SYLVANIA HELPS...(.courtesy of RCA), a trip to Nogales, Mexico courtesy of Hiser Publications and a...

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SYLVANIA HELPSSOLVE GE AND

RCA'S PROBLEMS.

No one knows better thanSylvania that the show mustgo on. So when a faulty semi-conductor in any brand ofhome entertainment productturns into a showstopper, it'sSylvania to the rescue. OurECG" semiconductor guideis the most used, and useful,guide in the industry. It makesit easy to replace any ailingperformer with an ECG semi-conductor that will get theshow back on the road.

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When it comes to replace-ment parts the right place tocome is Sylvan a Your Sylvaniadistributor carries a completeline of ECG' semiconductors,picture tubes, receiving tubes,and test equipment designedto make any braid work likeit's brand new.

Sylvania. The easy way toget even the hardest part.

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ECG is a registered trademark of GTE Sylvania.

Circle (1) on Reply Card

Electronic Servicing

Editorial, advertising and circulation corre-spondence should be addressed to P.O.Box 12901, Overland Park, KS 66212 (a

suburb of Kansas City, MO); (913) 888-4664.

EDITORIALBill Rhodes, Editorial DirectorCarl Babcoke, EditorCindy Nelson, Managing EditorJoan Jackson, Editorial Assistant

ARTDudley Rose, Art DirectorLinda Franzblau, Graphic Designer

CIRCULATIONJohn C. Arnst, DirectorEvelyn Rogers, Manager

ADMINISTRATIONGeorge H. Seferovich, PresidentGeorge Laughead, Publisher

ADVERTISINGCameron Bishop, Marketing DirectorJim Reilly, National Sales ManagerLauri Gash, Production

Regional advertising sales offices listednear Advertiser's Index.

Member.5: -ABP American Business Press

Member,Audit Bureauof Circulation

ELECTRONIC SERVICING CUSPS 462-050)(with which is combined PF Reporter) ispublished monthly by Intertec PublishingCorp., 9221 Quivira Road, Overland Park,KS 66212. Controlled Circulation Postagepaid at Shawnee Mission, KS 66201. SendForm 3579 to P.O. Box 12901, OverlandPark, KS 66212.

ELECTRONIC SERVICING is edited fortechnicians who repair home -entertainmentelectronic equipment (such as TV, radio,tape, stereo and record players) and forindustrial technicians who repair defectiveproduction -line merchandise, test equip-ment, or industrial controls in factories.

Subscription prices to qualified sub-scribers: 1 year-$10, 2 years-$16, 3

years-$20, in the USA and its posses-sions. All other foreign countries: 1

year-$13, 2 years-$22. Subscriptionprices to all others: 1 year-$25, 2

years-$50, in the USA and its posses-sions. All other foreign countries: 1

year-$34, 2 years-$68. Single copy price$2.25; back copies $3.00. Adjustmentnecessitated by subscription termination tosingle copy rate. Allow 6 to 8 weeksdelivery for change of address. Allow 6 to 8weeks for new subscriptions.

INTERTEC PUBLISHING CORP

Terminating loadresistors fromDielectricDielectric, the leader in supplying the communi-cations industry with RF measuring instrumenta-tion, has a wide selection of Terminating Load

Resistors. From a 5W dry loadto a 50KW heat exchanger typeload, Dielectric has a dummyload that meets your power andfrequency requirements. Low power dry loadsare available up to 150 Watts. Liquid/Air loadsup to 10,000 watts and high power loads -either direct water-cooled or with heat

exchanger - up to 50,000 watts. All loadshave a minimum VSWR specification of 1.1:1(or better) over their rated frequency ranges.

RF Instrumentsfor ProfessionalsFor the name of your local distributor, call Toll Free 800-341-9678.A limited number of distributor locations are currently available: inquiries welcomed.

DIELECTRIC COMMUNICATIONSA UNIT OF GENERAL SIGNALRAYMOND. MAINE 04071 TEL 207-655-4555 800-341-9678


In August

Electronic ServicingA unique method of curing unwantedRF carrier interference, electronicmedical equipment repairs, plus moreon the microprocessor series.Waveforms part 3 shows replacementsin scan -rectified power supplies.Plus, the introductionof Electronic Servicing'snew MRO industrial electronicservicing section.

July 1979 Electronic Servicing 1

July, 1979 Volume 29, No. 7 Electronic Servicing®

1 A second look at waveforms, Part 2Gill Grieshaber

Waveforms prove that an old vertical -sweep theory iswrong. Presentations are made of waveform analysisand servicing tips.

2t Digital numbering systemsJack Webster

Digital technicians must know these basic facts aboutfour different numbering systems that are used bymicroprocessors.

Highlights of 1980 productsElectronic Servicing staff

Summaries are given of the 1980 television, audio andvideocassette products from several manufacturers.

Techniques for repairing intermittentsRobert L. Goodman

These examples and technical tips can help solve inter-mittent problems.

41., A meter that liedWayne Lemons

A VOM appeared to read an ac voltage either correctlyor as zero, but both readings were wrong.

Departments 3 Electronic Scanner4 Troubleshooting Tips

11 Symcure12 Puzzle

13 People in the News41 Test Equipment42 New Products43 Catalogs & Literature

About the cover The graphic design of vertical -sweep waveforms is byLinda Franzblau with photography by Carl Babcoke.

Copyright, 1979, by intertec Publishing Corporation. All rights reserved. Material may notbe reproduced or photocopied in any form without written permission of publisher

2 Electronic Servicing July 1979

0

° riifi a rJ snews of the industry

First annual convention of the Electronics Technicians Association -International (ETA -I) isscheduled for August 3 through 5 at the Bingeman Park Convention Center in Kitchener, Ontario,Canada. Technical seminars, leadership sessions, business -management school, certificationworkshops, business meeting and election of officers are part of the activities. For moreinformation, contact: ETA -I, Dept. ES. 7046 Doris Drive, Indianapolis, IN 46224. The phonenumber is (317) 241-7763.

The Marriott Hotel in Tucson, AZ was chosen for the national annual convention of the NationalElectronic Service Dealers Association (NESDA) and the International Society of CertifiedElectronic Technicians (ISCET), and the state convention of the Arizona State ElectronicsAssociation August 13 through 18. In addition to association business sessions and the election ofofficers, other items on the agenda include business management and new technology schools, theElectronics Roundup trade show, CET tests, manufacturer/service forum, technical seminars, Hallof Fame awards and council meetings. Recreational activities include a day in Old Tucson(.courtesy of RCA), a trip to Nogales, Mexico courtesy of Hiser Publications and a golf tourney.For information write to: NESDA, Dept. ES, 2708 West Berry Street, Fort Worth, TX 76109, phonenumber, (817) 921-9061.

National Association of Television & Electronic Servicers of America [NATESA] has scheduled itsnational convention at the Carson Inn of Nordic Hills. Itasca, IL August 23 through 26. Manyevents are scheduled in addition to the association business. These include profit -producingseminars, contacts with key industry people, a certification test, technology trends and reports onindustry problems and solutions. Carson Inn has a large golf course, indoor swimming and manyother recreational activities. The NATESA awards banquet with floor show is one of thehighlights. Write to NATESA at 5809 South Troy, Dept. ES, Chicago, IL 60629, or call (312)476-6363.

US factory sales of electronic equipment, systems and components totalled $64.9 billion in 1978,representing an increase of nearly 150/0 over the previous year, according to the 1979 ElectronicMarket Data Book, released by the Electronic Industries Association. The other major electronicindustries also showed growth in 1978 with sales of consumer electronics increasing nearly 150/0,electronic components 140/o and communications equipment 120/0. Employment in the electronicindustries grew by 90% in 1978, to more than 1.3 million workers. This growth rate was almostdouble the increase in overall US employment.

The 1979 International Summer Consumer Electronics Show, June 3-6, featured a record 938exhibitors and established a new high attendance of 60,824. The CES is sponsored and producedby the Electronic Industries Association Consumer Electronics Group. The CES Design andEngineering Exhibition showcased nearly 100 products selected by a panel of judges as among themost innovative of the year. Additional CES special exhibits included the CES Retail ServicesCenter where retailers met with finance companies, store layout experts, freight forwarding andother retailer service suppliers.


troubIesilootinoÍtJ

Insufficient heightMagnavox T987(Photofact 1411-2)

According to the customer, thetrouble started with a small lineacross the top of the screen andincreased until the picture only hadabout 1/3 height. The linearity wasstretched at the top, and thelinearity control adjustment hadlittle effect.

All transistors on the verticalmodule checked normal, as did theoutput transistors. However, dcvoltages at the output transistorswere wrong.

Because many electrolytics hadcaused trouble lately, I decided tocheck those in the vertical circuit.

M201 VERTICAL OSC- DRIVE MODULE

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Paralleling C203 made no change,but a new 20 14F across C204restored the height. After thecapacitor was replaced and theheight and linearity controls ad-

justed, the vertical sweep wasentirely normal.

Richard SerranoMadera, CA

Tinted rasterRCA CTC38XA(Photofact 1092-3)

When the color control wasturned down completely to removethe color, the raster had a greentint on one side and a purple tinton the other half. Further, whenthe color killer was rotated CCW,the unwanted color was gone. Ofcourse, no color was possible theneven after the color control wasturned up again.

The problem seemed to be on thechroma circuit board, and that areawas tested first. But after severalhours of work, no defects had beenfound.

Finally, I noticed some slightbending and weaving that movedup through the picture. This sug-gested filter problems, and peak -to -peak scope readings were taken atall can filters. C2 and C3 checkedalright, but the C3 ripple was toohigh. Some dried electrolyte wasnoticed around the terminal. Al-though I didn't believe the badfilter could be responsible for the

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color shading, I decided to replaceit. To my surprise, the shading wasgone from the raster.

George M. Marechek, Jr.Cheverly, MD

Editor's Note: The CTC38 colorkiller biases all three -Y amplifiersto cut off. They receive voltagefrom C3 and the +375-V supply,and thus amplified the hum whilethey conducted. However, whenthey were cut off, the hum was notamplified and could not reach thepicture tube.


Intermittent oscillatorRCA CTC38(Photofact 1092-2)

Only the horizontal -output tubehad been bad. This was the easiestrepair of the day (or so I thought).No complaint or comments were onthe repair order. But then a lack ofraster was obvious.

Next morning the bench powerwas on only a couple of minutesbefore I realized the easy repair jobwas not showing a picture. Also,the smell of a hot tube wasnoticeable. By the time I could shutoff the TV, the output tube wasruined. I replaced the output tube,watching carefully for a red plate orany sign of trouble. Nothing ap-peared but a normal picture.

Jarring the horizontal -oscillatorcomponents or heating and coolingthem didn't affect the operation.All day it played.

Before the power was applied tothis TV the next day, I connected ascope to the output grid andwatched for a red tube as the powercord was plugged in. The scopeshowed no grid drive and the ouputplate began to glow redly. Therewas no output from the horizontaloscillator.

To prevent the destruction ofmore output tubes, I connected thescope with test leads to the outputgrid with the tube removed andthen turned the power on and off at

HORIZ OSC

s 6F07/6CG7

HORIZHOLD

35K

intervals. Only one try in twentyshowed no horizontal drive. I

removed the oscillator tube (outputstill was out of socket) and pluggedit into the socket at intervals. Thisprocedure caused a loss of oscilla-tion every time. Finally, a carefulcooling of one component at a time

identified the 390 pF grid capacitor(C111) as the culprit. It was a discnegative temperature coefficient ce-ramic that showed a crack aroundthe edge,solved the

and a new replacementintermittent problem.

Roger ReddenBeaver, WV

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ifli°ixcbanueThere is no charge for a listing in Reader's Exchange, butwe reserve the right to edit all copy. If you can help with

a request, write directly to the reader, not to ElectronicServicing.

Needed: Good used 490BLB22 color picture tube and19VAR B&W picture tube. For sale or trade:510CTB22 color and old B&W 24CP/TP/QP/XP picturetubes. Mike's Repair Services, P.O. Box 217,Aberdeen Proving Grounds, MD 21005.

Needed: One new 16BXP4 picture tube. For sale ortrade: model 465 B&K-Precision CRT tester andVoltOhmyst Senior RCA VTVM. Both in good condition.W. Hitchcock, Route #3, Birch Tree, MO.

Needed: Schematic and service data for a model 52Crosley radio and a Clough-Brengle model 225 tubetester. Also, dates of manufacture? Raymond Friend,236 West Pearl, Butler, PA 16001.

For Sale: Complete set of Rider's TV manuals withindex. Also, Rider's radio manuals less one volume,test equipment, and old tubes. Westfield Radio, P.O.Box 367, Westfield NJ 07090.

For Sale: New Sencore SM158 sweep generator, $195;Sencore BE156 power supply, $19; and Heath IG28,$70. All with leads and manuals. Don Brentlinger,4822 Sparks Avenue, San Diego, CA 92110.

Needed: Used FM 2 -way -radio course by MTI. JohnWebb, Route 2, Gibson, GA 30810.

For Sale: Heathkit model I0-12 scope with leads andmanual, like new, $75; and 300 seldom -used tubes, $1each plus postage. Send SASE for list. J. R. Blundin,151 West 3rd, Mt. Carmel, PA 17851.

For Sale: B&K-Precision model 415 sweep/marker,$375; B&K 501 curve tracer, $125; Leader LB -501scope, $150; Leader FET VOM, $45. All B&K in topcondition; all prices plus shipping. Milton Obuch, 1308N. 4th Sayre, OK 73662.

Needed: Manual and schematic for model ST55MXPaco FM -stereo receiver. Will buy, or copy andreturn. Paul Ciarelli, 17 Pebble Lane, Levittown, NY11756.

For Sale: Lampkin 107C service monitor, like new,$2850; RCA WT -524 transistor checker, $120; B&K-Precision 1474 30 -MHz dual -trace scope with probes,$700; Heathkit IB-1103 frequency counter, $225;Betamax jig kit, $225; Panosonic jig kit, $100; EICOflyback tester, $40; Heathkit IG-5237 stereo generator,$70; Heathkit SG -18 audio generator, $65; Heathkit1D-5252 audio load, $25; EKTAL 220 viewer, $90; 3Mmodel 149 copier, $70. Manning Jeter, 1029 EastFairview Avenue, Montgomery, AL 36106.

Needed: UHF sweep generator covering 470 MHz to600 MHz. John Morgan, 3008 Ozark Road, Chattanoo-ga, TN 37415.

For Sale: Lampkin Micrometer frequency meter type105-B, $150. Arnold Kading, Box 285, Hackensack,MN 56452.

