone asneeded.

Rate can be varied from .1 -secondsweep to 6 -second sweep. Range isfrom 2500 Hz to 400 Hz. The circuitboard fits easily in a control box.

The unit comes with connectinginstructions and is priced at $49each.


Packaging TesterITT Pomona Electronics has de-

signed the "Micro -Grabber" fortesting high -density packaging.Model 4233 is 1.53 inches long anduses a plunger action between thethumb and two fingers.

Made of molded glass -filled nylon,it withstands 240°C at 400/0 R.H.Other features include a stainless -steel spring, beryllium -copper con-tact, and gold plating.


SERIOUS ABOUTYOUR FUTURE IN HOMEELECTRONIC SERVICE?

The Sign ofProfessional

Service

... a not for profit associationchampioning independents' rightto compete, and delivering valu-able benefits continuously since1950.

NATESA offers low cost groupinsurance, discounts on everythingfrom eyeglasses to motor vehicles,individual consultation on particu-lar problems, representation togovernment and industry at alllevels and a place to unite to pro-tect each individual member withthe strength of all.

Send this ad with your card orletterhead to:

NATESA, Dept. ES5908 S. Troy St.Chicago, II. 60629

El Membership. $60.00 enclosed.As our member premium, pleasesend free .

CI Practical Business Manual- OR -

0 Service Contract Manual

A Public Service of this nilmagazine & The Advertising Council MO

We'recounting

onyou.

Red Cross.The Good Neighbor.

IT'S NO PUZZLE IP

TO ORDER

OELRICH SERVICE FORMSFOE 1Y -RADIO AI I WAY MOM um( LEGAL FORMS FOR CALIF. FLA.UTAII NOW AT TOUR PARTS MIER OR WRITE FON CATALOG B64

OELRICH PUBLICATIONS4040 N NASHVILLI AVE. CHICAGO. ILLINOIS 60534


ELECTRONIC SERVICING50

Producipm

Fuse HolderA new coil -spring fuse holder by

Oneida minimizes the need for themore expensive pig -tail fuses andthe cutting and resoldering of pig-tail leads. The permanent devicealso does away with the need to pulla chassis or tuner for fuse replace-ment.

The fuse holder is constructed oftempered spring steel with dip -sold-ered leads. It comes five -pair perpackage on dealer cards; it also isavailable in bulk for OEM use.


RectifiersElectronic Devices has added a

series of half -wave, high -voltagerectifiers designed for B&W andsmall -screen color television sets.The diodes are available with rat-ings of 22 KV, 30 KV and 35 KV.Average forward current is 2.2milliamperes.

Two mounting styles are avail-able. Series TVS has end caps, andseries TVSL has wire leads.


Bolt CutterAn improved bolt -and -rod cutter

that will cut threaded fasteners toany desired length (down to 3/16"under the head) is available fromSentinel Tool Works.

Bolts of sizes from #4 to 3/8"diameter can be cut off, for thecutter is said to be made ofhardened tool steel which can beresharpened.


Features of these products were suppliedby the manufacturers, and are listed at nocharge to them. If you want factorybulletins, circle the corresponding numberon the Reply Card, affix a stamp, list therequired information, and mail the card.

Seeking Original Japanese Replacement

Parts for CB and Stereo Repair Use?

SEE US AT THE 1978 WINTER CONSUMER ELECTRONICS SHOW INLAS VEGAS JANUARY 5-8

CB REPAIR PACKAGE$63.00 value for only $39.95

Contains 2 each. Repair almost all CB Sets.2S8 405 2SC 1014 2SC 13072SC 710 2SC 1173 2SC 16782SC 756 2SC 1226 2SD 2352SC 828 2SC 1239 TA 7205P2SC 945 2SC 1306 BA 511

SPECIAL PACKAGE OF MOSTCOMMON DRIVERS 8 FINALS

This kit contains 6 each of.2SC 1678 2SC 75625C 1018 2SC 7992SC 1226 2SC 123925C 1306 2SC 13075145 00 value for Just $99.95

Original Japanese Transistors. FET, IC. DiodesCHECK OUT OUR LCW PRICES!

