A HOWARD W. SAMS PUBLICATION Curing Horizontal ......2SA 436 2.50 2SA 816.70 2SC 281.59 2SC 763.59...

EiectronicJuly, 1978

A HOWARD W. SAMS PUBLICATION

CuringHorizontal

OscillatorDrift

$2.25

Sylvania Chroma

Digital Toggles

Betamax Chroma

Pricing Philosophy

Tibor Komoroczv,Service Manager

Howard Roach TV & Appliance300 East Valley Blvd.

San Gabriel, CA 91776

Bottomslip

9iit throw away that GE tube flapnd lose award points. Get yourBottoms Up Catalog and win!"

Your reputation is our reputationTube Products Department Owensboro, Kentucky 42311

July, 1978 E Volume 28, No. 7

Electronic Servicing,

Contents

14 Curing Horizontal OscillatorDrift, Part 1-Tips for locat-ing defective parts and makingstabilizing adjustments for thecathode -coupled multivibratoroscillator are discussed. Othertypes will be covered nextmonth-Wayne Lemons.

page 14

20 The Basics Of Industrial .Electronics, Part 13-The versatile 555timer IC is described as a clock oscillator. Also, one way to toggleJ -K flip flops is illustrated-J.A. "Sam" Wilson.

26 Service Management Seminar, Part 7-If you are reluctant tobegin the higher rates you know you should charge, then you needall of the facts plus a "philosophy of pricing."-Dick Glass.

30 Servicing Sylvania Color TV, Part 6-Chroma functions of the E44chassis are explained in detail, including identification of the ICpins according to those functions-Gill Grieshaber.

38 Sam Wilson's Technical Notebook-A pulse of signal leaves thematerial with some magnetism, which can be "read" as a logic 1,by proper methods. Also discussed are facts about diode recoverytime, and the protection of series diodes-J.A. "Sam" Wilson.

45 Servicing Betamax Videotape Recorders, Part 3-Both the typicalmethods and the specific Betamax circuits for recording chromaare presented-Harry Kybett.

About the Cover-These pictures illustrate some visual symptoms ofwrong horizontal -oscillator frequency or phase. Photography by CarlBabcoke, with the graphic design by Mary Christoph.

DEPARTMENTS

4 Electronic Scanner6 Symcure7 Troubleshooting Tips8 Service Associations

11 Reader's Exchange48 Product Report

49 Antenna Systems50 Audio Systems51 Test Equipment52 The Marketplace52 Advertisers' Index

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

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

urgent.Other phone answeringmachines only take calls.Ours calls you.

Dictaphone announces asystem that not only recordsmessages, but calls you anddelivers them.

It's our new Ansafone 696telephone answering system.

After it records a message,it will ring any number you tell itto - including a beeper ser-vice, if you have one.

Ansafone 696 means younever need to miss an urgentcall - no matter where you are.

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 71P

Mail to: Dictaphone Corporation105 Oak StreetNorwood, New Jersey 07648

Dictaphone and Ansafone are trademarks of DictaphoneCorporation, Rye, NY IES-078

July, 1978Circle (2) on Reply Card

1

You can be suremore times in more circuits in more places

than with any other multimeters on the market today

Each Sencore DVM is backed with 15 Megohm input Impedance forone third less circuit loading on every measurement. That means50% higher accuracy than other DVMs.

DVM38 $39531/2 DIGIT .1% DCV ACCURACYAUTO -RANGING DVMA "prime" standard at your fingertips formeasurements you can trust. Auto -rangingfor extended low-level range and ease ofoperation. 15 Megohm input impedanceassures .1% reading accuracy is maintainedin solid state circuits. Highly sensitive, yetfully protected to 2000 VDC overloads. Hi -Lo Power Ohms circuit simplifies in -circuitresistance measurements.

DVM37 Nev" $26831/2 DIGIT .1% DCV ACCURACYPORTABLE DVMPrime standard .1% accuracy on the benchor in the field' for less than $250. TheDVM37 is the most accurate portable DVMyou can buy, with 15 Megohm input imped-ance for 50% more accuracy. Includes auto-matic features-Auto Zero, Polarity, Deci-mal, Overrange. Fully protected inside toover 2000V on all functions, includingOhms, and protected outside with super -rugged case. Full ranges for every test.Fingertip "Push -On" switch in probe savesbatteries as power is applied only whenneeded.

New DVM37

DVM32

In stock at your favorite localSencore Full Line Distributor.

DVM32 $22531/2 DIGIT .5% DCV ACCURACYPORTABLE DIGITAL MULTIMETERBench and field master for digital accuracymeasurements anywhere. 0.5% DCV accur-acy, backed with 15 Megohm input imped-ance. Exclusive battery -saving Auto -Displayturns the display on automatically when youmake a measurement. 2000V input protect-ion on all functions and ranges-includingOhms.

DVM36 $1583'/z DIGIT .5% DCV ACCURACYPOCKET PORTABLE DVMPocket portable lab accurate performancethat fits every budget with highest perform-ance -to -price benefits of any meter..5% DCVaccuracy, backed with 15 Megohm input im-pedance for lowest circuit loading. Full pro-tection to 1000 V on all functions andranges-including ohms. Drop -proof case.Battery -saving "Push On" button in probe.

DVM35 $1343 DIGIT 1% DCV ACCURACYPOCKET PORTABLE DVMFast, direct reading digital accuracy for theman on the go. Same features as DVM36,except 3 -digit, 1% DCV accuracy, backedby 15 Megohm input impedance that is tentimes more accurate than analog meters.