Needed: Tube caddies and tube stock. Send pricesand tube numbers. Mark McDonald, 2-1610 East CliffDrive #12, Santa Cruz, CA 95062.

For Sale or Trade: Extra Rider's manuals andtextbooks for the 1940s and earlier. LawrenceBeitman, Box 46, Highland Park, IL 60035.

Needed: Complete tuner -control panel with face plateand knobs (mounted on front of cabinet) for modelGP634L RCA console TV. Bob Vellines, Jr., 1228 EastRidge Road, Gary, IN 46409.

Needed: Service and parts manuals for model 636Jackson tube checker and EICO model 955 capacitortester. Also, want Rider's radio manuals volumes 1through 5 (unabridged) and 19 through 23; have otherRider's to sell or trade. Stan Lopes, 1201 MonumentBoulevard #74, Concord, CA 94520.

Needed: Schematic for a model 125565 old Zenithradio. It has 12 tubes, 2 short-wave bands andbroadcast band. Holme Radio, 602 North 11th Avenue,Lake Worth, FL 33460.

For Sale: Kenwood combined SM-220 station monitorand BS -8 pan display, new in original box, $370; alsoa More -Gain multiband 10/80 -meter dipole antenna,$45. William Shevtchuk, One Lois Lane, Clifton, NJ07014.

Needed: Good used triggered dual -trace scope, suchas Telequipment, Sencore, etc. John Martin, 105Fernwood Avenue, Weirton, WV 26062.

Needed: Schematic and service data for a model12-8300 Webcor stereo system. Or need presentaddress for Webcor. Will buy data, or copy andreturn. Real Lausier, 30 River View, Madawaska, ME04756.

Needed: Photofact 78-7 for a GE -800 TV. AlbertPecaites, 4048 Wesxt 161st, Cleveland, OH 44135.

Needed: Receiving -tube adapters for model 658Jackson deluxe tube tester. Bob's TV, 1822 Sun Valley,Jefferson City, MO 65101.

Needed: Schematic and parts data for a Hy -Gain 8model 3108. Will buy, or copy and return. AllenFryou, 3735 Fairmont Drive, New Orleans, LA 70122.

For Sale: Philco 9 -inch meter for panel mounting, withmanual, $30; Rider's TV manuals volumes 1 through26, with index, $130; Measurement Labs model 78B


signal generator, $35; Sylvania model 500 TV sweepgenerator, new in original carton, $70; 7 -inch Ram -88circular saw, $20; Black & Decker 1/2 -inch drill withgeared drive, $20. M. Seligsohm, 1455 55th Street,Brooklyn, NY 11219.

Needed: Operating manuals for Hickok Traceometermodel 156, Sprague Telomike model TO -4, andMeissner signal tracer. James Humphrey, 1006 East28, Los Angeles, CA 90011.

For Sale: Triplett 601 FET VOM, $100; Hewlett-Pack-ard 330D distortion analyzer, $225; H -P 200CDwide -range audio oscillator, $125; H -P 410B VTVM,$125; H -P 5382A 225 -MHz frequency counter, $325;Monsanto 1106A counter plug-in unit, $120; Tektronixplug -ins "T" $175, "82" $325, "CA" $125, "H" $75,"N" $125; Tektronix P6008 probes, four for $60 each;Ballantine 310A ac VTVM, $60; Unico 202 explosive -vapor detector, $75. All units are in good -to -excellentcondition. Ronald Zimmerman, 10836 4 -Mile Road,Franksville, WI 53126.

Needed: AM/FM/OFF function switch, part 2006441-61 for model 40L43-19 Arvin AM/FM/cassette receiv-er. Kenneth Stuckwisch, RR #4, Seymour, IN 47274.

Needed: Schematic for a G110 Electronic MusicCorporation (EMC) guitar amplifier. Gordon's Electron-ique, 3760 Provost, Lachine, Quebec H8T 1L7.

Needed: Frequency counter with minimum of 6 digitsand 30 MHz. Also, need grid -dip meter, such as Heathor EICO. State price and condition. Caswell Davis, Jr.,601 Delmar Apt. 2, San Antonio, TX 78210.

For Sale: Model 567 EICO multimeter with leads andmanual, good working order and calibrated, $25;Heathkit IM -1210 21/2 -digit (Bell & Howell) digitalmultimeter with probes and manual, $30; Sanwamodel V-50 multimeter, good working order, $10. Allprices plus shipping. Donald Young, 1037 South ParkDrive, Brookfield, OH 44403.

Needed: Service data for model 2020P Shell Electron-ics stereo amplifier, model FM -15 Transitronics FMtuner. Will buy, or copy and return. T. Earl, 1317Kingston Drive, Yukon, OK 73099.

For Sale: B&K-Precision 1040 Servicemaster and 1640power supply, and Hickok 380X frequency counter. CBequipment is three years old and in excellentcondition. Write for price. LeRoy Barnes, 229 Watson,Camden, TN 38320.

For Sale: Used electronic courses. NRI completeaudio/TV course with 48 lesson texts, 10 referencetexts but no training kits; Heathkit EE -3102 AC/elec-tronics course with EE -3103 semiconductor devices,EE -3104 electronic circuits, ET -3100 basic trainer and

MASTERheat gun

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Heating shrink tubing is just one of many jobs the MasterFlameless Heat Gun performs in electronic assembly. It'sthe perfect source of fast, portable heat for drying com-ponents, heat -checking circuitry, softening plastics andadhesives, melting solder, etc. Industrial quality for pro-duction line duty. Eight models: 200°F to 1000°F, 120Vor 230V. UL listed - CSA certified. Base plate rotates90° for convenient benchtop use. Special applicationattachments available.

For FREE product bulletin from theoriginators of heavy duty heat guns,contact your distributor, or call orwrite:

In Canada. contact Martin IndustrialSales. Ltd. 4445 Harvester Road.Burlington Ontario L7L 2X1

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with all parts; Heathkit EE -3401 microprocessorcourse, ET -3400 microcomputer trainer, partial EE -3201 digital techniques with parts but no ET -3200trainer. Offered only for each complete course series;best offer. Red Bull Electronics, 4807 Fifteenth AvenueS.E.. Lacy, WA 98503.

Needed: Complete exact tuner replacement for modelPL17F32B Admiral portable TV. VHF tuner number is94E163 -1D, using 2CY5 and 5CGB8. John Lefko, 18 DeliCourt, Fairfield, CA 94533.

Needed: Model 1077B Analyst with manual andaccessories. Clarence Gillow, 608 Black Drive,Prescott, AZ 86301.

For Sale: Heathkit LO -101 vectorscope; HeathkitIT -7400 digital IC tester; Conar 255 triggered scopewith 3 probes; Conar 214 transistor tester; Conar 311R/C tester; Conar 202 frequency counter; Conar 212TVOM with HV probe; EICO 270 DMM with acadapter. All in good operating condition for 500/o oforiginal kit cost. Red Bull Electronics, P.O. Box 2531,Olympia, WA 98507.

For Sale: Heathkit square -wave generator, $15. D.Pollock, 178 Pinckney Road, Little Silver, NJ 07739.

Needed: Power transformer for model M-1537 Philcostereo; part number 325-0127-1. W. B. Jones, P.O. Box354, Carnesville, GA 30521.

For Sale: Heathkit model 8T-5230 CRT tester/rejuve-nator, hardly used, $115; Heathkit DVM modelIM -2202, $125; Weston model 1250 frequency counterto 55 MHz, $105; RCA model WA -504B audiogenerator, $80; Photofacts 1 through 800 in cabinets,$350. Ash Lakhiani, 48 Route 10, East Hanover, NJ07936.

Needed: Original 2SA290, 2SÁ289 and 2SA288transistors for a VHF model TV6U Singer TV tuner, oraddress where they can be purchased. TheodoreAnderson, 435 E. 105 Street, New York, NY 10029.

For Sale: Rider's early volume 1, 1919 to 1927, $15;complete index for Rider's volumes 1 to 23, 270 pages,$15; RCA 1922-1932 service data, 200 pages, $15; andRider's radio volumes 10, 11, 12 and 13, $15 each.Antique Radio Shop, 3403 Broadway, Long Beach, CA90803.

Needed: Information where the field coil of an antiqueradio can be rewound. C. S. Wood, 50 Brixham Road,Eliot, NE 03903.

For Sale: Model 510 B&K-Precision transistor testerwith probes and manual, almost new, $75; 34 issues ofElectronic World to December, 1971, $10 plus shippingcosts. Aurie Antilla, 4066 Mt. Everest Boulevard, SanDiego, CA 92111.

For Sale: A 25 -year accumulation of tubes, parts, PFReporter and Electronic Servicing. Send self-addressed envelope with list of needs. C. E. CombsTV, Route 2 Box 184-C, Crawfordville, GA 30831.

For Sale: All issues of PF Reporter/ElectronicServicing from 1951, in good condition, best offer plus

shipping; also, other publications and older Photo -facts; many radio and TV tubes. Write for details.Frank Zablocki, Box 531 Ferry Road, North Haven,Sag Harbor, NY 11963.

Needed: Copy of AR -96 auto -radio Photofact (now outof print): will buy. C. G. Howard, 70 Richards Road,Columbus, OH 43214.

For Sale: Radio Electronics from 1946 to 1974; Service1946 to 1958; Electronic Technician from 1955 to 1977(no schematics). You pay shipping; make offer. JosephKouril, 71 Morton, Brentwood, NY 11717.

Needed: One model 375 B&K VTVM, working or not.State price and condition. Charles Ruffner, 4032 PascoGrande, Tucson, AZ 85711.

For Sale: 500 old -type tubes in original boxes,reasonable price. Send for list of tube numbers.Delman TV, 651 East Park Avenue, Long Beach, NY11561.

Needed: Rubber drive rim for Presto 16 -inch tran-scription turntable. Grant Canfield, 1600 MokuluaDrive, Kailua, HI 96734.

For Sale: Model 500 Sylvania TV sweep generator,new in carton, $60; Rider's TV manuals, volumes 1through 26, $120; Rider's Radio manuals, volumes 16and 17, $10 each; Philco VTVM for panel mount, with9 inch meter and manual, $25; model 78B Measure-ment Lab signal generator, $25; assorted text books.Send for list. Prices do not include shipping. M.Seligsohn, 1455 55th Street, Brooklyn, NY 11219.

For Sale or Trade: Miscellaneous antique radiosincluding National Radio & TV model Apex 36; alsosome old tubes. Need Rider's volume 23 and any indexfor Rider's 1-15 or 16-23. Barry Evans, 11115 East 50thStreet, Kansas City, MO 64133.

Needed: Schematic or specs of a B+ droppingresistor for model MS6-FM AM/FM intercom. PaulWojcik, 207 North 18th, Barrington, IL 60010.

Needed: Model 1070 B&K-Precision Dyna-sweep cir-cuit analyzer. J. D. McKissack, 1740 23rd AvenueNorth, Nashville, TN 37208.

Trade: Will trade a model 415 B&K-Precisionsweep/marker generator for a B&K model 1077B TVAnalyst in good condition. Virgil Collins, Sam's TV,Mammoth Street at Beatrice, Thayer, MO 65791.

For Sale: Heath SG -18A sine/square generator,factory wired; model 415 B&K-Precision sweep/mark-er generator; Sencore FE -21 FET meter; SpragueTO -6A Telohmike capacitor analyzer; Sencore PR -47UHF prescaler and NE -206 noise eliminator; B&K-Pre-cision model 747B tube tester. All in excellentcondition and operation. Sell any or all for best offers.Christian TV & Audio, 6916 Silver Star Road, Orlando,FL 32808.

For Sale: PF Reporter from November 1959 to August1967 (less 1965) plus a few later issues. Send stampedself-addressed envelope for price and details. Cheri'sTV, 1300 15th Street, Wyandotte, MI 48192.


ícure Symptoms and curescompiled from field reportsof recurring troubles

Chassis-Magnavox T995PHOTOFACT-1815-1

VIDEO AMP

Q4

R11

360

R14

33 R14

360

OPEN =

SHARP

Symptom-Good sound and bright raster withoutmuch videoCure-Check R14 sharpness control, and replace it ifopen


VERT OUTPUT TOQ8 VERT

YOKE

SHORTED

TURNS

+ 30V

Symptom-Foldover near center of vertical sweepCure-L1 vertical choke might have shorted turns;replace it

Chassis-Magnavox T995 with Touch -TunePHOTOFACT-1815-1

AGC

UHF

TUNER

TUNING

VOLTAGE

BAD

TUNERVHF

TUNER

Symptom-VHF stations drift slowly off channelCure-Check for tuning voltage leakage inside UHFtuner


INTERMITTENT

R11

RIG

90

TO

CONVERGE

COIL

Symptom-Intermittent convergenceCure-Replace diode D8 on convergence panel; alsocheck diodes D5 and D6 on the mother panel.


II

IIII

32

I

IIIIIII

B PANEL

BURNING

Q1 ABL

Symptom-No HV and R39 on B panel is burningCure-Check regulator transistor, HV tripler andflyback; Replace any that are defective


T1BFLYBACK I

+132V

Symptom-Dark picture but good high voltage, andvoltage at TP30 is lowCure-Replace the flyback as a test


1 @©Qj©ui©by Edmund A. Braun

'Round and 'round she goes, where you are stopped, nobody knows! That's thewhole shebang on this Pinwheel Puzzle based on Electronics. The last letter ofeach word is the first letter of the next word. Each correct answer is worth 4points, a perfect score is 116. It should prove quite easy except perhaps forsomeone who thinks "sensor" is someone who eliminates the X-rated words, orbelieves "vacuum" is where the Pope lives! So pick up your pencil and get ahigh score. Ready? Then GO!!

1 Starting and stopping periodically.2 Metallic element used in high -reliability capacitors.3 Machines that convert electric energy into mechanical

energy. 16

4 Set of plates in a variable capacitor that remain in afixed position.

5 In TV, 3 circuit generally using a diode tube which 18

automatically supplies bias voltage to picture tubegrid. 19

6 In a circle, the angle included within an arc equal io 20

radius of the circle. 21

7 Pertaining to a disc used for scanning areas of an 22image in correct sequence for a mechanical TV 23

system. 24

8 Unit of magnetic flux.9 Unmodulated pattern on a kinescope face. 25

10 This uses a pawl to prevent reversal of motion. 2611 Converts energy from one form to another.12 Opposition offered by magnetic substance to magnetic 27

flux. 2813 Decorative metal wood, or other material around

knobs, etc. 29

1415

17

Radio or TV program dealing w.th current events.An abnormal connection of relatively low resistancebetween two points of a circuit.Non -vacuum electronic device similar in use to anelectron tube.Converted from ac to dc.Used to hold indexed rotary switches firmly inselected position.Used to adjust receivers to frequency of sender.Sign or letter used to designate something else.Authority granted by the FCC for broadcastingCapacity for performing work.Coils on a picture tube.Pertaining to a closed curve in the form of asymmetrical oval.An optical device which focuses light by refraction.Thin metal vane which has been perforated with anappropriate wave pattern.Muffling or deadening a sound.Material introduced into a vacuum tube duringmanufacture for greater evacuation.The movable plates of a variable capacitor.