TRANSISTORS 2SA 839 2.15 2SC 454 .59 2SC 898 4 40 2SC 1478S 70 2SD 388 3.402SA 49 .59 2SA 841 .59 2SC 458 .59 2SC 900 59 2SC 1509 1.10 2SD 424 8.502SA 70 1.10 2SA 847 59 2SC 460 .59 2SC 929 .59 2SC 1584 8.50 2SD 427 2.802SA 101 .59 254 850 70 2SC 461 .59 2SC 930 .59 2SC 1586 6.60 2SD 525 1.60

2SA 102 .59 2SA 872A .59 2SC 481 1.60 2SC 943 1.20 2SC 1624 1.30 2SD 526 1.102SA 234 .59 2SA 908 11.00 2SC 482 1.50 2SC 945 59 2SC 1626 1.10 2SD 555A 6.602SA 342 .90 2SB 54 .59 2SC 485 1.60 2SC 959 1.50 2SC 1628 1.30 2SD 610 1.90

2SA 353 .70 2SB 55 1.10 2SC 486 1.60 2SC 971 1.00 2SC 1647 59

2SA 377 2.00 2SB 75 59 2SC 493 3.90 2SC 983 1.00 2SC 1669 1.60 FET

2SA 440 90 2S6 77 59 2SC 495 1.00 2SC 984 .90 2SC 1674 .59 2SK 19 1.602SA 483 3.00 2SB 186 .59 2SC 497 1.60 2SC 100061. .59 2SC 1675 .59 2SK 30 .902SA 484 2.50 2SB 187 .59 2SC 509 90 2SC 1014 1.20 2SC 1678 2.25 2SK 33 1.10

2SA 4852SA 489 10

2.600. 2SB 2022SB 220

1.60.70

2SC 5172SC 535

3.95.70

6C 10172SC 1019

1.401.20

2SC 16822SC 1684

.45

.592SK 342SK 40

1.10.70

2SA 495 70 2SB 303 .59 2SC 536 .59 2SC 1030C 2.80 2SC 1708 .59 2SK 49 1.302SA 496 1 10 2SB 324 .70 2SC 537 59 2SC 1047 .70 2SC 1728 2.00 2SK 55 1.302SA 497 1 60 2S8 337 1.60 2SC 538A 70 2SC 1060 2.25 2SC 1760 2.00 2SK 68 1.302SA 509 70 2SB 367 1.50 2SC 562 2.15 2SC 1061 1.40 2SC 1775 .45 3SK 22 2.552SA 525 250 2SB 3688 2.15 2SC 563 1.10 250 10613 4.40 2SC 1816 4.25 3SK 35 2.252SA 537 2 25 2SB 379 1.10 2SC 620 .59 2SC 1096 1.00 2SC 1885 .70 3SK 39 2.252SA 539 70 2SB 400 59 2SC 627 1 60 2SC 1111 3.40 2SC 1908 .59 3SK 40 2.252SA 561 59 2SB 405 70 2SC 632A .70 2SC 1115 3.40 2SC 1909 4.40 3SK 41 2.502SA 562 59 2SB 407 1 40 2SC 644 59 2SC 1116 4 40 2SC 1951 1.10 3SK 45 2.502SA 564A 59 2SB 415 .70 2SC 645 70 2SC 1116A 4.90 2SC 1957 1.20 MK 10 2.002SA 565 1.10 2SB 434 1.20 2SC 650 1.30 2SC 1124 1.30 2SC 1969 4.902SA 566 3 40 2SB 463 1.50 2SC 668 59 2SC 1162 1 10 2SC 1973 1.10 IC