DVM36SENCO1=tDIGITAL MULTIMETER SPECIALISTS3200 Sencore Or ,Sioux Falls,S0 57107 (605)339-0100

Electronic Servicing

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

EDITORIAL

CARL H. BABCOKE, Editor

MICHAEL SCHEIBACH, Managing Editor

DUDLEY ROSE, Art Director

HILLARY MANES, Editorial AssistantMARY CHRISTOPH, Graphic Designer

EDITORIAL ADVISORY BOARD

LES NELSON, ChairmanHoward W. Sams & Co., Indianapolis

JOE A. GROVES, -Technical ConsultantHoward W. Sams & Co., Indianapolis

CIRCULATION

JOHN C. ARNST, Director

EVELYN ROGERS, Manager

0 r 0

ABPe. 10

Member, American Business Press

Member, Audit Bureau of Circulations

ADMINISTRATION

GEORGE H. SEFEROVICH, President

GEORGE LAUGHEAD, Publisher

ADVERTISING SALES

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

Phone: (913) 888-4664

MARILYN CARROLL, Production

Regional and Advertising Sales Officeswith Advertising Index

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

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

Subscription prices to qualified subscribers:1 year -58.00, 2 years-$13.00, in the USAand its possessions. All other foreigncountries: 1 year-$11.00, 2 years-$19.00.Subscription prices to all others: 1 year-$25.00, 2 years-$50.00, in the USA and itspossessions. All other foreign countries: 1

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

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

Circle (3) on Reply Card2 ELECTRONIC SERVICING

AVAILABLE NOW ! ONLY $ 5.90Add 61.00 postage and handling

JAPANESE TRANSISTOR SUBSTITUTION MANUALAn invaluable Japanese to Japanesesubstitution guide for appromixately3000 transistors.

Covers the 2SA, 2SB. 2SC, and2SD series.

Introduction includes a guideto understanding Japanesetransistors.

A 90 page, SU:" by 11", softcover book.

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Seeking Original Japanese Replacement Parts for CB, TV and Stereo Repair Use?

2SA2SA 492SA 522SA 532SA 702SA 1012SA 1022SA 2342SA 2352SA 2402SA 3292SA 342

.59

.59.59

1.10.45.59.59

1.00.90.70.90

2SA 7442SA 745R2SA 7472SA 7482SA 7502SA 7552SA 7562SA 7582SA 7642SA 7652SA 7742SA 7772SA 794A2SA 798

4.904.905.801.00.59

1.603.705.804.404.90.59

1.001.00.70

2SB 5372SB 5392SB 5412SB 5542S8 5562SB 5572SB 56102SB 5642SB 5952SB 5962S8 600

1.604.904.40

10.004.903.40.70.70

1.901.607.00

2SC 6962SC 7082SC 7102SC 7112SC 7122SC 7172SC 7272SC 7302SC 7312SC 7322SC 7332SC 7342SC 7352SC 738

1.951.90.45.45.59.59

1.904.405.80.59.59.59.59.59

2SC 11152SC 11162SC 1116A2SC 11242SC 11272SC 11612SC 11622SC 11662SC 11672SC 1170132SC 117202SC 11732SC 11752SC 1177

4.404.906.601.301.401.901.00

.596.606.608.50.90.90

14.00

2SC 16752SC 16782SC 16792SC 16812SC 16822SC 16842SC 16872SC 16882SC 17082SC 17282SC 17302SC 17562SC 17602SC 1765

.592.254.25

.70.45.59.70.70.59

1.90.59

1.401.908.80

2SD 3132SD 3142SD 3152SD 3252SD 3302SD 3412SD 3502SD 3522S13 35602SD 357D250 3582SD 3592S0 3602SD 361

1.101.201.201.101.005.605.90.90

1.101.001.301.001.201.00

HA 1156HA 1158HA 1159HA 1196HA 1197HA 1201HA 1202HA 1211HA 1306WHA 1322HA 1339HA 1339AHA 1342ALA 1111P

3.005.305.804.903.901.502.251.503.704.404.404.404.402.50

TA 78012MTA 78012PTA 78015MTA 78015PTBA 810 SHTC 5080PTC 5081PTC 5082TO 3505APUHIC 002

'

UHIC 004UHIC 005UPC 20C

6.605.806.505.803.705.803.403.908.505.80

5.805.804.40

2SC2SC 183 .592SA 353 .70 2SA 814 1.90 2SC 756 2.80 2SC 1189 1.20 2SC 1775 .45 2SD 370 3.00 LA 1201 2.50 UPC 41C 3.70

2SA 377 2.00 2SA 815 1.00 2SC 184 .59 256 756A 3.00 2SC 1209 .70 2SC 1816 3.90 2S0 3715 2.80 LA 1364 4.40 UPC 554C 2.802SA 436 2.50 2SA 816 .70 2SC 281 .59 2SC 763 .59 2SC 1211D .59 2SC 1846 .70 2SD 380 7.60 LA 3300 3.00 UPC 555H 2.252SA 440 .90 2SA 818 1.30 2SC 283 .59 2SC 772 .45 2SC 1212A 1.40 2SC 1885 .70 250 381 1.41i LA 3301 3.00 UPC 563 3.702SA 473 .70 2SA 837 2.80 2SC 284 1.20 2SC 773 .70 2SC 1213 .70 2SC 1908 .59 2SD 382 1.4G LA 4030P 3.40 UPC 566H 1.602SA 483 3.00 2SA 839 2.15 2SC 317 1.20 2SC 774 2.00 2SC 1215 .70 2SC 1909 3.90 2SD 388 3.40 LA 4031P 3.00 UPC 576 3.702SA 484 2.50 2SA 841 .59 2SC 352A 2.50 2SC 775 1.95 2SC 1222 .45 2SC 1913 1.20 2SD 388A 4.40 LA 4032P 3.40 UPC 577H 2.252SA 485 2.00 2SA 847 .59 2SC 353A 2.50 2SC 776 2.65 2SC 1226A .90 2SC 1945 5.60 2SD 389 .90 LA 4051P 3.70 UPC 592HZ 1.602SA 489 1.60 2SA 850 .59 2SC 367 .90 2SC 777 3.50 2SC 1237 2.25 2SC 1951 1.10 2SD 390 1.00 LA 4400 3.70 UPC 1001H 4.902SA 490 .90 2SA 872A .59 2SC 369 .59 2SC 778 3.60 2SC 1239 3.90 2SC 1957 1.20 2SD 421 8.50 LD 3120 2.50 UPC 1008C 7.002SA 493 .59 2SA 885 .70 2SC 371 .59 2SC 781 2.65 2SC 1279 .70 2SC 1969 4.90 no 424 8.50 M51513L 4.90 UPC 1016C 3.002SA 495 .45 2SA 908 11.00 2SC 372 .45 2SC 783R 3.60 2SC 1306 2.90 2SC 1973 1.10 no 425 6.50 M5152L 2.50 upc 1020H 3.702SA 496 1.10 2SA 913 1.20 2SC 373 .45 2SC 784 .59 2SC 1307 3.90 2SC 1974 1.90 2SD 426 4.60 M51841P 2.80 UPC 1025 3.402SA 497 1.60 2SC 374 .59 2SC 785 .59 2SC 1310 .59 2SC 1975 4.40 2SD 427 3.00 M5320P 2.25 UPC 1026C 3.70