The easiest part of this puzzle is to find the sólution on page 41.


0 0 I in the news

Terry Banks, general manager of PTS-Indianapolis has been named PTSElectronics' "Man of the Month." JackCraig, right, PTS regional manager,presented the award to Banks who hasbeen with the firm for six years.

Recent Developments in Arc Sup-pression for Picture Tubes, co-auth-ored by James W. Schwartz andMark Fogelson of Zenith RadioCorporation, has been selected thebest paper of the 1978 Chicago FallConference on Consumer Electron-ics. The paper reviews past devel-opments in picture tube arc sup-pression systems and describes anew system, invented and patentedby James W. Schwartz, et al.

William L. Thomas, Gary Sgrig-noli and Walter S. Ciciora, also ofZenith, took second place honors fortheir paper, A Tutorial on Ghost.Cancelling in Television Systems.

George A. Scherer has beenpromoted to chief engineer, RFProducts at Blonder -Tongue Labora-tories. Scherer joined the companyin 1961.

Thomas R. Shepherd has beenappointed senior vice president andgeneral manager of GTE Entertain-ment Products Group. Shepherd,who succeeds Frank R. Lann, willcontinue to be located at groupheadquarters in Batavia, NY.

Robert G. Lynch has been ap-pointed vice president -marketing forthe Products Group of GTE. Lynchsucceeds Thomas H. Cashin.

The formation of the SylvaniaCircuit Products Division has beenannounced by Roger W. Slinkman,senior vice president -componentsfor GTE Consumer Electronics. The

new division, formerly known as theSylvania Circuit Module Operation,will be headed by Abdulgafoor M.Serang, who has been named vicepresident and general manager.

Csaba Geczi has been appointedgeneral manager of the Antennasand Accessories Division of ChannelMaster. Geczi, who has been withthe company for eight years, willoversee the major portion of Chan-nel Master's production facilities inEllenville, NY.

Ervin Kuczogi has been appointedgeneral manager of Chroma Tube,Channel Master's plant for colorreplacement tube manufacturing inWhite Mills, PA. Kuczogi was chiefCRT engineer at Chroma for sixyears.

Robert Hynes has been namednational sales manager for PhilipsTest & Measuring Instruments.Hynes has been with PTMI since1974, and most recently served aseastern sales manager.

Paul F. Bugielski has been pro-moted to product manager -micro-phones and circuitry products,Shure Brothers. Bugielski will haveresponsibility for new product mar-ket planning and management, andtechnical field sales support for thecompany's microphone and circuitryproduct groups.

Vaco Products has announced theappointment of David O'Brien aswestern regional sales manager.O'Brien will be responsible for allsales and rep activity in a 13 -statearea. O'Brien will be headquarteredat Vaco's Western Distribution Cen-ter in Gardena, CA.

Harry A. Sanders, electronicsprogram instructor at Clover ParkVocational -Technical Institute inWashington State, has written a2 -page technical report concern-ing the two types of quadraturedetector circuits which are found inmost tube -type television receivers.Sanders compiled the report whenthe textbook he was using failed toprovide information that the stud-ents needed. El

ho epairsoreakes andodels

f tunershan

anyone?

u... ..... ....... ...... ................ .iii..

PTS ELECTRONICS, INC.the Only Nome You Need To Know



A second lookcit waveForms,pcwe 2

By Gill Grieshaber, CET

Most explanations of the vertical -output stage in a tube -powered TVreceiver describe the main functionas power amplification for drivingthe yoke. This amplification isthought to be moderately linearwith only a small amount of distor-tion introduced intentionally tocancel yoke and transformer distor-tion.

That explanation appears to beverified by the Figure 1 waveforms.Obviously the plate waveform of thelower trace is an inverted andamplified image of the top tracegrid waveform.

Misapplied theoryThe circuit operation seems to be

logical and correct, but that is nothow the circuit works. Any trouble-shooting based on this false theorywill produce incorrect results. Thosestatements will be proved by manyfacts.

Wrong signal amplitudesOne warning sign is the large

signal amplitudes that do notmatch the dc voltages. For exam-ple, it's impossible for any class Aor class AB tube amplifier stage tohandle an input of 470 V peak -to -peak with a grid/cathode bias ofonly -50 V.

To produce large output signalswithout excessive distortion, linearaudio amplifiers must position thecenter of the input waveform at theoptimum bias point. Also, thepeak -to -peak input amplitude can-not exceed the bias. If the ampli-tude exceeds the bias, the griddraws current, clipping distortionoccurs and dc voltage is generated.

For example, if the large inputsignal of Figure 1 was applied to a

Many previous explanations about TV vertical -sweep theory aretotally wrong. Correct operation is covered in detail here alongwith the necessity for certain waveforms, how to analyze verticalwaveforms and several tips for servicing vertical sweep circuits.

single tube operated with class ABbias, the tube could not handle the235 peak volts above and the 235peak volts below the nominal -50V of grid/cathode bias. Instead,grid current would flow, thusclamping the positive peak andproducing about -235 V of bias.However, that is not happening inthe vertical -output stage as provedby the lack of a high negativevoltage. The same dc voltage ispresent at each end of the gridresistor.

According to these facts it isimpossible for the vertical -outputtube to amplify the total pulse/sawtooth amplitude that is appliedto the grid.

Instead, a positive voltage fromthe linearity control moves the biasvoltage point so it crosses the gridwaveform at about the center of thesawtooth portion. This allows abalanced swing of sawtooth signalvoltage around the bias point. Atthe sawtooth negative peak tip, theoutput -tube current must be zero;therefore, the pulse amplitude can-not affect the plate current.

Plate amplitude is limitedSignal amplitudes at the plates of

vertical -amplifier tubes range be-tween 800 VPP and 1500 VPP.Such large voltages cannot beproduced by amplification.

Without ringing or resonance noamplifier can produce an outputsignal of higher peak -to -peak volt-age than the power supply dcvoltage. When a tube is cut off bybias, the plate voltage rises tothe supply voltage level. If a tubecould be saturated completely, theplate voltage would be zero. There-fore, the maximum range of signal

voltages is between the supplyvoltage and zero.

A vertical amplifier with +255 Vbetween plate and cathode (as inthe CTC10) never can have morethan 255 VPP of amplified signal atthe plate. The plate sawtooth hasan amplitude of 90 VPP, which iswell within the tube's capability.The other 1300 VPP of pulseamplitude is generated by ringingof the output transformer and thedeflection yoke.

Before the true output operationis explained, consider another caseof misapplied theory.

Correct yoke waveform?Many TV textbooks and home -

study courses have made the state-ments and shown the drawings ofFigure 2. The usual rationale toexplain the pulse/sawtooth wave-form of the vertical yoke is asfollows:(A) When the voltage sawtooth

Figure 1 Similarity of the vertical -output grid waveform (top trace) andthe output plate waveform (bottomtrace) appears to verify that only linearamplification with inversion has oc-curred.


A VOLTAGE SAWTOOTH TO A RESISTANCE PRODUCES A SAW TOOTH OF CURRENTA

A VOLTAGE PULSE TO AN INDUCTANCE PRODUCES A SAWTOOTH OF CURRENT

_10001_B

THEREFORE. A COMBINED PULSE/SAWTOOTH TO BOTH RESISTANCE AND INDUCTANCE

PRODUCES A SAWTOOTH OF CURRENT

= if//True? or False?

Figure 2 This is the explanation given most often in textbooks for thecombination sawtooth/pulse waveform at the vertical yoke. However, it iswrong. Yoke inductance is not sufficient to produce a sawtooth at that pulserepetition frequency. Instead, the sawtooth part of the waveform produces thedeflection.

waveform is applied across a pureresistance, a sawtooth of currentflows through the resistance.

asawtooth of current when it isapplied to a pure inductance (onewithout any dc resistance).(C) Therefore, the vertical windingof a TV deflection yoke should besupplied with a voltage waveformthat combines the correct propor-tions of sawtooth (for the resistance)and pulse (for the inductance).

Statement A is completely cor-rect. Statement B is correct if aproper match is made betweenpulse repetition rate and the in-ductance. But the summary instatement C is wrong. Actually, thevertical yoke is supplied with asawtooth of current, then the pulseamplitude is developed by yokeringing from the sudden cessationof current.

Tube produces sawtooth onlyAny plate signal produced by

amplification will be present in theplate/cathode current. To showcurrent variations, a 3.352 resistorwas added between the 6EM7cathode and the other components(Figure 3). The resistance is toosmall to affect the normal opera-tion, but the current produces avoltage drop, and a scope con-

VERT

OUTPUT

1/2 6EM7

+ 376VTO VLRT

OUTPUTTRANS

1400V PP

1.3 ADDED{ TO SCOPE

R172

.1700

R124

8200

10148

50K

TO

CONVERGENCE

YOKE

Figure 3 A 3.3Q resistor was added tothe output cathode circuit. A scopeconnected across the resistor showedthe waveform of plate/cathode cur-rent. No pulse amplitude appeared inthe waveform.

nected across the extra resistorshows the waveform of cathode -to -plate current.

Top waveform in Figure 4A isthe 470 VPP combination pulse andsawtooth between grid and cathode

iWho.rebulds

all majorbrands ofmodules?

age

TS ELECTRONICS, INC.The Only Name You Need To Know'4

4



Waveforms

of the 6EM7 tube. For the bottomwaveform, the scope gain wasincreased until the 90 VPP of thesawtooth filled about half of thescope screen. A zero -voltage linewas added by the scope.

An analysis of Figure 4A lowerwaveform reveals that the instan-taneous grid/cathode bias variesfrom about -90 V at the start ofvertical deflection (left part of thesawtooth) to just a few volts morenegative than zero. Although theprecise cutoff bias voltage of thetube is not generally know, it seemsdefinite that none of the pulse willaffect the plate current, since allof the pulse is more negative thanthe cutoff bias where the current iszero. Increasing the negative bias

beyond the cutoff point can'tproduce less than zero.

Figure 4B shows the plate/cathode current waveform (scopedacross the added 3.3Q cathoderesistor) along with the average -current line (near the center) andthe zero -current line (at the bottomof the waveform).

At the zero -current line, eachfalling edge of the sawtooth (whichrepresents the retrace) extendsslightly below the line. Of course,no tube can draw less than zerocurrent; therefore, these smallnegative tips must be caused by thelarge grid pulse feeding through thegrid/cathode capacitance.

The current waveform clearlyshows that zero current flows at the

Figure 4 Top waveform of picture A is the usual waveform between grid andcathode. Lower trace is the same signal expanded by gain of 20 V/div and witha zero -voltage line added by the scope. During the sawtooth the instantaneousgrid voltage went from about -93 to about -3 V. The B waveform is the cathodecurrent across the 3.3Q resistor with an average -current line (near center) and azero -current line added by the scope. The small negative pulses are not causedby plate/cathode current because control adjustments did not change the pulseamplitude.

Figure 6 Control adjustments changed the pulse amplitudebut not the sawtooth amplitude. Picture A shows thenormal output -plate waveform when the picture hadnormal height and good linearity. When the height controlwas turned fully clockwise and the linearity control wasadjusted for the same total height as before, thewaveform (B) showed unchanged sawtooth amplitude but

beginning of vertical deflection (leftend of the sawtooth slope) andincreases at a slightly non-linearrate to the maximum.

No trace of amplified pulses wasfound in the current waveform. Butto make certain the lack of pulseswas not produced by critical heightor linearity adjustments, those con-trols were adjusted over their fullranges while the current waveformwas observed. No pulses appearedin the waveform.

Yoke currentIt does not seem possible for

vertical tube plate current thatvaries between zero and positive toproduce yoke current that mustvary from negative to positive with

Figure 5 When the waveforms wereexpanded horizontally by the Tektronixmodel T935A scope, the grid pulse atthe top was wider than the plate pulse(bottom trace). This difference indi-cates the output pulse was notproduced by simple amplification.

increased pulse height. The raster was compressed at thetop. For waveform C the linearity control was rotated fullyCCW and the height control was adjusted for a totalpicture height that equalled A. The linearity was spread atthe top. Therefore, total height (disregarding nonlinearity)is determined by the sawtooth amplitude and not thepulse height.


zero in the center during both traceand retrace. But the two arecompatible because the tube cur-rent does not drive the yokedirectly. Instead either a capacitoror a coupling transformer removesthe dc. The sawtooth yoke currentis symmetrical. Therefore, in theabsence of dc, the zero -current lineis exactly in the center.

Effects of controlsAt the vertical -output grid, height -

control variations changed the am-plitudes of both the pulse andsawtooth sections. Adjustments ofthe linearity control (which changesthe grid/cathode bias) moved thezero -voltage line nearer or fartheraway (less or more negative bias)from the tip of the sawtooth. Whenthe adjustment tried to move theline below the tip (positive gridbias), the sawtooth tip was clippedbecause of grid -current loading,and the clipping caused bottomfoldover on the TV screen.

Wider/narrower pulsesMore evidence is found in Figure

5 waveforms where the grid andplate pulses have been expanded bythe scope. The grid waveform ismuch wider, indicating that itoriginated as a square -tipped pulse.By contrast, the plate pulse has asharp tip and the general look of apulse formed by highly -dampedringing.

Pulses versus heightOne of the handicaps of believing

incorrect basic theory is that oftenthe wrong parameters are mea-sured, leading to confusion anderrors. That can happen if atechnician judges the amount ofvertical deflection by the amplitudeof the total waveform, which iscomposed mostly of pulses. Thefallacy of judging sweep by pulseamplitude is illustrated by the nextfew waveforms.

Figure 6A shows the normaloutput plate waveform for a fullraster having good linearity. The Band C waveforms have differentkinds of poor linearity, but theyalso have the same raster height asA.

Remembering that all three TVrasters had the same total height,carefully examine the sawtoothamplitude and the pulse amplitudein each of the three scope wave-forms. The three sets of pulses havedrastically different amplitudes, butthe sawtooth amplitudes are thesame for all three waveforms.

Therefore, the sawtooth ampli-tude of the vertical yoke waveformdetermines the raster height on aTV screen. Pulse amplitude in thecombination waveform has no par-ticular significance except that eachmodel has a certain normal ampli-tude.