2SA 606 1 90 2SB 471 1.60 2SC 680 2.80 2SC 1166 .59 2SC 1975 4.40 AN 2140 3.402SA 624 1.10 2SB 472 2.80 2SC 684 1.40 2SC 1173 90 2SC 2028 .90 AN 315 3.702SA 627 160 2SB 474 1 20 2SC 693B 59 2SC 1175 .90 2SC 2029 3.90 BA 511 3.402SA 628 .59 2SB 492 1.00 2SC 696 1.95 2SC 1177 14.00 2SC 2091 3.60 BA 521 3.702SA 634 .90 2SB 507 1.60 2SC 708A 1.90 2SC 1189 1.40 2SC 2092 3.90 HA 1151 3.702SA 640 .59 2SB 509 1.90 2SC 710 .59 2SC 1211D 70 2SC 2098 3.90 LA 4400 3.702SA 643 70 2SB 514 1.90 2SC 711 59 2SC 12'3 70 2SD 28 2.80 TA 7045M 3.002SA 659 .59 2SB 526C 1 30 2SC 712 .59 2SC 1222 .45 2SD 75 110 SN 7400 .192SA 663 4.90 2SB 527 1.90 2SC 717 .59 2SC 1226 1.00 2SD 90 1.60 SN 7490 602SA 666 .70 2SB 528D 1.60 2SC 730 4.40 2SC 1237 4.25 2SD 91 1.60 TA 7055P 3.002SA 672 70 2SB 531 3.40 2SC 732 .59 2SC 1239 3.50 2SD 92 1.50 TA 7060P 1.602SA 673 70 2SB 536 1.60 2SC 733 59 2SC 1279 70 2SD 118 3.00 TA 7061AP 1.902SA 678 .70 2SB 537 1.60 2SC 734 59 2SC 13116 4.40 2S0 130 1.20 TA 7062 1.902SA 683 .70 2SB 539 4.90 2SC 735 59 2SC 13117 4.90 2SD 142 2.00 TA 7205P 3.902SA 684 .70 2SB 541 4.40 2SC 738 .59 2SC 13'2 59 2SD 143 2.80 TA 7310P 3.952SA 695 .70 2SB 554 10.00 2SC 756 2.80 2SC 13'3G 59 2S0 178 1.40 uPC 592H2 1.602SA 697 70 2SB 557 3.40 2SC 763 59 2SC 1317 .59 2SD 180 2.50 PLL 02A 8.802SA 706 1.60 2S8 5618 70 2SC 773 .70 2SC 1318 .59 2SD 187 59

2SA 715 1 40 2SB 564 .90 2SC 774 1.60 2SC 1327 .59 2SD 188 3.00 DIODES2SA 719 .70 2SB 595 1.90 2SC 775 1 95 2SC 1330 1.50 2SD 205 1.40 IS 84 1.002SA 720 70 2SB 600A 7.00 2SC 776 2.65 2SC 1342 .59 2SD 217 4.40 15 188 452SA 721 .70 2SC 183 59 2SC 777 3.50 2SC 1344 59 2SD 218 3.70 IS 332 452SA 725 59 2SC 184 .59 2SC 778 3 60 2SC 1345D 59 2SD 223 1.90 1S 953 .452SA 726 59 2SC 281 .59 2SC 781 2.65 2SC 1359 1.40 2SD 224 1.90 IS 1007 452SA 733 59 2SC 284 1.40 2SC 783R 3.60 2SC 1360 1.00 2SD 226 1.60 IS 1209 452SA 740 2.65 2SC 367 .90 2SC 784 59 2SC 1362 .59 2S0 227 59 1S 1211 .452SA 744 3.70 2SC 369 .70 2SC 785 70 2SC 1364 1.40 2SD 234 1.00 I 1555 322SA 745R 4 40 2SC 371 .59 2SC 789 1.00 2SC 1377 4.90 2SD 235 1.00 ISS 1588 .322SA 747 5.80 2SC 372 .59 2SC 793 2.80 2SC 1383 59 2SD 287 3.70 IS 1885 .452SA 750 .59 2SC 373 .59 2SC 799 360 2SC 1400 .59 2SD 313 1.10 1S 2076 .45