2S B2SA 505 1.20 2SC 377 .70 2SC 789 1.00 2SC 1312 .59 2SC 2028 .90 2SD 525 1.60 M53273P 2.80 UPC 1032 2.252SA 509 .70 2SC 380 .59 2SC 790 1.40 2SC 13136 .59 2SC 2029 3.90 no 526 1.10 M53274P 2.50 UPC 1152H 3.402SA 525 .70 2SB 22 .59 2SC 381 .59 2SC 793 2.80 2SC 1316 8.50 2SC 2074 1.90 2S0 555A 6.60 M53393 7.60 UPC 1156 3.002SA 530 1.30 2S0 54 .59 2SC 382 .59 2SC 799 3.60 2SC 1317 .45 2SC 2076 .59 no 610 1.90 M54730 P 8.802SA 537A 2.25 2SB 55 .59 2SC 383 .90 2SC 802 3.60 2SC 1318 .45 2SC 2091 2.80 MPS U31 1.902SA 539 .59 2Se 75 .45 2SC 387A .59 2SC 815 .59 2SC 1325A 7.60 2SC 2092 3.90 SG 6131tv) 5.95 STK 011 7.60 uPD 858C 9.50,2SA 545 .59 2SB 77 .45 2SC 388A 1.00 2SC 828 .45 2SC 1327 .59 2SC 2098 4.90 STK 014 9.50 PLL 01A 8.802SA 561 .59 2SB 173 .45 2SC 394 .59 2SC 829 .45 2SC 1330 .70 F ET STK 015 6.60 PLL 02A 8.802SA 562 .59 2SB 175 .45 2SC 403 .59 2SC 830H 5.90 2SC 1335 .70 2SD STK 016 8.50 SN 7400 .19'2SA 564A .59 2SB 176 .45 2SC 430 .90 2SC 838 .59 2SC 1342 .59 2SK 19BL .90 STK 022 11.00 SN 7490 .602SA 565 1.10 2SB 178 .70 2SC 454 .59 2SC 839 .59 2SC 1344 .59 2S0 16 5.90 2SK 23 1.10 STK 032 14.002SA 5662SA 606

3.401.60

2SB 18625B 187

.45

.452SC 4582SC 460

.59

.592SC 8532SC 867

.904.25

2SC 1345132SC 1346

.59

.702S0 282S0 72

2.501.10

2SK 302SK 33

.701.10

STK 435STK 439

8.5011.00

DIODES2SA 607 1.60 2SB 202 1.60 2SC 461 .59 2SC 870 .59 2SC 1347 .70 2SD 75 .90 2SK 34 1.10 STK 502 8.80 78L0 1.10.2SA 624 1.10 2SB 220 .70 2SC 478 1.10 2SC 871 .59 2SC 1358 5.90 2SD 77 .59 2SK 40 .70 STK 503 9.60 S 84 .602SA 627 3.60 2SB 303 .59 2SC 481 1.60 2SC 895 4.90 2SC 1359 .59 2SD 81 3.00 2SK 41 1.10 TA 7027M 3.70 S 188 .252SA 628 .59 2S6 324 .70 2SC 482 1.50 2SC 891 3.40 2SC 1360 1.00 2SD 90 1.60 2SK 49 1.30 TA 7045M 3.00 S 332 .452SA 634 .70 2SB 337 1.60 2SC 484 1.60 2SC 898 4.40 2SC 1362 .59 2SD 91 1.60 2SK 55 1.30 TA 7054P 2.50 S 953 .252SA 640 .59 2S8 346 .70 2SC 485 1.60 2SC 900 .45 2SC 1364 .70 2SD 92 1.90 2SK 61 1.40 TA 7055P 3.00 S 1007 .452SA 642 .70 2SB 367 1.50 2SC 486 1.60 2SC 923 .45 2SC 1377 4.90 2S0 93 2.80 25K 68 1.30 TA 7060P 1.60 S 1209 .452SA 643 .70 2SB 368B 2.15 2SC 493 3.90 2SC 929 .45 2SC 1383 .59 2SD 118 4.40 3SK 22Y 2.55 TA 7061AP 1.90 S 1211 .452SA 653 2.80 2SB 379 1.10 2SC 495 .90 2SC 930 .45 2SC 1384 .59 2SD 130 1.20 3SK 35 2.25 TA 7062P 1.90 S 1555 .252SA 659 .59 2S8 381 .59 2SC 496 .90 2SC 941 .59 2SC 1396 .70 2SD 141 1.40 3SK 37 3.00 TA 7063P 1.60 S 1588 .252SA 661 .70 2SB 400 .59 2SC 497 1.60 2SC 943 .70 2SC 1398 1.10 2S0 142 2.00 3SK 39 2.25 TA 7064P 1.90 S 1885 .252SA 663 4.90 2SB 405 .59 2SC 509 .70 2SC 945 .45 2SC 1400 .59 2S0 143 2.80 3SK 40 2.25 TA 7066P 2.00 S 2076 .252SA 666 .70 2S6 407 1.40 2SC 515A 1.40 2SC 959 1.50 2SC 1402 4.90 2SD 178 1.10 3SK 41 2.50 TA 7074P 4.90 S 2093 .452SA 671 1.40 2S6 415 .59 2SC 517 3.95 2SC 971 1.00 2SC 1403 4.90 2SD 180 2.50 3SK 45 2.50 TA 7075P 4.90 S 2473 .252SA 672 .70 2SB 434 1.20 2SC 535 .59 2SC 982 .90 2SC 1407 .90 2SD 187 .59 3SK 48 5.90 TA 7076P 4.90 N 34 .252SA 673 .70 2SB 435 1.40 2SC 536 .59 2SC 983 1.00 2SC 1419 1.10 2S0 188 3.00 3SK 49 2.50 TA 7089P 3.00 N 60 .252SA 678 .70 2SB 440 .59 2SC 537 .59 2SC 984 .90 2SC 1444 2.80 no 201 3.40 TA 7102 5.80 OM .402SA 679 4.90 2SB 449 1.60 2SC 538A .70 2SC 994 3.90 2SC 1445 3.00 2SD 202 3.90 MK 10 2.00 TA 7106P 4.90 0010 .602SA 680 4.90 2S8 461 1.20 2SC 562 .70 2SC 996 3.40 2SC 1447 1.60 250 204 1.40 TA 7108P 1.90 VO 68 .40