60 -Hz injection test-A quicktest for multivibrator vertical -sweepcircuits is to connect a 0.1 capacitorbetween the 6 V heater voltage andthe oscillator grid or the output

Figure 7 Picture A shows the output tube grid waveform at top and the platewaveform (bottom trace) when a 60 -Hz sine wave was injected at the oscillatorgrid. Controls were adjusted for full height with fair linearity on the TV screen.Picture B top trace is the grid waveform and the bottom trace is the platewaveform when 60 Hz was injected at the output grid. Height was about 5inches, but the linearity was severely stretched at the top of the TV raster.These waveforms reinforce the statement that the sawtooth (not the pulse)determines the height.

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Waveforms

grid. Normal TVs show some heightthen, although the linearity is notgood and the picture rolls steadilydownhill during color programs.

Waveforms for the CTC10 whenthe sine wave was injected at theoscillator grid are shown in Figure7. Top trace of Figure 7A is theoutput -grid waveform while theplate waveform is shown by thebottom trace. Controls were ad-justed to obtain full height with fairlinearity. Notice that the pulses aresmall.

In Figure 7B when the sine wavewas injected at the output grid, thetop trace is the output grid wave-form, and the bottom trace is the

output plate waveform. The TVpicture had a 5 -inch height with

poor linearity. No pulses are pre-sent in either waveform, againproving that pulses are not requiredfor vertical deflection.

Although a 60 -Hz sine wave wasinjected in both tests as a substitutefor an oscillator signal, no trace ofa sine wave was found at the outputplate. Rectification by the first gridit reached changed the sine waveinto wide and distorted pulses thatwere further modified by the wave -shape R/C filters into approxima-tions of the correct output platewaveforms.

Solid-state proofThe output waveforms of solid-

state vertical systems usually have

small pulse amplitude and largersawtooth amplitude. Some circuitshave diodes to clip the pulses(strong pulses can ruin transistors)while others have pulse clipping asa hidden byproduct.

All these items of proof empha-size that the pulses are not essen-tial. In tube circuits, they producefaster retrace, and the high ampli-tudes are tolerated because they areharmless. The design of solid-statecircuits deliberately minimizes thepulses. In all cases, it is the saw -tooth part of the waveform thatcauses vertical deflection.

Waveform exceptionsAfter a thorough study about the

distortions of a square wave as it

145V PP 380V PP

W3

R165 1 R166

W4

C133 1.0068

-43V

100V PP R158

1/2 6EM7

VERT OSC

5

390K

1200V PP 1400V PP

W2

C142

W1

47k 1 100KC135 680 pF R168

C13T80 pF

1M

VERT HOLD

Waveform Analysis

.0082

150K1/2 6EM7

VERT

OUTPUT

Figure 8 These are the component values and peak -to -peak signal voltages measured in the positive -feedbackpath of an old RCA CTC10.


passes through various resistance/capacitance filters, a technicianshould be able to follow a sche-matic and know approximatelywhat the waveshape should be ateach point.

However, there are exceptionsthat complicate the analysis be-cause of multiple paths or theunexpected conduction of a diode.Some examples will be shown in thewaveform analysis of vertical sweep.

Vertical -feedback waveformsAs previous discussions have

settled questions about the properoutput waveform at the vertical -output tube in an RCA CTC10chassis, the remainder of thatsweep circuit will be analyzed, withthe emphasis placed on uniquewaveforms.

Figure 8 shows the positive -feedback path from the plate of the6EM6 output tube to the oscillatorgrid. (Of course, both stages makeup the multivibrator oscillator. Butthose labels are easier to keepstraight.) The corresponding wave-forms are in Figure 9.

W1 waveform has been analyzedbefore as consisting of sawteeth andpulses.

Capacitor C142 and resistor R168form a high-pass (low -frequencycut) filter. Therefore, the W2waveform is similar to W1 exceptthe sawtooth tilt has been removedand the amplitude is slightly lower.

The tilt should be removed atW2 to prevent a problem furtherdownstream. Before the pulsewaveform reaches the oscillator, theamplitude must be reduced and allhorizontal -sweep pulses removed bylow-pass filters. Both are done bythe R166/C138 and R165/C135filters, that incidentally reduce thepulse amplitude more than thesawtooth amplitude. Unless thesawtooth tilt is removed before thelow-pass filters, it will be excessiveat the oscillator. Those pulses don'tcontribute any deflection, but theyare used for oscillator feedback.

W3 shows the reduced amplitudeand the rounded corners producedby the R166/C138 low-pass filter.

Those effects are more pronouncedfollowing the R165/C135 filter.Notice that the sawtooth tilt is moreprominent as the pulse amplitude isreduced.

None of these previous waveformsneeded zero or average lines. How-ever, those lines will be valuable inanalyzing W5.

Knowledge gained from square -wave analysis predicts that the W5waveform should be identical toW4, with the possible exceptions ofless sawtooth tilt and the additionof some dc voltages from the gridcurrent. But the W5 waveformseems to be totally different fromW4. Common sense cannot explainwhy it is different.

Oscillator -grid waveformPositive -going W4 pulse passes

through C133 and causes diode -type conduction between grid andcathode. This clamps the positive

of waveform zero(Remember, it was started lastmonth that clamping a positivepeak produced negative voltage.)Therefore, the trailing edge of thepulse plunges to about -93 V.Follow this series of actions in WSof Figure 9.

The trailing edge of the pulse inW5 ends at about -93 V. At thegrid (after the waveform has passedthrough C133), it seems logical thatthe base line between pulses will beflat, because C133 should haveremoved the sawtooth tilt. However,C133 is too small to hold thecharge without loss for the amountof time between pulses. So, C133discharges through R158 and R159Aat a rate that follows the text -bookvoltage -discharge curve (except it isinverted since the charge is nega-tive.)

C133 continues to discharge to aless -negative voltage. At about -16V, the oscillator barely begins todraw some plate current. If left toitself, the circuit will oscillateshortly afterward, because the oscil-lator current drives the output, andits pulse in turn drives the oscillatorgrid. At this time, however, thevertical sync arrives and it forces

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Waveforms

W1

W2

i

'`-.....,,....

Figure 9 Numbers of these waveforms correspond toFigi re 8 schematic. The Tektronix scope has added azero -voltage line near tl-e top and the average -voltageline near the center of -he W5 waveform.

the output tube into conduction abit sooner. That starts the regenera-tive effect. A less -negative oscillatorgrid allows more plate currentwhich reduces the grid voltage ofthe output tube. In turn, thereduced grid bias increases theoutput plate voltage, and it iscoupled through the positive feed-back loop to the oscillator gridwhere the rising pulse triggers theoscillator into conduction. Thisentire regenerative cycle occurs toofast to be seen on the scope, but itends with a large positive pulse thatis applied through C133 to theoscillator grid. In fact, the wave-form WS shows that the pulsetravels to about +7 V before thegrid current clips it. That accountsfor the 45 V difference between W4and WS.

Next, the grid/cathode currentclamps the waveform again; thepulse trailing edge goes negativeand the slow C133 discharge allowsit to drift toward zero volts. This isslightly more than one verticalcycle.

LockingTwo conditions must be met for

the vertical circuit to lock properly.The R/C time constant (C133 andR158/R159A) at the oscillator gridversus the maximum negative chargein C133 must be adjusted to causethe oscillator to operate slightlyslower than the 59.95 -Hz field rate.Then the sync starts the cycle at theright time for correct locking.

C133 has a fixed capacitance, butthe resistance of the R/C circuit isadjustable. This ability to adjustthe time constant is necessarybecause a different pulse amplitudereaching C133 will change thedischarge time and thus the oper-ating frequency. Therefore, even achange of picture height varies thefree -running frequency.

For example, if the picture islocked and then the height isincreased moderately, the negativeC133 charge is increased and (if thelocking is not tight) the vertical willroll upward very rapidly.

Zero and average lines-The topline in W5 is the zero -voltage line.

20 Elecifronic Servicing July 1979

Only those pulse amplitudes slightlyabove and below the line are in thebias range that can cause oscillatorplate current. Therefore, all of WSwaveform is more negative thancutoff bias except the positive pulsethat causes conduction. In turn, thetube conduction produces negative -going pulses (which cannot bescoped directly) at the plate.

The line near the center ofwaveform W5 is the average -voltageline. It was stated last month thatthe peak voltage between the zeroand average lines equals the devoltage as measured by a meter.Both the scope and a de meter gavereadings of -43 V.

This -43 V of grid bias is not anabsolute voltage. It varies withheight changes and with adjust-ments of the vertical -hold control.In fact, the voltage can be bent afew volts either way by moving thehold control within the limit of thelock -in point. But if the voltagevaries because of capacitor leakage,resistor drift or other variables, thevertical -sweep frequency will changeand locking will be lost.

Waveforms without gridloading

C142 was disconnected from thetube, and while the TV power wasoff, positive -going narrow pulsesfrom a VIZ generator were con-nected to C142 in an attempt toduplicate the normal sweep wave-forms (W2, W3, W4 and WS). Theexperiment was not successful. Thewaveforms changed according tosquare -wave theory, but they didn'tmatch the actual ones.

Finally, a separate positive -feed-back network was breadboarded.The values of C142, R168, R166,C138, R165, C135, C133 and R158/R159A were measured and wiredtogether. The vertical sweep wasworking normally, and the extranetwork was connected only tooutput plate and to ground. All ofthe W1B through W5B waveformswere measured and photographed(see Figure 10). No tube or transis-tor was connected to the WSBwaveform.

Of course, W1B is identical to

Oi

Figure 10 To determine how the Figure 9 waveformswould change if the oscillator grid current wasremoved, a separate positive-feedback path wasconstructed without any dioce at C133. These wave-forms follow square -wave theory for such filters, thusproving that oscillator grid current produces theunique W5 grid waveform.


Waveforms

the original W 1. Other waveformsshowed only a slight rounding ofthe edges, and the pulse amplitudeswere much higher than the actualones. The sawtooth tilt was smallerby comparison with the largerpulses. But the important waveformwas W5B. It was virtually identicalwith the original W4.

Could the lack of a tube grid/cathode at W5 account for the hugechange of waveform? A diode wasconnected at W5B as a substitutefor the oscillator tube, and the newW5B waveform was identical withthe original W5. All other wave-forms then were identical to theircounterparts, including the ampli-tude.

Therefore, all deviations from thewaveforms predicted by square -wave theory were caused by grid/cathode current of the oscillatortube!

Oscillator/amplifier waveformsFigure 11 shows the RCA CTC10

oscillator and power -amplifier cir-cuits that were not included in theschematic of Figure 8. Matchingwaveforms are in Figure 12.

The W5 waveform in Figure 12was described previously in Figure9, where the zero line proved thatonly the small positive tip providesthe low bias necessary for a flow ofplate current. The pulse -shapedbias should produce a larger nega-

tive -going pulse at the plate. A100 C resistor was added betweencathode and ground, and the W6waveform scoped across it verifiedthe narrow pulse of current.

However, the W7 plate waveformdoes not show the predicted pulses.Instead, the waveform is a combi-nation of pulses and sawteeth.What component or circuit actionadded the sawteeth?

Creating sawtooth waveforms-Acombination of pulses and sawteethcan be obtained as shown in Figure13 by connecting a resistor and acapacitor in series from the V107Aoscillator plate to ground.

To visualize this action the

C134

SYNC .--.027

RI55

VERT

OSC

112 6EM7

100V PP

101!ADDED

+56VFROM

LIN CONTROL

+ 393VC139

I(

R169 2.2M

R140MA.1000

R167 2.2M

R120B

C137

+ 703V

HEIGHT 2.5M

T.22

B+

Waveform Analysis21V PP

470V PP

W8

i

VERT

OUTPUT

1/2 6EM7

4-3761/

+55V

B -BOOST

3

+119V

3.3 ADDED TO SCOPE

1400V PP

C144 .47

R172

4700

R124

8200

TO VERT

OUTPUTTRANS

10148

50µF

TO

CONVERGENCE

YOKE

Figure 11 This schematic completes the Figure 8 schematic and shows the RCA CTC10 amplifying path. WaveformW5 is the same in both diagrams. Two resistors have been added to permit viewing of oscillator and output -cathode current waveforms. Corresponding waveforms are in Figure 12.


easiest way, imagine that C134capacitor is shorted which leavesonly R155 from plate to ground.The dc and signal levels are greatlyreduced, but the waveform showsnegative -going pulses and nothingelse.

Next, imagine that R155 isshorted but C134 is okay. C134 isconnected from plate to ground,and the pulses are integrated intosawteeth.

Therefore, when both the resistorand capacitor are in the circuit, thewaveform is a combination of bothpulses and sawteeth. Larger resistorvalues increase the pulse amplitude,and a larger capacitance decreasesthe sawtooth amplitude. Thesevalues can be varied to obtain thedesired pulse/sawtooth ratio.

The actual Figure 11 circuit addsone more function. Filtered verticalsync is injected between C134 andR155, thus the R/C filter does twofunctions. Negative -going sync en-ters through C134 to reduce theoscillator plate voltage and controlthe locking.

Height adjustment-The gain ofan audio tube is increased when theplate -load resistance is increased.Gain of an oscillator (pulse ampli-fier) is not changed by the plateresistor, but other factors determinethe output amplitude as the resis-tance is varied. In vertical circuits,for example, a larger total resis-tance from B -boost to oscillatorplate decreases the pulse/sawtoothwaveform amplitude. And a smallerresistance increases the amplitude.

Figure 14 explains the separateactions for pulses and sawteeth.

More waveformsWaveform W8 (output grid) in

Figure 12 is identical to the W7waveform at the oscillator plate.Any difference indicates a defect.C139 coupling capacitor and R169output grid resistor both have largevalues, and such a long R/C time

Figure 12 These are the waveforms of Figure 11

schematic.


OS+C

1

NEGATIVE. 60 HzGOING

PULSES

68K

10K

.22

PULSES

PULSES AND

SAWTEETH

SAWTEETH

C134

R120B SYNC INPUT

R155

B

C139PULSE/

SAWTOOTH

B+

Combined Pulses and Sawteeth

C

Figure 13 (A) Negative -going pulses (top trace) from VIZ model WA -549Acan be changed into sawteeth (center trace) and combination pulse andsawteeth (botto n trace) by the B schematic. (C) The CTC10 schematicdoes about the same as the previous circuit. However, some of thecomponents are hidden. In effect, the pulse enters at the cathode, withthe plate resistance representing the 68K resistor of B, while the 10Kresistor and the .22 NF capacitor take the place of R155 and C134.Therefore, the pulses appear in the cathode current but cannot be scopedanywhere else.

Waveforms

constant passes the pulse/sawtoothsignal to the grid without tilt or anyother significant change.