2SA 756 3.40 2SC 374 .59 2SC 815 .59 2SC 1402 3.70 2S0 315 1.20 1S 2093 .452SA 758 5.80 2SC 380 .59 2SC 828 .59 2SC 1403 3.70 2SD 325 1.10 IS 2473 .456A 774 .59 2SC 381 .59 2SC 829 59 2SC 1419 1.10 2SD 3563 1.10 1N 34 252SA 777 1.10 2SC 382 .59 2SC 838 2SC 1444 2.80 2SD 3573 1.00 IN 60 .252SA 798 70 2SC 387 59 2SC 839 59 2SC 1448 1.10 2SD 358 1.302SA 814 190 2SC 394 .59 2SC 870 .59 2SC 1449 1.00 2S0 360 1.202SA 816 70 2SC 403 .59 2SC 871 59 2SC 1451 1.60 2S0 371S 2.802SA 818 1 40 2SC 430 1.10 2SC 897 2.65 2SC 1475 1.40 2SD 382 1.40

Nationwide / -

Ohio 800/582-1630

PRICES MAY CHANCE WITHOUT NOTICECOD ORDERS WELCOMED Less than $500 no deposit required

IMMEDIATE DELIVERY WITHIN 48 HOURS ON ALL TRANSISTORS IN STOCKMinimum order 510.00. Ohio residents add 4°. sales tax. Add Si 00 postage and handling

duantity discount prices. ASK FOR OUR COMPLETE PRICE LIST Manufacturer inquiries welcomed

ALL PARTS GUARANTEED AGAINST FACTORY DEFECT

TOLL FREE TELEPHONE:urs Mon -Fri. 10-7 Sal 11

FUJI-SVEA ENTERPRISE. don of Fuli-Svea Incorporated

Dept. ETP. 0. Box 40325 Cincinnati, Ohio 45240

For More Details Circle (15) on Reply Card51

nmarketalace

Advertising rates in the Classi-fied Section are 35 cents perw,ord, each insertion, and mustbe accompanied by cash toinsure publication.

Each initial or abbreviationcounts a full word.

Minimum classified charge $3.00.

For ads on which replies aresent to us for forwarding (blindads), there is an additionalcharge of $3.00 per insertion tocover department number, pro-cessing of replies, and mailingcosts.

Classified columns are not opento advertising of any productsregularly produced by manufac-turers unless used and nolonger owned by the manufac-turer or a distributor.

For SaleTUNER SUB ONLY $19.95, wired, tested, com-plete with batteries and ready to use on tube ortransistor sets. This unit is without knobs orcabinet but very compact with no wires orcontrols dangling. Easy to use, simply hook set'scoax to sub and view picture (instructions pro-vided). Only $19.95, we pay the shipping. This isnot a gimmick. If not completely satisfied, returnwithin 10 days for full refund. TEXAS TUNERSERVICE, 4210 N.E. 28th Street, Fort Worth,Texas 76117. Phone (817) 834-8201. 1-78 3t

COMPLETE COLOR PICTURE tube rebuildingsetup. Lathe, oven, glassblowing equipment. Topcondition. Contact M. Scholz, Box 271, ChristinaLake/B.C. Canada, Tel. 604-447-9500. 2-78-2t

advertisers/1m

REPLACEMENT COLOR YOKES -DEALERS ONLY.Zenith 95-2501-2532-2638-2667-S-89633 etc 16.95,Magnavox 361380-1 18.95, Sylvania, GE etc. 14.95to 19.95. Request for price list on yourLetterhead. David Sims Enterprises, Inc., 665Jericho Turnpike, Huntington Station, N.Y.11746. 12-76-tf