IC2SA 682 1.50 2SB 463 1.20 2SC 563 1.10 2SC 1000BL .59 2SC 1448 1.60 no 205 1.40 TA 7109P 3.40 'VO 6C .402SA 683 .70 2SB 471 1.60 2SC 605 .70 2SC 1012 1.50 2SC 1449 1.00 2SD 213 5.90 TA 7120P 1.902SA 684 .70 2SB 473 1.20 2SC 619 .59 2SC 1013 1.10 2SC 1451 2.25 2SD 217 4.40 AN 203 2.50 TA 7122AP 1.90 ZENER DIODES2SA 695 .70 2SB 474 1.00 2SC 620 .59 2SC 1014 1.10 2SC 1454 5.60 2SD 218 4.40 AN 214Q 3.00 TA 7124P 1.602SA 697 .70 2SB 481 1.20 2SC 627 2.25 2SC 1017 1.40 2SC 1475 1.40 2S0 220 2.50 AN 217 1.90 TA 7129P 1.90 WZ 050 .452SA 699A .90 2SB 492 1.00 2SC 631 .90 2SC 1018 1.20 2SC 1478S .70 2S0 223 1.90 AN 239 7.00 TA 7130P 2.80 WZ 052 .452SA 705 .70 2SB 507 1.60 2SC 632A .45 2SC 1030C 2.80 2SC 1509 1.10 2SD 224 1.90 AN 247 4.40 TA 7136P 1.30 WZ 061 .452SA 706 1.60 2SB 509 1.60 2SC 634A .59 2SC 1047 .70 2SC 1567 1.10 2SD 226A 1.60 AN 274 3.40 TA 7146P 4.20 WZ 071 .452SA 715 1.40 2SB 511 1.10 2SC 642A 5.90 2SC 1051 4.40 2SC 1567A 1.10 2SD 227 .45 AN 2776 2.40 TA 7150P 4.40 WZ 075 452SA 719 .59 2S0 514 1.90 2SC 644 .45 2SC 1060 1.40 2SC 1584 8.50 2SD 234 1.00 AN 315 3.00 TA 7159P 2.50 WZ 081 452SA 720 .59 250 523 1.00 2SC 645 .70 2SC 1061 1.40 2SC 1586 7.60 2SD 235 1.00 AN 328 3.90 TA 7200P 4.60 WZ 192 .452SA 721 .59 2S6 526C 1.30 2SC 650 1.30 2SC 1078 39.00 2SC 1624 1.30 2S0 236 1.60 AN 362 3.00 TA 7201P 4.60 WZ 260 452SA 725 .59 2SB 527 1.60 2SC 665H 8.50 2SC 1079 5.90 2SC 1626 1.10 2SD 255 1.60 BA 511 2.90 TA 7203P 3.70 WZ 280 452SA 726 .59 '2S6 528D 1.60 2SC 668 .45 2SC 1080 4.40 2SC 1628 1.30 2S0 261 .60 BA 521 2.90 TA 7204P 3.402SA 733 .59 2S8 529 .90 2SC 680 2.80 2SC 1096 1.00 2SC 1647 1.00 2S0 287 3.70 HA 1137 4.90 TA 7205P 2.902SA 738 .70 2SB 530 4.40 2SC 681A 5.80 2SC 1098 1.10 2SC.1667 3.40 no 288 1.40 HA 1138 4.40 TA 7310P 3.952SA 740 2.65 2SB 531 3.40 2SC 684 1.10 2SC 1111 3.40 2SC 1669 1.60 2SD 291 2.80 HA 1149 5.60 TA 78005M 5.802SA 743A 1.60 2SB 536 1.60 2SC 693B .59 2SC 1114 3.70 2SC 1674 .59 2SD 300 5.60 HA 1151 4.40 TA 78005P 5.80

PRICES MAY CHANGE WITHOUT NOTICE COD ORDERS WELCOMED

Minimum order $5.00 Ohio residents add 4% sales tax. Add $1.00 postage and handlingQuantity discount prices. Ask For Our Complete Price List. Mfg. inquiries VVelcomerl

All parts guaranteed against factory defect

IMMEDIATE DELIVERYWITHIN 48 HOURS

TOLL FREE TELEPHONE FUJI-SVEA ENTERPRISENationwide 800,543-1607 Local 5131874-0220Ohio 800/582-1630 874-0223