Bias of the output tube is deter-mined by the amplitude of the gridwaveform versus the positive voltageat the grid. This positive voltagecomes from the linearity control,and it moves the grid/cathode zero -voltage line nearer or farther fromthe positive tip of the sawtooth.These factors determine the flow ofoutput -tube current at the begin-ning of deflection (top of TVraster).

Incidentally, don't rotate thelinearity control any more clockwisethan barely enough to provide goodlinearly at the top of the picture. Asthe grid -to -ground positive voltagerises, the cathode do voltage risesalmost in step. Notice that thecathode -to -ground voltage effectivelysubtracts from the B+ supply.Therefore, an excessive linearitysetting prevents full deflection atthe raster bottom. For a TV thatwon't quite fill the screen, back offthe linearity and increase theheight -control setting.

Cathode waveform W9 is almostidentical to the cathode -currentwaveform of Figure 4B. That'sbecause most of the cathode by-passing by C148 is through theconvergence -circuit resistance. Wave-form W10 is the output -tube platewaveform which has been analyzedbefore.

Tips for servicing verticalsweep

Multivibrator-type vertical -sweepcircuits have caused many problemsfor technicians over the years.Because of the closed loop, thesymptoms have been confusing. Abad waveform at one point prob-ably ruined the waveforms atothers. Defects that would havereduced the height alone (if thecircuit only amplified) also caused awrong frequency with severe loss oflocking. On the other hand, a largechange of frequency often reducedthe height.

Observant technicians have no-ticed that linearity and heightadjustments often varied the verti-cal frequency sufficiently to cause aloss of locking. Also, they noticedthat defective components far re-moved from the hold control pro -


duced severe frequency errors thatwere impossible to correct with thehold control.

Many of these puzzling cases canbe explained by a clear understand-ing of the charging and dischargingof the R/C time -constant that ismostly at the oscillator grid circuit.Any defect of those componentschanges the operating frequency.

The amplitude of the pulse thatcharges the time -constant capacitor(C133 in Figure 8) is very critical.In the previous discussion, it wasassumed that the postive-feedbackpulse originated at the input end ofC133. That's only approximatelycorrect. This amplitude is deter-mined by the pulse voltage at theoutput plate plus all of the compo-nents between there and C133.

For example, an open C135increases the pulse amplitude atC133, which increases the C133charge. That higher negative volt-age requires longer to leak away, sothe vertical frequency is reduced(picture flips upward rapidly). IfC138 has a leakage of 100K, thepulse downstream at C133 is re-duced to about half amplitude. Thenegative voltage is lower, the fre-quency is higher and the picturerolls down.

Further complications arise be-cause all the positive -feedback com-ponents are in series with the inputside of C133 during the dischargepart of the cycle. Where can C133discharge to if R168 is open? R165,R166 and R168 all affect thedischarge time. That's why ashorted C142 changes the frequencyso drastically; it has the effect ofshorting out the 150K resistance ofR168.

Heat changesOne of the typical vertical prob-

lems is a slow downward movementof the picture after the receiver isthoroughly warmed. A leaky C133that's sensitive to heat is a likelysuspect. Heat it slightly with asoldering iron and then cool it withcanned coolant as a test. Don't usean oridinary disc ceramic as areplacement.

Check the positive feedbackNormal amplitude reduction in

the positive feedback loop of most

vertical multivibrators occurs inseveral gradual steps. This fact canbe the basis for a fast test of thefeedback loop, if there is somepicture height. Any large amplitudereduction indicates a defect at thatpoint or in a component justupstream.

One prime suspect is any capris-tor (combination capacitor andresistor). Many have been trouble-makers. Replace them with separ-ate components of the same values.

These quick checks plus an

understanding of the true circuitoperation should make vertical -cir-cuit repairs much easier.

Editor's Note: Similar combinationsof updated circuit theory andpractical tips should be helpfulwhen applied to other electronicsubjects. Send your comments orquestions to:

Carl BabcokeElectronic ServicingP.O. Box 12901Overland Park, KS 66212 O

A

(OSC)

B+

Making Pulses

R120 B

C134

B Making Sawteeth

.1111.1I

amá

Figure 14 Variations of R12OB height control's resistance affects theamplitudes of both sawteeth and pulses, but the operation is different. (A)Negative pulses are formed by oscillator tube conduction. When the tubedoes not conduct (switch open), the positive voltage between pulses isdetermined by the R12OB/R155 ratio. Larger R12OB resistance reducesthe maximum positive voltage. (B) Sawtooth amplitude is determined bythe time constant of R12OB and C134. When the resistance of R12OB isincreased, C134 cannot charge to the previous higher voltage before thenext cycle begins with tube conduction which discharges the capacitor.Therefore, the amplitude is smaller.


Digital numbering systems

Various number codes are em-ployed to describe the operationsand programming of microproces-sor equipment. These codes areextremely valuable for reducinghuman operator errors and mini-mizing the lime necessary forprogramming.

Codes reduce errorsAs a practical demonstration of

By Jack Webster

Any combination of numbering systems can be used with micro-processors. Therefore, digital technicians must know the basicfacts about each system, and be able to convert from one toanother. Methods are given here.

codes, copy the next two series ofnumbers. The first series is:

11001010101101001001101011000101

Errors can easily occur whenwriting these long series of num-bers. But those 8 -digit binary num-bers are typical of the instructionsgiven to microprocessors. Many

Comparisons of number systems

HEXA-DECIMAL BINARY OCTAL DECIMAL

0 0000 0 01 0001 1 1

2 0010 2 23 0011 3 34 0100 4 45 0101 5 56 0110 6 67 0111 7 78 1000 10 89 1001 11 9

10 1010 12 A11 1011 13 B12 1100 14 C13 1101 15 D14 1110 16 E15 1111 17 F

microprocessors use 8 -bit numbersin groups of one, two or threebytes.

Write these numbers and checkthem for mistakes:

2B20F196

Two letters or numbers are mucheasier to handle accurately than theprevious 8 -digit bytes. The lastexamples are in hexadecimal code,and each represents a complete8 -bit byte.

If a keyboard is used to programa microprocessor for a certain job,hexadecimal code numbers aretyped. However, internal circuitsconvert those hex code letters andnumbers into 8 -bit binary bytesthat are sent to the microprocessor.

Also, the octal code frequently isemployed in microprocessor opera-tion. Each three -octal digit repre-sents an 8 -bit byte. These areexamples of octal numbers:

142056101110

The last two numbers could bemistaken for binary code, so it isobvious that some confusion canoccur when the type of code is notknown.

RadixWhen there is danger of wrong

identification of codes, the numberis marked with its radix. The radixof a numbering system is thenumber of symbols required towrite any number in the system.For example, ten symbols are usedin the decimal system, so it has aradix of 10. The binary system has


a radix of 2, the octal system radixis 8, and the hexadecimal radix is16.

The radix is written as a sub-script beside the number whenidentification is desired to preventconfusion and errors. The followingare examples of the number 11 aswritten in four systems:

Binary 112 (equals decimal 3); Octal 118 (equals decimal 9); Decimal 1110 (equals decimal

11); and Hexadecimal 1116 (equals

decimal 17).A comparison of the first sixteen

numbers in each system is providedin Table 1. These are the number-ing systems most often encounteredin microprocessor instructions.

Converting one system to anotherOctal and hexadecimal numbers

are more convenient for humanoperators, but a microprocessor canaccept only binary numbers. There-fore, it is necessary to convert thenumbers of one system to those ofanother.

Procedures for number conver-sions are very simple and easy toremember. Examples of 8 -bit num-bers will be used since they are themost common in microprocessors.

Binary to octalDividé the binary number into

groups of three digits, starting atthe right and ending at the left. Ifthe last group at the left does nothave three digits, add zeros tocomplete the three. (This does notchange the value of either thebinary or octal number, but itsimplifies the calculation.)

Here is a sample calculation:number to be

ReviewAll signals inside a micro-

processor (and signals into orout of it) must be in digitalform (highs and lows). EachBinary digIT is called a bit,and a group of bits is called abyte. Many microprocessorbytes have eight bits.

Microprocessor memories areof two types. Read -Only -Memory (ROM) ICs have thedigital information perma-nently stored inside. This datacan be retrieved as often asneeded, but it can't be changedor erased. Random -Access -Memory (RAM) ICs are theread/write type that can ac-cept data for storage. Thedata can be retrieved asneeded, or new data can bestored to replace previousdata.

Most of the explanationshave been about RAMs be-cause they have nothing storeduntil data is programmed intothem. This important extrastep must be understood.

used for both examples. So, theresults can be stated as: 110111102= 3368 = DE16.

Octal to binaryThe binary -to -octal conversion

that was explained before is re-versed here.

number to beconverted 143

change each tobinary 001 100 011

combine but dropleft zero 01100011

converted 11011110 Therefore, 1438 equals 011000112.groups of three

digits 011 011 110 Hexadecimal to binaryoctal value from table 3 3 6 Essentially this is the reverse of

Therefore, 110111102 equals 3368.

Binary to hexadecimalThis procedure is similar to the

previous conversion to octal, exceptthe binary numbers are separatedinto groups of four digits.

number to beconverted 11011110

groups of four digits 1101 1110hexa value from table D ETherefore, 110111102 equals

DE16.The same binary number was

the binary -to -hexadecimal conver-sion.

number to beconverted 4C

change to 4 -digitbinaries 0100 1100

combine into8 -digits 01001100

Therefore, 4C16 equals 010011002.

Other codesStudies of other number codes

will be necessary as the micropro-cessor course continues. O

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For more informationon Ansafone 696, fill in

the coupon or call toll -free:

800-431-1710(In New York call 914-967-3810)

Name

Title

Phone

Company

Address

City State 7ip

Mall to: Dictaphone Corporation105 Oak StreetNorwood, New Jersey 07648

Dictaphone and Ansafone are trademarks of DictaphoneCorporation, Rye, N.Y. IES-79 a



Highlights of1980 products

These are summaries of 1980 TV, audio and videocassette product lineslisted according to manufacturers.

General ElectricHighlights of the 1980 General Electric line include

a simplified and improved VIR Broadcast -ControlledColor system, the new 19 -inch EC (Energy Conscious)chassis, crystal -controlled all -channel tuners, micro-processor -controlled infra -red remote controls and afour-hour VHS videocassette recorder.

Three types of Quartz tuning are offered. ModelET82 tunes in all VHF and UHF channels with threerevolutions of one knob. Rotary switches manuallyselect proper inputs of the programmable divider inthe phase -locked loop (PLL) which is the same for thethree systems. Model MMP82 has a random-accessmanual pushbutton keyboard. MP82 also has micro-processor -controlled tuners plus all -channel program-mable remote control. Either random-access orautomatic scan of programmed channels may beselected. The remote can be customer programmedfor up to 20 channels. Because of the phase -lockedloop, there is no need for any manual or automatic

fine tuning. Channels are indicated by digitalreadouts.

Color Monitor II operates when the VIR switch ison but the station has no VIR signal. It providesskin -color and saturation stabilization without ad-versely affecting other hues.

All 19 -inch GE color receivers are equipped withthe EC chassis. Five circuit boards are mountedvertically on the metal frame to allow air flow aroundthe components, and the cabinet air vents are larger.This 28 -kV chassis uses about 100 W compared to143 W for the previous model. Total reduction ofinterior temperature is about 18 F, which is said todouble the reliability.

Count -down circuits provide vertical and horizontalsignals without hold controls. High -voltage diodes are-

mounted inside the high -voltage transformer forincreased reliability. Visible 920 -kHz picture beatsare minimized by a synchronous product detector.

A new 19 -inch picture tube has 90 degree


deflection and unitized guns. Focus voltage is 8.5 kV,and auto -convergence eliminates most adjustments.

One important feature of GE's 4 -hour program-mable VHS videocassette recorder is the pushbutton12 -channel electronic tuning. The programmingallows recording of five TV programs on differentchannels for each of seven days. Also, the recorderhas a built-in electronic timer, tape counter withmemory and a remote pause.

In addition to the full line of picture tube sizes andcabinets, General Electric offers the Widescreen-1000projection TV with an internal screen that has morethan three times the area of a 25 -inch picture.

HitachiEleven color and one monochrome TV receivers

were displayed at the Consumer Electronic Show(CES). Model CK-200 is a 5 -inch portable color TVthat operates from line voltage or 12 Vdc. Theelectronic tuning has two buttons (one up and onedown) for the station search tuning.

Model CT -989 is a 19 -inch color receiver withremote, random-access station selection in addition tosearch, VIR color control and wood cabinet. Othermodels are in 13 -inch and 15 -inch screen sizes. ModelI-62 is a 9 -inch monochrome portable receiver.

A stereo portable combination is model TRK8181H that features programming. A Digital Ran-dom -Program Selector counts the times betweenselections when nothing is recorded. Using these asreferences, this circuit allows the user to selectmusical numbers out of sequence by fast forward orrewind to the desired spot. Two tweeters with twowoofers, two volume meters, microphone mixing anddigital readout of the program in progress are otherfeatures.

Model TH-6100H is a pocket -sized AM radio witha slide -rule dial and an LED for tuning indicator.

MagnavoxIncreased use of electronic tuning and improved

sound quality are two general features of the 1980Magnavox line. Loudness controls that boost both lowand high frequencies at low sound levels andincreased audio power are changes made for all19 -inch and 25 -inch models. A voice/music switch isincluded in all 25 -inch Star and Touch -Tune models,except those having separate amplifiers.

The high -resolution comb filter that provides widervideo bandwidth is included in 76% of the new TVs.

In the 5000 series are eight Star tuning systemsand 14 10 -button Touch -Tune models. All haveremote controls.

Non -remote series 4800 25 -inch color receiversfeature 10 -button electronic tuning with large LEDdigital readouts and horizontal key address. Single -

knob electronic tuning is available in five other25 -inch models. Four new 19 -inch models withremotes and Touch -Tune Videomatic are available.

Nine models have been added to Magnavox'smodular audio line.

A total of 24 home video games is offered nowafter the addition of 7 new games for Odyssey 2.

PanasonicOnly one electron gun is required in the 4.5 -inch

picture tube of Panasonic model CT -1010 colorportable which operates from nine "D" batteries.Instead of a shadow mask, stripes of specialphosphors on the screen emit ultraviolet light that isdetected and processed to control the beam landing.

The General Electric Energy -Conscious (EC) chassis isdesigned for cooler operation with a metal frame andvertically mounted circuit boards for improved aircirculation. Average ac power is 100 W.

General Electric's 4 -hour programmable VHS videocas-sette recorder permits recording of five programs atdifferent times on five days during one week. The userfollows the reminder lights for step-by-step programming.