SEEKING ORIGINAL JAPANESE TRANSISTORS,IC's FET AND DIODES FOR CB AND STEREOREPAIR? See our large ad in this issue for listingof parts and prices. Write or call for our completelist and compare prices. FUJI-SVEA ENTER-PRISE, Dept. ES, P.O. Box 30325, Cincinnati, OH45240 (513) 874-0220. 2-78-21

BIK 1077 B TV Analyst $250.000 HeathkitPost-Marker/Sweep Gen. $100.00. Allen Rose,650 Daphne, Broomfield, Co. 80020. 3-78-1t

TV & RADIO TUBES 36c EA!! Free color catalog.Cornell, 4221 University, San Diego, California92105. 8-76-tf

Business OpportunitySAVE HUNDREDS OF DOLLARS on high quality,dependable, American Made, MATV Head -Ends,V/V, U/V Converters, Camera Modulators, atfactory -direct prices. Send $5.00 (or your MATVInstallers Letterhead). "Information", Box 809,Boynton Beach, Fla. 33435. 1-78 51

TELEVISION SALES SERVICE established twentyyears major brands mid Ohio growing community.Modern store, central location, gross exceeds$100,000. Owner retiring. Principals Only. Elec-tronic Servicing, Dept. 515. P.O. Box 12901,Overland Park, Kansas 66212 3-78-2t

Education -InstructionREPAIR TV TUNERS-High Earnings. CompleteCourse Details. 12 Repair Tricks. Many Plans.Two Lessons, all for $2 Refundable FrankBocek, Box 3236 Enterprise. Redding. Calif96001 8-76-11

FCC 1st -2nd -3rd questions and answers. "Expla-nations" compiled from technical schools, col-leges and avionics companies. $11.00. S. Mager,Box 26151, Los Angeles, California 90026.

3-78-1t

American TechnologyCorp. 11

B&K Precision, DynascanCorp. Inside Back Cover

Dynascan Corp., B&KPrecision _Inside Back Cover

Electron Tubes Int'l 2

Fuji-Svea Enterprise 51

Gamit Enterprises, Inc. 49

General Electric Co.,Tube Div. 3

Hickok ElectricalInstruments 23

NATESA 50

NESDA 49

Non -Linear Systems 50North American Electronics ..7Oelrich Publications 49

Oneida Electronic Mfg. Inc. ..8Optima Electronics 39PTS Electronics

Inc Inside Front Cover, 1RCA Distributor and Special

Products 12-13Sperry Tech, Inc 50Zenith Radio

Corp. ....19, 27, Back Cover

MAKE PC BOARDS. Step-by-step "how-to"manual with build -it -yourself equipment plans,charts, and illustrations. For Polyez and Film -Chemical processes. $4.98 plus 50 cents P&H.Century American Instruments, Dept. 414, Box1014, Placentia, CA 92670. 3-78-1t

WantedSTART ELECTRONIC FACTORY IN YOUR HOME.GET STARTED IN YOUR SPARE TIME. ONE MANOPERATION. EXPECT BIG PROFITS. EXPERI-ENCE NOT NECESSARY. PRACTICALLY NOINVESTMENT. WRITE FOR FREE LITTERATURETELLING HOW. ELECTRONIC DEVELOPMENTLAB, DEPT. A, BOX 1535, PINELLAS PARK, FL33565. 8-77-tf

Help WantedOUTSIDE SERVICE TECHNICIANS. Paying topwages for best qualified men. Qualifications forposition: total honesty, industrious, ten or moreyears direct television experience, non-drinker, non-smoker, must be able to workwithout supervision. Present employees grossingover $20,000 yearly. Send resume to AmericanTelevision Service, 1032 South State, Orem, Utah84057. 2-78-4t

TUNER TECHNICIAN NEEDED with ability tomanage an established tuner and module servicein the Dallas/Fort Worth area. Wages is $7.00 perhour. Recent experience at one of the major tunerservices required. Texas Tuner Service, 4210 N.E.28th Street, Fort Worth, Texas 817/834-8201.