Hours: Mon. thru Fri. 10-7 Sat. 11-5

a division of Fun-Svea IncorporatedDept. E/S

P.O.BOX 40325 CINCINNATI, OHIO 45240TELEX -21-4732

Circle (4) on Reply CardJuly, 1978 3

MpIrtscanuernews of he ndus ry

Introduced by Abbott Laboratories is a microprocessor -controlled analyzer thatdetects serum hepatitis in blood intended for transfusions. As reported inElectronics, the analysis detects the color changes of blood samples when they aremixed with enzymes of certain kinds. A photometer which is sensitive to two lightcolors measures the light coming through the liquids in a test tube, and the micro-processor changes the signal to absorbance units, prints out the test results, andmarks those containing the hepatitis antigen. Used with the microprocessor are avoltage -to -frequency converter, and a counter -timer.

Analog primary field telephones soon will be replaced by digital phones in the U.S.Air Force. Tests of the 25 samples show several advantages, such as: the ability tohandle conference calls; four levels of priority, including an override for urgentmessages; and no degradation of voice quality over long distances. According to anarticle in Electronics, the Tri-Tac phone system uses Continuously -Variable -SlopeDelta Modulation (CVSD) that is non -synchronous. To prevent phase inversions, adiphase type of modulation is used during transmission; then for reception, themodulation is stripped away. The ICs have a combination of I2L and CMOS logicfor low power drain.

Ford Motors has an automated optical -inspection unit on the production line.Optical sensors connected to a microcomputer automatically measure the axle gearratio of 21,000 axles per day. Electronics described the unit, and commented thatthis is a trivial job for a sophisticated microcomputer, but additional automation isplanned. Eventually, the system will determine the model of car for each axle, fillaxles with the proper level of grease, and measure the dimensions of brake drums.A laser engraver makes metal tags that will be placed on axles listing the modelnumber, axle ratio, the manufacturing date, and the shift.

RCA ColorTrak TVs for 1979 have ChannelLock, a frequency -synthesis tuningsystem with crystal control that eliminates any need for fine tuning on AFT. Thetuning system is said to be available in 27 models.

The "System 3" color -TV line from Zenith has six major and three minor modulesthat contain most of the circuitry. Even the high -voltage components are on amodule; only the large power -supply parts are located on the chassis. The Zenithservice department states that no soldering is required to replace any module orother large component, including the power transformer. This design shouldminimize any need for bench repairs.

Sony offers a subscription microfiche service for all Sony parts. A package of 184" x 6" microfiche cards replaces 3,726 pages of printed material. The cardscontain the part number, description, available substitutions, price to the servicer,and retail list price. A new packet of 18 cards will be mailed each month tomaintain a continuous update, and the price to Sony dealers and authorizedservice agencies is $4 per month.

Total United States market sales of color television receivers to dealers increasedby 21.0% in April, 1978 compared with the same month last year andmonochrome sales increased 7.8% according to the EIA.

4 ELECTRONIC SERVICING

Anyonecan be replaced.

SEMICON TORREPLACEMENTGUIDE

AND CATALOG FORHOME ENTERTAINMENT

EQUIPMENT

Raytheon did it.We just made it easier for you to replace

more than 100,000 semiconductors. We did itby replacing the old RE number system witheasier -to -use, universal REN numbers.

Now all 362 different types (including 67new types) of our semiconductors for homeentertainment service are at your fingertipsfaster. Without the fuss and bother of cross-referencing numbers. Our new numbering

system exactly corresponds to the one most often used by the serviceindustry. Best of all for you, our streamlined product line meets 95% ofyour service needs.

But that's all we changed. Using this new red book still opens theway to all of Raytheon's famous advantages. Highest quality. Highestavailability. Immediate delivery.

Our new replacement guide and a new inventory starter kit,REN-K2494, are immediately available at your Raytheon distributor.Get this coupon to your distributor, or directly to us. Raytheon Com-pany, Distributor Products Division, Fourth Avenue, Burlington, MA01803.617/272-6400.

Rush me a copy of your new Raytheonsemiconductor replacement guide.

I presently use Raytheon semis.I am not presently using Raytheon semis.I want more info on the REN-K2494 Starter Kit.

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Circle (5) on Reply CardJuly, 1978 5

VON I Symptoms and curescompiled from field reportsof recurring troubles

Chassis-Admiral 9M50PHOTOFACT-1694-1

OPENM600

II

+122V--1.---WeI

R909 1 +76V>>-ir.- TO

SOURCE 820 II 06045W

Symptom-No high voltageCure-Check R909, and replace if open. Also checkT600 and Q604 for damage

Chassis-General Electric 19JAPHOTOFACT-1328-2

HORIZ0206 OUTPUT

Y208 / N R254

56K

C234 .057 C236.0047 T 1600T,

_ DEFECTIVE

Symptom-Dark picture, screen controls don't workCure-Check the components marked by arrows, andreplace if bad

Chassis-Magnavox T952PHOTOFACT-1293-1

9KX6V104

3-9

VIDEOOUTPUT

REDUCED

R132/'

6800

TO DRIVECONTROLSAND CRT

R131

+290V

L31

Symptom-Dark picture, screen controls operateokayCure-Check resistor R132, and replace if reduced invalue

Chassis-RCA CTC40PHOTO FACT -111-3

PULSES R174FROM

T11 #11 105W

HORIZ LINC146

.18 R175

4700 C228TO

/11.54jFHV ADJUSTDEFECTIVE

Symptom-No high voltage, hot odorCure-Check yoke capacitor C228, and replace it ifdefective

ti

Chassis-RCA CTC38PHOTOFACT-1000-3

6GH8A 8188V13A

5600 To X1911=11 R16A X20

I 3000CRT

AND X21

HORIZ R190 BIASBLANK

re 8200REDUCED

Symptom-Picture is too brightCure-Check resistor R190, and replace it if reducedin value

Chassis-Zenith 14DC15PHOTOFACT-1363-2

TO OSCHORIZ

C303 I HOLD

.0011

R3676800

L226 C304

/.0047LEAKY

6U10 V209C

DISCHARGE

R372100K

Symptom-Narrow picture, too bright, no horiz.lockingCure-Check C304, and replace it if leaking


troubleshootinen

No top convergenceZenith 14Z8C50(Photofact 1106-3)

During a preliminary diagnosis inthe customer's home, the color -TVperformance seemed to be normal,except for the bad picture tube.After the picture tube was replacedin the shop, all of the purity andconvergence adjustments were pro-ceeding as usual, until I reachedthe vertical "top" adjustments.None of these three controls hadany effect.