Spokesman for Philco is Eddie Albert, well-known TV andfilm star. He will be featured in several kinds ofadvertising. Philco is brirng,ng back the former slogan,"Famous for quality the would over."

Quasar model WT5966RW 19 -inch table model color TVfeatures Compu-Matic touch tuning, which is a crystal -controlled PLL circuit. An LED readout shows the channelnumbers.

Pushbutton selection of TV channels, a digital clock andprogramming of six recording hours up to seven days inadvance are a few features of model VH5150 Quasarvideocassette recorder. One channel can be viewed whileanother is being recorded.

1980 Highlights

According to Panasonic, the TV is smaller and uses40% less power than previous color portables.

Included in all consoles and five portables is Color-

Pilot, an active circuit that adjusts color and tintaccording to the incoming program and a preselectedstandard.

All consoles feature ColorPilot, Panalock AFT,video sensor, Panabrite Control, lighted channelindicator, CATV antenna connector, and a 100degree in -line tripotential picture tube.

Panasonic also has added 26 models to the presentradio and tape recorder lines.

PhilcoThe 1980 line of Philco Color TVs offers 17 new

models in 25 -inch, 21 -inch, and 19 -inch screen sizesin console and table versions. Three models featureremote tuning. Five 25 -inch models have Color -Riteautomatic picture control; two have five -buttonremote control.

Three models feature Philco ACT (Auto -lockChannel Tuning), Super Black Matrix picture tube,lighted channel indicators and vinyl/wood cabinets.Four 25 -inch consoles have an electronic single -knobVHF/UHF tuning system.

Six Philco stereos, including two studio soundcenters, one compact (with both cassette and 8 -tracktape decks) and three consoles were introduced at therecent convention.

Philco's monochrome TV line includes 10 modelsin screen sizes from 9 -inches to 19 -inches.

QuasarAdditional models with Compu-Matic direct -access

touch tuning highlight the new 1980 Quasar line thatincludes 35 models ranging from 13 -inch to 25 -inchsizes. Three small -screen models were introduced,including a new 15 -inch with remote.

The Dyna-Module chassis is used in all models,and Dynacolor (Quasar's automatic picture -controlsystem) is included in all but one. Audio SpectrumSound with three speakers is employed in 10 models.The Compu-Matic microprocessor -controlled elec-tronic tuning system now is contained in 14 models.No pre-programming is required for any area of thecountry. Quasar also offers a full line of monochromeportable receivers, including many portables andmodels with built-in radios.

Two new six -hour VHS videocassette machinesfeature tape economy. Model VH5020 allows sixhours of recording to be programmed up to sevendays in advance. Model VH5200 is a portable player/recorder that operates from 120-V line power, 12 Vdcin car or boat or from internal rechargeable batteries.Also offered are three color cameras with pricesranging between $660 and $960.

Insta-Matic cooking with Quasar microwave ovensis accomplished with a sensor and a microprocessorwhich determine the correct cooking power and the


required time. Insta-Matic Frozen Foods allows thedefrosting and cooking of frozen foods in one step.Insta-Matic Temperature cooks foods to the desireddegree of doneness using only one control.

RCARCA has announced three major developments as

part of the company's 25th anniversary line of colorTV receivers. A color receiver that can bepre-programmed to select channels and turn on andoff over a period of seven days is one advancement.Video sharpness is improved by a comb filter using acharge -coupled device (CCD). This Dynamic DetailProcessor system is said to provide 330 -line resolutioninstead of the former 260 lines. The Dual -DimensionSound system processes monophonic audio to achievea simulated stereo sound from the TV.

In the new line, the ColorTrak models total 29, andthe XL -100 line has 16 models ranging from 13 -inchto 25 -inch sizes. Three of the 25 -inch XL -100 have asingle -knob 20 -position SignaLock varactor tuningsystem.

SanyoMany of the 1980 Sanyo color TVs have Surface

Acoustic Wave filters (SAW) which replace the IFcoils. Phase -detector circuitry and one IC are said toimprove the color fidelity. Several models featureelectronic tuning with or without remote. One 19 -inchcolor TV (model 91C41) is to be retailed at only$339.95.

The portable audio line has been expanded withnew radios, cassette decks and carry -along systemsthat include radio, cassette and TV. An AM/FMclock radio and monochrome TV has a 2.5 -inchpicture. The cabinet has 2"x5"xl" dimensions.

SonyTen Sony color TVs are introduced for 1980. The

three consoles have 26 -inch Trinitron single -gunpicture tubes, the largest size available (341 squareinches versus 315 square inches for 25 -inch sizes).Some features include the Alpha chassis, which hasfewer components using less current to operatecooler, Velocity Modulation design of the picture tubeto give better corner -to -corner sharpness, automaticor semi -automatic channel presetting, Lumisponderlight sensor that changes brightness and contrastaccording to the room lighting, fluorescent digitalclock and channel indicator (some models) and theExpress Commander infrared remote -control system.

SylvaniaSupersound is featured in three of the 32 new

Sylvania color TV sets. Supersound provides high-fidelity audio with a separate amplifier having bassand treble controls, a high filter switch and a two-wayspeaker system with a 3 -inch tweeter plus a 6 -inchwoofer.

Other features of the line include Automatic

RCA model GC702 25 -inch color console has ChanneLockelectronic tuning (PLL type with crystal control),pushbutton channel selector with LED readout ofchannels and the Automatic ColorTrak System of colorprocessing.

The largest direct -view color picture is on the 26 -inchTrinitron single -gun picture tube. This KV -2643R Sonyconsole has the Alpha chassis and the 14 -button ExpressTuning system.

Sylvania Superset 19 -inch color portable features push-button channel selection, GT-Matic with ASC, GT-300chassis, black -matrix picture tube, room -light monitorand LED channel readout.


The Sylvania VC4000 portable color videocassette recordersystem has 4 -hour capability per cassette with separaterecording and playback sections. Other features include a24 -hour programmable timer for unattended recording, apause button for editing, provision for audio dubbing andpushbutton electronic tuner. The camera is an optionalaccessory.

11fV1I11l IVIII I111:;1,

5

The new Zenith Keyboard Touch -Command channelselector is microprocessor controlled for 105 TV channelswithout setup or fine tuning. No converter is required toreceive special cable channels.

1980 Highlights

Sharpness Control (ASC), GT-Matic color system,Automatic Fine-tuning Control (AFC) and Permatint.

Superset 25 -inch models include two table modelsand 12 consoles. Five have remote controls and allhave GT-Matic with ASC, GT-400 chassis, Dark-Lite50 black -matrix picture tubes, electronic channelselectors, room -light monitors, 6 -inch oval speakersand Cable -Set cable connectors. Seven Superset -Plusconsoles have the previously listed features plusComputer Controller with VIR signal correction anda larger speaker.

Model MQ9014GY 5 -inch monochrome televisionhas internal AM/FM radios, a telescoping antenna,and operates from nine "D" cells or a rechargeablebattery pack. Six consoles and five compact audiosystems also are in the new line.

Four hours of video recording are possible with theVC4000 color videocassette recorder. This portablemachine has separate recording and playbacksections, a pause button, an internal VHF/UHFelectronic tuner and a 24 -hour programmable timerthat turns the recorder on and off for unattendedvideo recording. A battery pack is supplied.

ZenithMicroprocessor control makes possible the Touch -

Command tuning system that provides random anddirect -access to all VHF and UHF channels plus 23cable frequencies without the need for any customersetups. Both on -the -set and remote versions areavailable.

Models in the Royal -Sound series have a built-inauxiliary 10-W amplifier plus two woofers and twotweeters.

Electronic Power Sentry provides electronic voltageregulation that replaces the magnetic/transformerregulation used before. Color sentry includes fiveelectronic circuits that together automatically producea pleasing color picture. System 3 modular chassis isteamed with a 100 degree picture tube having in -lineEFL electron guns.

Five hours of video recording are possible with theVideo Director and L-830 tape cassette. Speed -Searchfunction of the remote control permits a viewing ofunwanted recorded material at about ten timesnormal speed in both forward and reverse modes.Thus sports replays are possible. Stop Action freezesthe tape on one frame for a still picture. The"Weekend" Automatic Timer allows the timer tobegin recording automatically up to three days in thefuture. Touch -Command electronic tuning is pre -tuned for each desired station. A pushbutton givesdirect access to any programmed channel. Anotherunusual feature is the switch for Pulse CodeModulation (PCM) which allows the recording ofaudio with the least noise of any system. A separatedecoder is required for PCM audio playback.


Techniques forrepairing intermittents

By Robert L. Goodman, CET

Repairs of intermittent conditions can be made easier by these examplesand technical tips from an experienced technician.

Most electronic technicians detesttrying to locate the causes of inter-mittent troubles in the equipmentthey service. Troubleshooting symp-toms of erratic operation can betrying and it demands the utmostin knowledge and testing skills.

The proper choice of testingmethods plus factual records ofsimilar defects and their solutionscan be very helpful. That is thepurpose of these case historiesabout known repetitive failures andunique problems.

It doesn't always startIf the sound and picture began

operation when the TV was turnedon, it would continue working untilturned off. But perhaps the nexttime power was applied, therewould be no sound, no raster, anunlighted dial lamp and no voltagein several dc power sources.

In this General Electric YAchassis, most of the dc -voltagesupplies are produced by scanrectification of horizontal -sweeppower. Even the channel -selectorlamp is powered by horizontalsweep.

The usual cause of failure tostart at turn -on is a horizontaloscillator that doesn't oscillate. Onemodule contains the entire circuitand it can be replaced to test forthat possibility.

Horizontal oscillator-'The module

can be repaired if desired. Figure 1shows the oscillator and multivibra-tor circuits. Dc voltage from thephase detector varies the bias ofQ550; and the Miller Effect capaci-tance change operates to vary theoscillator frequency as needed forhorizontal locking. Q550 parallelsthe oscillator coil, L550.

The Q555 transistor operates in amodified Hartley oscillator, with thecollector and base coupling capaci-tor connected to out -of -phase endsof the tapped oscillator coil. Thistype of oscillator has more thanenough feedback and therefore,should start dependably. If it doesnot, some component probably hasa marginal defect. A weak oscillatorwill tend to be erratic aboutstarting.

One handy measure of oscillationstrength is the base -to -emitter volt-age. Photofact 1496-1 shows baseand emitter voltages that calculateto -0.9 V of bias. For an NPNtransistor, this is reverse bias.Stronger oscillation would increasethe negative bias (decrease the posi-tive voltage at the base) and weakeroscillation reverses that action.

Check the oscillator and multivi-brator stages with a scope when theTV is working normally. Thenwhen it fails to start up, check thesame points again, noticing wherethe signal stops.

The components that cause erra-tic starting most often are the 0550

and Q555 transistors, C556 andL550. Be alert for bad solder con-nections and hairline cracks in thecircuit board.

Monostable multivibrator-Transis-tors Q560 and Q570 comprise themonostable multivibrator of Figure1. That kind of multivibrator doesnot oscillate. One of the twopossible states is stable and theother is not. When Q560 is triggeredby an oscillator pulse at the base,the multivibrator goes through onecycle and then stops until triggered,again. The value of a monostablemultivibrator (sometimes called aSchmitt Trigger) is in the precisepulse widths that can be obtained.

For proper operation of thehorizontal -output stage, the widthof pulses at the base of the Q920horizontal buffer must not vary bymore than 10% from the standard.Picture width and horizontal line-arity can be inadequate and thehorizontal -output transistor can failoften if the pulse width is wrong.

Intermittent operation is causedusually by Q560, Q570, diode Y560,capacitor C562 and the L570 choke.

Intermittent heightThe partial schematic in Figure 2

is typical of the vertical -sweepcircuit in many of the older Zeniths(this one is chassis 16Z7C17 ofPhotofact 1105-3).

Many intermittent problems can


Intermittents

DC FROM Q550

PHASE DET HORIZ

REACTANCE

+21V11554

L550

WIHORIZ C554

OSC 100027C556 Q555 =

HORIZ

OSC

.0068 C558

3300

GEOSCILLATOR

- C548

1.041R550

+22 V

330

R562

C550

T027 56K

R556

+21 V

f-.005

9558

390

R560

106

1800

Q560

R563

39001h,

Y560

R570

+22 V -04-",\N--1800

R566

+.4V

C56210K-.4V

.0022

R564

47 K

+220

Q570

GE MONOSTABLE MULTIVIBRATOR

L70 i 11572TO

00`--NAA,-0.-Q920270 HORIZ

BUFFER

C570

1.002

Figure 1 The horizontal oscillator in the GE YA chassis is followed by amonostable multivibrator which provides a constant pulse width to drive thehorizontal -buffer transistor.

C106

.00+58

V5B

VERT OSC

6BA11

11 +10VR233 _34V

C105A

1.0022

8232

2706 R6

VERT HOLD

750K

C105I .0022

V6

C167VERT

11115 6HE5OUTPUT

416 .G11` 6

R114

826

R234

150K

411

- 26 V

` 'OSETUP

SNITCH

ZENITH VERTICAL

R253

336

T2

VERT OUTPUT

Figure 2 Components in the positive -feedback loop of the Zenith tube -typevertical -sweep circuit cause many of the intermittent problems. Thosemarked with arrows are the first suspects.

be traced to the setup switch, whicheliminates the vertical sweep at oneposition by opening the short acrossR253, the cathode resistor. Picturebending and shaded rasters some-times are caused by leakage in thesame switch. Both video and somevertical waveforms are routedthrough the various sections. Testfor an open switch by shortingacross R253.

Other intermittent conditions ori-ginate in components of the posi-tive -feedback network. R115 has

120 VAC

VARISTOR

THERMISTOR

POWER

TRANS

VARYING COLOR

TO

DEGAUSSING

COIL

Figure 3 Symmetrical ac current of themain full -wave bridge is used forautomatic degaussing. At turn -on, thethermistor has about 120Q of re-sistance. A large voltage drop isproduced by the capacitor -chargingcurrent. This higher voltage causes alow resistance in the varistor whichpasses a strong current to the de-gaussing coil. The thermistor wattageproduces internal heat which forcesthe resistance to decrease. This de-creases the thermistor voltage dropand lower voltage is applied to thevaristor. The lower voltage increasesthe varistor's resistance, which re-duces the degaussing current. Theseconditions continue until the thermis-tor is nearly a dead short and the highvaristor resistance blocks the de-gaussing current. The varistor, thethermistor and any of the bridgediodes can cause wrong or intermit-tent degaussing.


produced many cases of wrong fre-quency or intermittent height. Itshould be replaced with one ofhigher wattage. Other suspects in-clude C167, R114, C106 and R233.