3-78-1t

ELECTRONIC TECHNICIANS-MOTOROLA, lead-er in two-way radio communication, presentlyhas openings throughout the U.S. for techniciansand supervisors experienced in the installationand maintenance of communications systems(two-way, paging, microwave and CCTV). Ifinterested in good salary and excellent fringebenefits send your resume and geographicalpreference to: BOB CLENDENIN, MOTOROLA,COMMUNICATIONS & ELECTRONICS, INC., 1821N. Office Square, Room 200C, Schaumburg, IL.60196. Equal employment opportunity/affirmativeaction employer. 3-78-3t

RegionalAdvertising Sales Offices

INDIANAPOLIS, INDIANA 46280Roy Henry, 2469 E. 98th St.;Phone: (317) 846-7026

GREENLAWN, NEW YORK 11740Chuck Homer, P.O. Box 175;Phone: (516) 757-7863

MOUNTAIN VIEW, CALIFORNIA 94043Dennis Triola, 2680 BayshoreFrontage Road, Room 102;Phone: (415) 961-0378

LONDON, W.C. 2, ENGLANDJohn Ashcroft & Co., 12 Bear Street,Leicester Square; Phone: 930-0525

1171 VC-BADHOIVEDORP,HOLLANDJohn Ashcroft 8, Co., John J.Lucassen, Mgr., Sloterweg 303;Phone: 2968-6226

TOKYO 105, JAPANInternational Media Representatives,Ltd., 2-29, Toranomon 1-chome,Minato-ku; Phone: 502-0656


Test semiconductorswithout testing your patience.The real value of using a semiconductor testershould be time savings. B&K-PRECISION semi-conductor testers are designed for maximumspeed and reliability to save you more time thanany other testers.

B&K-PRECISION semiconductor testers areproved as highly cost effective answers to

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1530 Semtconducto- TesterMeasures unity gain (Yr)o 1500MHz instantly

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DarlinOons in -circuit or out Works In -circuit where

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Model 510 Transistor Tester Completely portable

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Model 50IACurve -racer

DisplaYc haractensticr cu-ves on rr ost anys:ope

Clmclete with uni reDynaf ex probe

The B&K-PRECISION Model 530 is one of the mostversatile semiconductor testers available and canactually perform more tests on more devices than anyinstrument in its price class. Features include: Exclu-sive patented fr measurement circuit...Non-destruc-tive breakdown voltage testing...Automatic lead andpolarity identification, in- or out -of circuit... Measure-ment of beta and gm...Aural and visual test indica-tions...Testing of new power FET's. CSA listed. $310

For value, the Model 520B industrial semiconductortester is tough to beat. Dynapea101 circuitry with high/low drive allows the 520B to work in -circuit whereothers won't...A complete test takes about 9 seconds...Identifies all leads of transistors and SCR's andpolarity... CSA-listed version available... 'Gooddevice" indicated visually and aurally. $175

At only $97, the Model 510 offers Dynapeak testmethod reliability with pocket-size portability... LEDtest result indicators...Tests all types of transistors,FET's and SCR's...Digital stability never needs cali-bration...Complete with case and leads. $97

When applications demand analysis of the charac-teristic curves of semiconductor devices, the B&K-PRECISION Model 501A is the cost-effective answer...Displays characteristc curves for all semiconduc-tor devices on most any scope...Non-destructivebreakdown voltage tests...Simulates actual operat-ing conditions...Internal calibration source...Cur-rent limiting protects device under test. $198

Start testing semiconductors faster now. See yourlocal distributor for immediate delivery.

DYNASCANCORPORATION

6460 W Cortland Avenue, Chicago, IL 60635 312/889-9087In Canada: Atlas Electronics, Ontario International Sales: Empire Exporters, Inc., 270 Newtown Road, Plainview, LI., NY 11803


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IINI:Enound Repair...An up front discussion on tuner repair and module rebuilding. TV service...

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Transcript of IINI:Enound Repair...An up front discussion on tuner repair and module rebuilding. TV service...