From past troubleshooting ex-periences, I knew which conver-gence components can cause such aproblem. Unfortunately, none ofthem were bad. Next, I reasonedthat if the convergence componentswere okay, then the defect must bein the AC signal voltages. In thiscase, all three controls are supposedto obtain a signal from the cathodecircuit of the 6HE5 vertical -outputtube.

DC voltages of the 6HE5 wereabout right, so I dragged out thescope to check the waveforms.

VERT OUTPUT

6HE56

-8.81N

2

4 -II20. 5V

BLUE

sr

RE

470Q

2W

390V18/

12 mld

(Waveform analysis is not oftenhelpful with convergence problems,except as here where the drivingsignal might be bad or missing.)

When C7 was disconnected, thepulses at the cathode changed tosawteeth, but the convergencedidn't return. Disconnecting C97made no change.

After working for too long with-out any success, I finally remem-bered that these Zenith terminalstrips give more trouble than the

actual components do. I discon-nected all of the wires and compo-nents from the terminal strip that'scommon to C96, C7, and R137. I

connected them together at the nextpoint of the circuit, and the con-vergence operated normally. Re-turning to the empty lug of theterminal strip, I measured a 1,000 -ohm short to ground.

Defects are where you find them,and some occur in the wiring andelectrical connections. This terminalstrip is not shown on the schematic.

Phillip M. Jones, CETMartinsville, Virginia

Lightning damageGeneral Electric 190B(Photofact 1471-1)

According to the customer, hewas watching the TV when light-ning struck nearby, and at thatinstant the TV lost both sound andpicture. This seemed to be aroutine repair to replace the com-ponents usually zapped by lightningtransients.

First, I checked F401 and Y400power -supply diode, finding (as ex-pected) that the fuse was open andthe diode was shorted. However, theTV refused to operate after theseparts were replaced.

The power supply voltages testedokay until I reached the 22.3 -voltsupply (and the others obtainedfrom it). This supply originates asB+ from rectified horizontal sweep,followed by a transistor regulator.These facts and symptoms pointedtoward a loss of horizontal sweep.

No pulses were found at theanode of Y402, the 29.8 -volt scan

rectifier. Tracing back from thehorizontal output, I could find nohorizontal signals anywhere, even at

continued on page 8

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troubleshootintacontinued from page 7

the Q203 horizontal oscillator.Q203 had proper collector voltage,and a quick in -circuit check provedthe transistor was not open orshorted. L202 and the emittercomponents also measured okay.

Finally, I replaced Q203, justbecause there was little else to do.You guessed it; with the newtransistor, the horizontal remaineddead.

This called for a serious study of

the circuit, and I noticed that theQ203 emitter drove the base ofQ205. When I checked Q205, Ifound the base/emitter junction tobe open, and a new transistorbrought back normal operation.

How about one open B/E junc-tion killing the entire TV? Evident-ly, the lightning spike had blownQ205 also.

Carroll L. HudsonDozier, Alabama

service RDR rNATESA Convention

August 24 through 27 are thedays selected for the 1978 NationalAssociation of Television & Electron-ic Servicers of America (NATESA)convention, to be held at the GreatChateau Louise Resort, Dundee,Illinois (near Chicago's O'Hare Air-port).

Sessions for association businesswill form the center of the conven-tion, but other activities won't beneglected. One panel will discussindustry problems and solutions;another panel is scheduled to con-sider the problems brought by newtechnologies. Seminars and theNATESA Certification Test will beoffered to technicians. Other know-ledge can be gained from fellowservicers and industry leaders, whowill be present. Also scheduled areevents for relaxation and entertain-ment. These include a golf tourney,a banquet with floor show, a sing -along, and an encore appearanceby Art Hoist (a dynamic humorist),who will appear August 26 bycourtesy of RCA.

For more details, contact:NATESA, 5908 South Troy Street,Chicago, Illinois 60629.

NESDA/ISCET ConventionsThe "City of Roses" (Portland,

Oregon) is host to the 1978 conven-tions of the National ElectronicService Dealers Association (NESDA)and the International Society ofCertified Electronic Technicians(ISCET). Participating also in theAugust 7 through 13 conventions arethe Washington State ElectronicsCouncil (WSEC) and the Oregon Pro-

fessional Electronics Association(OPEA).

Preliminary plans call for a golftourney, a Forest Belt scope work-shop, and a NESDA executive coun-cil meeting on August 8. Wednesdayactivities include a Business -Management School, technical sem-inars, and an ISCET ServiceabilityInspection. Thursday, August 10,has schedules for a NESDA nomina-tions meeting, the large trade show,CET and CSM tests, and the ISCETannual meeting. Convention eventsfor Friday include the NationalService Conference, the NESDAannual meeting and election ofofficers, and the Zenith annualdance. Saturday is to bring anotherNESDA meeting, all -day ISCET tech-nical seminars, The Electronics Hallof Fame banquet, and the installa-tion of NESDA officers. Sundayevents (August 13) include theannual ISCET breakfast and instal-lation of officers, and the NESDAexecutive council meeting.