Signal -injection tests-Problems inthe positive -feedback network canbe proven by testing the oscillatorand output stages as plain ampli-fiers. Follow this sequence of tests: Disconnect the R114 end ofC 106. If some sort of picture heightremains on the picture tube screen,the vertical -sweep circuit has aparasitic oscillation in the absenceof the positive -feedback pulses.(Normal circuits have no height.)Check filter capacitors, componentsfrom oscillator plate to output grid,diodes around the oscillator cath-ode and the 15K resistor at pin 9. Assemble two clip leads and a0.1 µF capacitor for injection tests. Connect this test capacitor fromthe 6.3 V heater supply to plate(pin 6) of the output tube, whilewatching the raster. If the plate has dc voltage andthe yoke and output transformerare alright, the horizontal line(from the lack of vertical) shouldmove downward and back to thecenter in a fast blink. A very smallamount of deflection should beseen. Move the capacitor lead to thevertical output grid pin 2. About 3to 5 inches of vertical height shouldbe seen if all downstream compo-nents are good. Linearity will bepoor. With the test capacitor moved tothe oscillator plate (pin 11) theheight should be identical to theprevious test. If not, the couplingcapacitor is bad. Connect the test capacitor to thepin 10 oscillator grid. If the tubesand amplifying components of bothstages are not defective, the pictureshould have almost full height(perhaps with poor linearity). Move the test capacitor to thedisconnected end of C106. Theheight should be slightly less thanduring the previous step.

If the last step provided almostfull height, the amplifier path of

the vertical circuit has been checkedand found to be alright. Thereforethe problem of lack of height mustbe in the positive -feedback path.

Intermittent purityAt random periods the color hues

would vary. An intermittent in theautomatic degaussing circuit wassuspected. A test with only the redgun turned on verified the diagno-sis. The degaussing was going intoand,out of operation.

The Figure 3 circuit is typical ofmany, particularly RCA's. An inter-mittently open individual diode inthe bridge or a defective thermistoris the likely cause of the erraticdegaussing. These thermistors oper-ate at a high temperature and oftencrack or develop a loose lead wire.

Also, check the Figure 3 circuitetched wiring for erratic connec-tions.

Zaps output transistorsA General Electric color TV (YA

chassis) occasionally would blow the

horizontal -output transistor whenthe power first was applied. Anintermittent arc was suspected,since the performance was normalat all other times.

The difficulty with testing forsuch arcs is that a large number ofexpensive output transistors can beruined during the unsuccessful tests.

One partial solution is to reducethe input line voltage by means of avariable transformer set for about75 or 80 V. Or a 100 W light bulbcan be temporarily connected inseries with one side of the linevoltage. The bulb gives a visualindication of current. When there isno overload, the bulb is lit withpartial brilliance. If an overloadoccurs, the brightness goes tomaximum.

After the bulb is connected,watch specific areas of the horizon-tal -sweep circuit and around thepicture tube. Look for arcs orsmoke each time the power isapplied.

If the defect can't be located

FROM

HORIZ

BUFFER

Q7O2

HORIZ

OUTPUT

R701

68

Y701

1 DAMPER

BEAD

C7O1

330 pF

0BEAD

Y7O4I

- C7O2'.0056

1.00621

+800 VBOOST

C704

1.10471

TO T710

FLYBACK

GE YA SWEEP A

SUBSTITUTE FOR G702

Figure 4 Those components marked with arrows are likely tohave arcs that can ruin the horizontal -output transistor.

B


Figure 5 This "E" chassis Zenith inter-mittently showed a frequency "hunt-ing" pattern on the screen.

Figure 7 When C258 of Figure 6 wasopen, the B + at terminal T7 had thelarge amount of hash shown by thetop trace. After a new capacitor wasinstalled, the ripple and hash weregone (bottom trace).

FROM

VERT

YOKE

+35V \ R203

4.7-1U4 112

Y

9-92VERTICAL

:L C216

1000 µF

/-

------------,W11 W9 w3,

TO

VERT

YOKE if 600 mA

F203

36V

VERTICAL COLLAPSE

I-` C218I 1000 µF

Figure 8 In the "E" and "F" chassisZenith TVs, these are the points andcomponents to check for sources ofintermittent height.

DC

FROM

PHASE

DET

R807

47K

R805

IM

R809

+24 V

C809

.0015

CR803

C257R811 .0033

270

+65 VR351 R349

1750

10 W ' C258f 10µF

157 MODULE - 50V

R814

180

R816

39+35V

-----MMIMMMal-T1

R818C808 0802 560

10K

C814

T2° PF

TO BASE

DRIVER Q803

DRIFTING HORIZONTAL

Figure 6 Drifting horizontal frequency in the Zenith 25DC57 was caused byan intermittently open capacitor (C258) that was mounted externally to themodule.

Intermittents

within a reasonable length of time,replace these components: Y701damper diode; C701 capacitor; thespecial .0056 C702 capacitor (thisone is critical); boost diode Y704;and boost capacitor C704, as shownin Figure 4.

A transient pulse might becoming from the horizontal buffer.Install a proven buffer module as atest.

Dummy transistor-Another testfor horizontal -sweep overloads thatblow the output transistor is toremove it and substitute the net-work shown in Figure 4B. The hori-zontal sweep will not operate, butthe transistor -drive waveform canbe tested for dangerous spikes andthe collector waveform indicatessome defects (such as a shortedtripler) if it is interpreted correctly.

Perhaps the largest dummy limi-tation is that many arcs and over-loads do not occur unless the sweepand high voltage are normal.

Slowly drifting horizontalIf the horizontal hold of the

25DC57 Zenith was adjusted for

good locking when it was firstturned on, the picture graduallydrifted into the slanted lines ofwrong oscillator frequency. Or ifthe hold was adjusted correctlyafter it was warm, the horizontalwas out -of -lock next time powerwas applied.

At other times, the picture wouldhave a violent "hunting" pattern(see Figure 5) that resulted fromovercorrection of the frequencyerror. These various symptoms wereintermittent and at other times theoperation was normal.

The AFC and oscillator circuitswere on the 9-57 module; therefore,the module was replaced. However,the troubles continued erratically.

The search was widened toinclude the B+ sources and thehorizontal components not on themodule (schematic in Figure 6).Nothing wrong was found untilmodule terminal T7 was scoped.Hash was present there (top wave-form of Figure 7) at times. Whenthe problem disappeared on itsown, the hash was gone, as shownby the lower scope trace.

Paralleling a new 10 yF capacitor


across C258 stopped the problem,and it was soldered into place afterthe old one was removed. Therewas no horizontal drift followingthe capacitor replacement.

Causes of similar horizontal drifthave been traced to the L214oscillator coil (which also is thehold control) or to C257, the .0033pF tuning capacitor for the oscilla-tor coil.

Intermittent vertical sweepA picture that collapsed to a

narrow horizontal line was a prob-lem that occurred several times invarious chassis of the "E" and "F"Zenith color receivers. Sometimesthe line then would black outbecause of the safety circuit actionthat applies cutoff bias to thepicture tube whenever there is novertical sweep. The 0.6 A verticalfuse also might blow.

Vertical sweep in these modularTVs requires one -35 V supply andone +35 V supply. Figure 8 showsthe yoke terminals and dc supplyterminals of the vertical module.

Either bad filter capacitors orintermittent opens at the U2 andW3 pins can cause these intermit-tent symptoms. Carefully check theback side of the chassis whereterminals are inserted, and resolderany suspicious -looking joints.

Scope the +35 V and -35 Vsupplies at U2 and W3 for exces-sive ripple or hash. If abnormalamplitudes are found, check for anopen C216 or C218 filter capacitor.

If the filters or the terminalsbecome intermittent for very long,the ripple and hash will ruin theyoke or blow the 0.6 A fuse. Some-times one of the power outputtransistors is damaged also.

General tipsThe only difference between a

regular defect and intermittenttrouble is that the intermittentproblem has symptoms only atcertain times. If the intermittent

can be made to malfunction con-stantly, the cause can be found byconventional methods.

Some intermittent problems canbe triggered by vibration, shock ortemperature changes. Therefore,they all should be tried in anattempt to control the intermittent.

These are some techniques to try: Use a variable line -voltage trans-former to supply 10 V above or 10V below the rating. Experiment todetermine if there is a criticalvoltage. Flex the circuit boards and theirconnectors. If moving the entireboard promotes some disturbance,check, clean or tighten the plug-insprings and connectors. Tap gently at specific compo-nents on the suspected module. Prywith a non-metallic rod or screw-driver. Heat the suspected area with aninfra -red lamp or heated blower.Don't use excessive heat; it's notnecessary and it might cause dam-age. Canned coolant should be sprayedcarefully and selectively on compo-nents in the suspected area. Varythe amount of cooling; often only asmall decrease of temperature isbest. After the problem area has beenpinpointed, use a strong light and amagnifier to locate small cracks insolder connections or board wiring.A crack that can't be seen with theunaided eye can open a circuit orcause an intermittent connection. Acircular crack around a pin or aneyelet is the source of many erraticproblems. After the joint is solderedand repaired, look at it again withthe magnifier. Some joints do nottin properly, and extra care mustbe used.

Use any or all of these techniquesto control the beginning or endingof the intermittent period. After thesymptoms can be controlled, theactual defect can be found with nomore than the usual trouble.

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A meter that liedA dim, narrow, out -of -focus and

unstable picture was on the TVreceiver screen. During some initialtests, the technician noticed thetube cathodes didn't seem to glowas brightly as usual. The tubeheaters were series -connected andthe 21LU8 socket was easy toreach, so the tech measured the acvoltage across those heater pins.About 22 volts ac was the VOMreading.

As that was a normal reading, hewent on to other tests. After sometime, the technician decided tocheck the heater voltage a secondtime. This time the meter indicatedzero volts. The meter was notdefective or intermittent; it mea-sured the line voltage correctly andwas not erratic.

After a few minutes of perplexity

By Wayne Lemons, CET

over the TV problem and themysterious meter readings, the tech-nician thought of the answer toboth.

DC versus ACThis TV had an instant -on

circuit which, when the power wasswitched off, connected a diode inseries with the tube heaters to keepthem warm at half voltage. There-fore, all heaters were to be suppliedwith ac voltage when the powerswitch was on, or with half -waveunfiltered dc voltage during power -off operation.

When he first measured theheater voltage, the tech (correctly)used the ac -voltage function be-cause the power was turned on. Inthat VOM, a single series -connecteddiode rectifies the ac by passing

DIODE

120VAC TUBES

1

FALSE READINGS

AC MEIER

120V

AC METER

only one peak, and the rangeresistor is chosen so the meteraccurately reads the RMS value ofthe ac voltages.

A double on/off switch was usedin this TV model. When turned on,one section applied ac to thelow -voltage power supply. The othersection shorted across the heaterdiode to restore proper heatervoltage.

The diode -shorting section wasopen, therefore, the TV had normalB+ voltages but only half the usualheater voltage. The original TVsymptoms were caused by the lowheater voltage, not by weak tubes.

Meter polarityThe diagram shows both possible

connections for testing the heatervoltage at the diode cathode. Withthe leads connected as shown bythe top VOM, both diodes had thesame polarity, and the current pathwas not changed significantly. Nor-mally, the meter operated only fromthe positive peak of any ac voltage.Therefore, it provided the samereading for the positive half -wavedc as it did for ac.

When the technician reversed themeter leads (which is permissiblewith ac), the two diodes (see bottomVOM diagram) had opposing polar-ities, thus opening the current pathand giving a zero reading.

Other readingsThere are possibilities for wrong

readings with other meters orconditions. If the tech had used theVOM jack that adds a couplingcapacitor (for checking ac in anac/dc mixture), both polarities ofmeter probes would have providedlow readings of the half -wave dcheater voltage. Also, a VTVMwould have given a low reading ofthe half -wave dc voltage, regardlessof the polarity.


test euuípment YIJPfl

Pocket CricketSencore has introduced a pocket -

sized transistor tester. Battery -oper-ated, the Pocket Cricket is designedto check nearly all transistors and

FETs either in or out of circuit.An automatic circuit turns the

instrument off after 10 minutes ofuse to save batteries. The unit canbe ac -operated on the bench withan optional PA208 power adapter.


Benchtop DMMA 31/2 -digit benchtop digital multi -

meter can measure ac or dccurrents up to 20 A. Model 1351from Data Precision has 0.10/o basicaccuracy. Featuring 34 ranges, itcan measure dc volts from + 100pV to 1200 V, ac volts from 100 uVto 1000 V RMS and resistance from100 Mc to 20 M S2 with either highor low voltage. Measurements aredisplayed on a 0.43 -inch LED dis-play. Model 1351 is complete withtest leads and spare fuse and ispriced at $199.


Debounce switchCincinnati Electrosystems' model

395 Debounce Switch provides amethod for clocking logic circuits

without contact bounce. A push-button switch generates a choice ofa positive or negative 10 ps pulse ora level change.

The instrument is priced at $7.95.Circle (22) on Reply Card

Digital multimeterModel LM -353 31/2 -digit digital

Volksmeter from Non -Linear Sys-tems is packaged in a 1.9"x2.7"x4"plastic case. Basic functions includeac and dc volts, ohms, and ac anddc mA. Full-scale ranges are 1, 10,100 and 1000 V, 1, 10, 100, 1000

V.kO.mA1.

HI MODEL LM -353 1CI VAC VDC kmO

K10 MRACmA mLO DCmA

I4etOf

and 10,0001000 mA.

Low -power ohms provide in -cir-cuit tests of resistive components.The unit utilizes an LCD display.Replaceable AAA size batteriesallow up to 100 hours of operation.The LM -353 sells for $149.50.


kn and 1, 10, 100 and

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uroduct: MilShort form catalog

A condensed catalog describing aline of instrumentation for measure-ment, analysis and/or recording ofpower -system parameters is avail-able from Dranetz Engineering Lab-oratories. Each product section listsfeatures, gives a comprehensivedescription of the instrument andplug -ins and includes a photograph.Detailed specifications are alsolisted.


Replacement partsOver 65 hard -to -find IC audio

amplifiers have been stocked at GEauthorized distributors as replace-ments for such popular types as AN214, TA7205P, UPC1025H and HA -1306.


Microcomputer systemsRadio Shack has introduced the

TRS-80 Model II, microcomputersystem. Software is available forgeneral ledger, accounts receivable,

inventory control, mailing list man-agement and payroll. Model II has abuilt-in 12 -inch high -resolution videomonitor that displays 24 lines of 80normal characters or 40 expandedcharacters.