During the August 9 dinner, RCAwill present Art Hoist, who was thehit of the San Antonio conventions.

Candidates for NESDA officersinclude Robert "Bob" Villont forpresident and Warren Baker forvice president. Announced ISCETcandidates are: for chairman, LarrySteckler, and Jesse B. Leach, Jr.;for vice-chairman, Forest H. Belt,and Walter R. Cooke.

For more convention informationcontact: NESDA, 1715 Expo Lane,Indianapolis, Indiana 46224, or:ISCET, 3101/2 Main, Ames, Iowa50010.

winlexchame

There is no charge for listing in Reader's Exchange, butwe reserve the right to edit all copy. If you can help witha request, write direct to the reader, not to ElectronicServicing.

For Sale: New B&K-Precision 1977B TV Analyst (usedonly once), complete with manual, cables, slides, andextra set of tubes. Cost $493, will sell for $325, ormake offer. Gerald L. McKouen, 534 Pacific, Lansing,Michigan 48910.

For Sale: Obsolete tubes. Send a list of your needs.Also B&K-Precision tube tester model 707 for $50.Needs some work. Elmwood TV, 136 Market Square,Newington, Connecticut 06111.

For Sale: Sencore DVM-32, $100; B&K-Precision 1076Analyst, $165; Heathkit post/market sweep generator,factory wired, in mint condition, $125. John R. Zanath,1809 Grant, Aliquippa, Pennsylvania 15001.

For Sale or Trade: Superior Instrument TW11portable tube checker with wood core and roll chart,$35; Precision tube checker counter model 911 meterwith roll chart, series 915, $45; RCA color -bargenerator WR64B, like new, $75; and Cornell DubilierBF90 capacitor checker, $35. Need Rider's RadioManuals, or what have you. Troch's Television -radio-appliances, 290 Main, Spotswood, New Jersey 08884.

For Sale: 1 RCA WR-52A stereo -FM simulator; 1 RCAWR-69A TV/FM sweep generator;1 RCA WV -76A highsensitivity AC VTVM; 1 RCA WV -98C VTVM; 1

B&K-Precision model 282 digital multimeter. Bestoffers. Debra Garcia, Spinks TV Sales & Service, 823Madeline Court, Baton Rouge, Louisiana 70815.

Needed: A schematic and service manual for a PhaseCorporation Medford audio -sweep generator, modelASG-200, and a packard Bell Telecaster, model 900.Will buy, or copy and return. Martin Winkler, 6618St. Clair, North Hollywood, California 91606.

Needed: A CRT for Tektronix 531A scope (partnumber 154-0757-00). Send condition of CRT andprice. Mike Murphy, 40512 Regency Drive, SterlingHeights, Michigan 48078.

For Sale: A CK3000 Sylvania test jig with manuals and57 adapters; Sencore YF33 Ringer; Heath IT5230 CRTTester; IG57A sweep/marker generator, IG28 dot/color generator; Polaris HV probe; EMC model 213tube tester; one tube caddy with 132 most -used tubes;also, many other audio instruments and meters. MikeMurphy, 40512 Regency Drive, Sterling Heights,Michigan 48078.

For Sale: Duplicate material from my library of earlyradio and TV service literature. Factory material,data, Rider's manuals, etc. Lawrence Beitman, Box46, Highland Park, Illinois 60035.

For Sale: B&K-Precision 1077B TV Analyst, $250; andHeathkit post-marker/sweep-generator, $100. AllenRose, 650 Daphne, Broomfield, Colorado 80020.

For Sale: B&K-Precision dual -trace 10 -MHz model1470 triggered scope, with one PR 20 10:1/directprobe and one PR 152 demodulator probe, $300. Also,B&K-Precision 520B transistor tester with FP -5Dyna-Flex probe, $95. Both like new, used only a fewhours. Richard Lopez, 9916 Franklin, Glenn Dale,Maryland 20769.

For Sale: Heath CO -1015 ignition analyzer (5 -inchCRT), with 12 VDC power inverter, $95; and JudWilliams curve tracer, $55 (new in box.) Richard A.Miller, 3909 Marion Drive, Enon, Ohio 45323.

For Sale: Rider's Troubleshooter's Manual, volumes1 through 19, with index; also, Rider's manual forrecorder changers and recorders. Arthur F. Wilhelm,Art's Radio & TV, Rural Route #1, Box 15,Mascoutah, Illinois 62258.

For Sale: Precision scope model ES 500, and sweepgenerator model E 400, all leads and manuals, inperfect condition, both for $125. Also, remote controlunit model 9K-1 for Fisher 400c Master Audio Control,and BB54-A storage battery. Al Crispo, 159-30-90Street, Howard Beach, New York 11414.

Needed: University 312 tweeter speaker HF 206 andrear housing. H. D. Stevens, 31 Second Street, No.Arlington, New Jersey 07032.

Needed: Low-cost B&K-Precision model 11075 Analyst.Need not be working. Lowell L. Vonada, VonadaRadio & TV, Park & Fifth, Lincoln, Kansas 67455.

For Sale: EICO 369 sweep and marker generator, withcables and manual, $85; measurements model 80standard signal generator, with manual, $300; both inperfect condition. W. J. Budzyna, 49 Gill Court,Whitinsville, Massachusetts 01588.

Needed: Roll chart for Hickok tube tester, model 534.(For old 4 -prong tubes). Need an adapter #C40 forB&K-Precision CRT tester 440, adapter to test12CWP4, if available. Elmer L. Mosley, 720 Poplar,Kenova, West Virginia 25530.

Needed: RCA Service Notes 1923-1928, 1929-1930, and1931-1932. Manual/Schematic for Tektronix 511ADscope. 1. A. Call, 1876 East 2990 South, Salt Lake City,Utah 84106.

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

continued on page 12

July, 197811

ilexchanuecontinued from page 11

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

For Sale: Bell & Howell (Heathkit) digital rrultimeter,like new, $25 plus postage. Robert M. Dorman, 1917Ridge Lake Drive, Chesterfield, Missouri 63617.