Condenser microphoneShure Brothers' model SM81 car-

dioid condenser microphone fea-tures flat frequency response, goodsignal-to-noise ratio and smoothcardioid pattern at all frequencies.In addition, the electronics sectionhas low total harmonic and inter -modulation distortion. The SM81

also features a 3 -position low -frequency response switch locatedon the microphone case.

User net price is $225.Circle (38) on Reply Card

WooferAcoustic Fiber Sound Systems has

introduced the Model 0006, 4"x10"woofer. The unit offers 50-5000 Hzfrequency response with 30W powerhandling capability.


Tuner/timer for VCRsThe TU-41AU tuner/timer from

US JVC is designed to give owners ofportable VCR units the capability ofrecording television programming ata predesignated time within an eightday period. The unit has a built-inelectronic digital timer for precise

scheduling, a channel lock button toprevent accidental channel changeduring recording and a 12 -buttonelectronic tuner. It can receivechannels 2 through 13 on VHF, andchannels 14 through 83 on UHF.


Record cleanerRecord Sweep from Robin Indus-

tries incorporates a quick -fill cov-ered reservoir which feeds metered

amounts of moisture to a velvetcleaning surface. Individual fibersloosen and pick up accumulateddust particles from grooves. Sug-gested retail price is $3.35.


toolA desoldering tool that is refill-

able is available from Tech -WickTool. A transparent plastic capsnaps off for reloading, and each

refill contains approximately 20 ftof pure copper stranded wick. Thetool sells for $7.50, which includes arefill in any of three sizes.


Portable radioZenith's Trans -Oceanic R-7000

portable radio has 12 -bands consis-ting of seven shortwave bands cov-ering all used frequencies from 1.8MHz to 30 MHz, AM broadcastingband, FM broadcasting band, long -wave FAA weather band, aircraftcommunications band and publicservice band. The radio is priced at$379.95.



catibosOO1flI

New England Business Serviceoffers an 80 -page full -color (3039)catalog describing more than 300business forms, service tickets, re-pair tags, and many other items toimprove the image and efficiency ofbusinesses.


ORA Electronics has available a1979 Winter Catalog featuringhundreds of replacement parts in-cluding ICs, transistors, FETs,electrolytic capacitors, tool kits,hardware packs and test cassettesthat help in repairs of Japanese andeastern electronic products.


Heath Company has available a96 -page catalog describing kits forcolor TVs, hi-fi components, digitalclocks, personal computers, testequipment and many accessories.One new item is a 35 -MHz dual -trace delayed -sweep scope.


Mallory-A 112 -page general cat-alog presents thousands of electron-ic components. Featured are addi-tions to existing lines as well as newproducts not previously availablefrom Mallory.


General Electric-A new and ex-panded 416 -page edition of the Gen-eral Electric Replacement Semicon-ductors Guide features expandedcoverage of both the PRO and MROlines and provides an indexed listingof GE replacement entertainmentsemiconductors. Cross reference ismade to various OEM as well asuniversal replacement by JEDECnumbers.


Simpson-A 60 -page, 4 -color cat-alog lists the complete SimpsonElectric Company line of stockanalog and digital panel meters,meter relays, controllers and testinstruments. Catalog 4900 includesSimpson's model 463 compact liquidcrystal digital multimeter and the#00758 universal temperature adap-ter probe.


Quam-Nichols-12-page Catalog'79 lists 150 different speakers. Thecatalog also includes updated list-ings of general purpose, automotive,music instrument, communications,high fidelity and commercial soundspeakers.


ITT Components offers a 33 -pagecapacitor catalog that includesrating charts, performance curves,and application notes for eachseries of solid -tantalum capacitors.


Association of Audio -VisualTechnicians-The Annotated Di-rectory of Parts and Services forAudio -Visual Equipment, lists thesources of parts and services formore than 1,000 brands of audio-visual equipment. The equipment islisted by brand names and sourcesof parts and present distributorsare listed. Price of the directory is$20 plus $2 postage and handling, ifpayment does not accompany theorder.


Electronic ServicingAdvertising Sales Offices

NATIONAL SALES MANAGER/CHICAGOJim Reilly, 1011 E. Touhy Ave., Suite 245,Des Plaines, IL 60018;Phone: (312) 299-2601

KANSAS CITY, MISSOURIHelen Hull, P.O. Box 12901,Overland Park, KS 66212;Phone: (913) 888-4664

NEW YORK, NEW YORKJoe Concert, One Penn Plaza, Suite 2532,New York, NY 10001;Phone: (212) 564-8454

FT. LAUDERDALE, FLORIDABrinker and Brinker2240 N.E. 53 StreetFt. Lauderdale, FL 33308Phone: (305) 771-0064

SAN FRANCISCO, CALIFORNIAJohn MacKay, 703 Market St., Room 1109,San Francisco, CA 94103Phone: (415),546-1040

LONDON, ENGLANDJohn Ashcralt d Co., 12 Bear St.,Leicester Square, London, WC2H 7AS,England; Phone: 930-0525

AMSTERDAM, HOLLANDJohn Ashcralt & Co., John J. Lucassen,Sloterweg 303, 1171 VC-Badhoevedorp,Hol land;Phone: 2968-6226

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

Make America smarter.Give to the college

of your choice.

Council for Financial Ad to Education. Inc.ME 680 Fifth Avenue, New York, N Y 10019

M E A Public Service of This MagazineA. The Advertising Council.

IT'S NO PUZZLE TO ORDER

OELRICH SERVICE FORMSFOR TV -RADIO a 2 WAY RADIO SERVICE LEGAL FORMS FOR CALIF. FLA.UTAH NOW AT YOUR PARTS JOBBER 3H WRITE FOR CATALOG 864

OELRICH PUBLICATIONS4040 N. NASHVILLE AVE. CHICAGO. ILLINOIS 50634


NEW CATALOG OFHARD-TO.FIND

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Lists more than 2000 items: pliers, tweezers,wire shippers, vacuum systems, relay tools, op!tical equipment tool kits and cases. Send foryour free copy today!

JENSEN TOOLS AND ALLOYS1230 SOUTh pRiEST DRIVE TEMpE, ARIZONA 85281



limarketulaceAdvertising rates in the Classified Section are 35cents per word, each insertion, and must beaccompanied by cash to insure publication.Each initial or abbreviation counts a full word.Minimum classified charge $3.00.For ads on which replies are sent to us forforwarding (blind ads), there is an additionalcharge of $3.00 per insertion to cover departmentnumber, processing of replies, and mailing costs.Classified columns are not open to advertising ofany products regularly produced by manufac-turers unless used and no longer owned by themanufacturer or a distributor.

For SaleT.V. SALES & SERVICE SHOP in central NewJersey. Located on main hwy. 19 years grossed$110,000.00 1978. Zenith franchised dealer.Unlimited potential. Owner moving. Write inconfidence to: Electronic Servicing, P.O. Box12901, Dept. 521, Overland Park, KS 66219.

6-79-31

ESTABLISHED SHOP in 5 -town retirement area,business good, overhead low. Owner wants tosemi -retire. Terms. Dave Haspany, Bentonville,Arkansas 72712. 6-79-21

ALA'S SPRAYCANS CAN BE REFILLED! Coldfreeze, tuner wash, lubricants, etc., go from$3.00 to 60 cents. I will send you directions andinformation on the refilling procedure, thechemicals, where to buy, how much to pay. Send$25.00. You won't be sorry. Solidstate, 3832 W.Lisbon, Milwaukee, WI 53208. 4-79-4t

AM RADIO reception for interiors of buildings,ships, etc. Catalog. EXTRONIX, 64 Gough,Ivyland, PA 18974. 5-79-6t

REPLACEMENT COLOR YOKES-DEALER ONLY.Zenith 95-2501-2532-2638-2667-S-89633 etc.$19.94, Magnavox 361380-1 $21.95, Sylvania, GEetc. $17.95 to $22.95. Request for price list onyour letterhead. David Sims Enterprises, Inc., 665Jericho Turnpike, Huntington Station, N.Y.11746, (516) 549-3925. 5-79-tf

TECH BENCH kit or plans. Designed for the TV/Radio Tech. Test instrument shelf on two powercolumns with 10 fused outlets. Bench has fourfused outlets with C-MOS grounding, four largetool drawers and neon bench lighting. E -Z buildconstruction. Plans and kit information $1.98plus 50 cents handling. Technical Workshop, Box368, Placentia, CA 92670. 5-79-3t

AUTOMOBILE RADIO and tape replacementparts: Delco, Chrysler, Philco-Ford, Motorola,Panasonic and many others. Large inventory.Laran Electronics, Inc., 3768 Boston Road,Bronx, NY 10469, (212) 881-9600, out of New YorkState, (800) 223-8314. 5-79-tf

TV & RADIO TUBES, 36 cents EA!! Free colorcatalog. Cornell, 4221 University, San Diego,California 92104. 8-76-tf

ELECTRONIC SURPLUS: CLOSEOUTS, LIQUIDA-TIONS! Parts, equipment stereo, industrial,educational. Amazing values! Fascinating itemsunavailable in stores or catalogs anywhere.Unusual FREE catalog. ETCO-011, Box 762,Plattsburgh, N.Y. 12901. 6-78-tf

SOUTH LAKE TAHOE-Television and appliancestore. Well established. '79 gross over $300,000.By owner (702) 588-6662. 6-79-2t

SAVE HUNDREDS: American Made quality Head -Ends, V/V, U/V Converters, Camera Modulators.Mid -bend available. Factory Prices. Also smallCATV System amplifiers. Send $5.00 (or letter-head). Box 809, Boynton Beach, Fla. 33435.

5 -79 -EOM

TV SERVICE VALENCIA, CA. 25 miles NW of LAin the Santa Clarita Valley. Excellent location fastgrowing area. A REAL buy at $4,950.00 and fiveyear lease on the building. Owner wants to retire.W.E. Kent, 25508 Via Dolarita, Valencia, CA.91355. (805) 255-0345 7-79-1t

COLOR PICTURE TUBE REBUILDING EQUIP-MENT. Semi automatic electronically controlledprocess. Complete training. Call or write AtollTelevision, 6425 W. Irving Park, Chicago, IL60634. Phone 312-545-6667. 7-79-31

SAMS PHOTOFACTS FOR SALE. 19 drawers,last number 1451 for $1200.000 Sold out shop.Schuls Radio TV Service 524 N. Cherry St.Valentine, Neb. 69201 7-79-1t

Business OpportunityMEN/WOMEN FOR FUN! Shaklee IndependentWholesale Distributors earn $200-$5,000 monthly,Bonus, New Car, Etc. Details, Golden, RT2, Box392ES, Fair Grove, MO 65648 Phone (1-417)759-2738. 3-79-121

WANTED FOR CASH! We buy scrap electronicparts containing gold, silver, platinum! Immedi-ate top dollar cash offer by return mail. Ship to:American Metals Co., P.O. Box 30009, Dept. ES,St. Andrews Branch, Charleston, SC 29407.

11-78-íf

TUNER TECH NEEDED. Must be top notch andcapable of management. Call toll free 1-800-433-7124 (In Texas call 1-800-772-7411) between 5 and6 pm central lime. 7-79-2t

"NEED EXPERIENCED professionals in largeaerospace conglomerate. Degree required. Manybenefits. Excellent future. Send name, address,employer, phone, and best time to contact to:"Roy W. Randall 8433 S.E. Banyan Tree St. HobeSound, FL 33455 7-79-1t

Advertising ServicesTERRIFIC SWAP OFFERS NATIONWIDE! Next 5issues $2. "Electronics Trader," Box 73 -ES, FollyBeach, SC 29439. 1-79-tf

WISDOM is...givingto theMarchofDimes

Birth defectsare forever.

Unless you help.THIS SPACE CONTRIBUTED BY THE PUBLISHER

advertisers' b1ia

American Audio 5

Dictaphone Corp. 27

Dielectric Communications ...1

Fuji-Svea Enterprise 7

Gamit Enterprises, Inc. 39

General Electric Co., TubeProducts Dept. IBC

Jensen Tools and Alloys ....43

Master Appliance Corp 7

NATESA 41

NESDA 39

Oelrich Publications 43

PTS Electronics ..13, 15, 17, 19

GTE Sylvania-ECG/CR ... IFC

Zenith Radio Corp. BC

rHelp!Anytime you havea question aboutyour subscription toElectronic Servicing,please Include amailing label to In-sure prompt serviceon your inquiry.

Change ofAddressIf you're about tomove, please let usknow approximatelyfour weeks beforethe move comesabout. Simply affixyour present labelhere, and carefullyprint the updated in-formation below.

I Please Help Us to

Electronic ServicingP.O. Box 12901Overland Park, KS 66212

Serve You Better

AFFIXLABELHERE

I Name

I Employer(Please Print)

Address

LCityZip -


IF YOU DUYENOUGH OF THESE...

GENERAL ELECTRIC WILLGIVE YOU AN AWARD

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See your General Electric Distributortoday if you haven't received complete detailsabout our all -new "pro plus" Award Program.

Remember: you earn "pro plus" points

Irncral Electric Company. 1979

Ir

for GE semiconductor bags, tripler box tops andGE receiving tube flaps. And, if you should finda GE monogram sticker in one of the bags, it'sworth an extra 20 "pro plus" points!*

*Mix cash and points for bigger prizes. Full details in Monthly Bulletins once you enroll.

WE'RE AT YOUR SERVICE.Tube Products Department-Owensboro, Kentucky 42301

GENERAL

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ELECTRIC _1Pro Plus Headquarters

P.O. Box 6863 Chicago. Illinois 60680

FOR YOUR OWNREPUTATION

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AL -WAYS INSIST ON.._...__.

EXACT REPLACEMENTPARTS AND ACCESSORIES

Zenith's Instant Parts Program (ZIP) is thesimplest, least expensive Zenith inventorycontrol system ever devised for TV servicetechnicians. Organizes the most needed, mostused Zenith TV replacement parts and acces-sories so they are where you want them,when you want them.

And ZIP keeps these parts organized thruperiodic checks by your Zenith distributor

salesman who replaces slow moving stocknumbers with new, more popular parts. As aresult, your original investment is protected and,'our supply of Zenith parts remains current.

And you need never again risk your reou-:ation with "will fits"

Call your Zenith distributor now for all:he details on the ZIP program that best suitsyour individual needs.

ZENITH RADIO CORPORATION/SERVICE PARTS & ACCESSORIES DIVISION11000 Seymour Avenue /Fra-<lin Park, Illinois 60131


SYLVANIA HELPS...(.courtesy of RCA), a trip to Nogales, Mexico courtesy of Hiser Publications and a...

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Transcript of SYLVANIA HELPS...(.courtesy of RCA), a trip to Nogales, Mexico courtesy of Hiser Publications and a...