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

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

For Sale: B&K-Precision sweep/marker generatormodel 415, with leads, never used-in carton, $350plus shipping. Channel Electronics, Route 206, And-over, New Jersey 07812.

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For Sale: Sencore PS148 oscilloscope/vectorscope,excellent condition, $150. Johnnie L. Jones, RR 2, Box140, Shelbyville, Missouri 63469.

Needed: Schematic and parts list for Herbrandtach-and-dwell meter (manufactured by Utica -Her -brand division of Kelsey Hayes), model HT -864. Xeroxcopy is okay. Send price COD. Otis M. Cowart, P.O.Box 987, Vero Beach, Florida 32960.

For Sale: Nine years of Electronic Servicing; CIEelectronic course leading to FCC license; Knight RFand sweep generators, 5 -inch scope, RC boxes, signaltracer. Make offer. Epperson, Star Route B, Satsuma,Florida 32089.

Needed: Schematic for Pennscrest model 8400 guitaramplifier. Will buy, pay for copy, or copy and return.Steven C. Martin, Route 2, Box 85C, Rutherglen,Virginia 22546.

Needed: Schematic and instruction book for aUnimatics model XL -1 automatic TV camera. Will buy,or copy and return. Victor Scheideler, 2381 HammsRoad, Burlington, Wisconsin 53105.

Needed: Schematic and service manual (especially foralignment) for an Arlington radio series A2 -MB andchassis number 42 '400401. Will pay, or copy andreturn. Oris Hippe, 12109 West Washington, WestAllis, Wisconsin 53214.

in the Nation's Capital.The greater Washington area gets

Capital gains, with Winegard.From Georgetown to Alexandria,

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and throughout the District of Co-lumbia, you'll find Winegard prod-ucts hard at work bringing viewersgood TV reception. In fact, there isWinegard equipment in 200 -year -oldtownhouses, in some of the newestfederal buildings, on college cam-puses, in high rise apartments, inembassies, servicemens' barracks,police headquarters, fire stationsand residential homes.

The Washington area is prettyhilly, and like other parts of the na-tion, TV "ghosts" present a problem.That's one reason installers rely onmedium or larger Winegard outdoor

antennas. Not because of weak sig-nals, but to cut down or eliminate"ghosting': .. a benefit of Winegard'sattention to high front -to -back ratioand sharp directivity in its antennaengineering.

On the other hand, many peoplein the area want to pull in the weakerBaltimore stations, some 60 and moremiles away. They use Winegard highgain antennas and preamps to givegood, clear, long distance receptionand a bigger selection of programs.

Retail TV set stores need top-notchpictures on their showroom receivers,

too, and many of the leaders rely onWinegard TV systems to do the job.In turn, they recommend WinegardTV reception products to their setcustomers.

This most important city in theworld, Washington, is also one morecity in the U.S. where Winegard isat work providing the finest TV re-ception in a variety of situations.

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WINEGARD WORKS... Everywhere!

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Para rnSs datos marque (8) en la tarjeta.

July, 197813

CuringHorizontal

Oscillator Drift,

By Wayne Lemons, CET

Control Or Oscillator?A customer complains

TV requires perhaps a dozenadjustments of the horizontal holdduring each evening. However, whenyou examine the TV and try thehorizontal -hold control, the lockingis normally tight. Which stage hasthe problem?

Another TV receiver is reportedto jump out of horizontal lock everytime the program changes fromnetwork to local, or from local tonetwork. Where is the defect?

These two common symptomsillustrate the dilemma of every TVtechnician. Of course, it's likely theproblem is in the sync, powersupply, or horizontal -oscillator cir-cuits. But, the analysis of horizontallocking is complicated by the twofunctions of the oscillator. Theoscillator circuit itself can cause awrong frequency. In addition, eachoscillator has a control circuit thatvaries the oscillator frequency sothe sweep is in step with the picturefrom the station. This controlcircuit often is called the AutomaticPhase Control (APC) or the Auto-matic Frequency and Phase Control(AFPC). I favor the AFPC acronym,because it makes clear that boththe frequency and phase of the

Part IMost cases of intermittent locking or driftinghorizontal frequency originate in TV receivers thathave tubes. Therefore, this article is directedprincipally to tube circuits. However, after a fewlogical modifications, the methods apply to solid-stateequipment as well.

oscillator signal are controlled. (Atthis time, the sync signal is groupedwith the AFPC operation, becausethe quality or amplitude of the syncsignal can't affect the frequencyvery much.)

Either or both of these basic cir-cuits can cause wrong horizontal-oscffiator frequency, loss of locking,or intermittent locking. The ques-tion is this: WHICH of these twocircuits has the defect?

Divide And ConquerBriefly stated, the method that

locates these trouble spots more

The combinationof slanting barsand one uprightbar indicates anunstable oscilla-tor frequencythat's varying be-tween about 120Hz too low, andcorrect frequencyof the wrongphase.

rapidly than others is to disconnectall possible components (or wholecircuits) while maintaining enoughoscillator operation to keep apicture showing on the screen.We'll supply specific details as weproceed. But, for starters, youshould disable any components thatare included only for stability ornoise immunity. Also, disconnectthe entire AFPC circuit as a checkof the free -running oscillator fre-quency.

Of course, you must know whichcomponents can be disconnected ordisabled. That is why we will

14ELECTRONIC SERVICING

220pF

47pF

SYNC

180K

70V PP

6V

STABILIZINGCOIL

+ 270V

330pF

560

HORIZONTAL OSCILLATORBROADMOOR 6911CPHOTOFACT 1113-2

8FQ7

HORIZ OSC

6 + 195V

-14V 7

500K

HORIZ HOLD

+ 270V

2.2K 470pF

001200V PPOUTPUT

Figure 1

describe the operation and testingof several types of horizontal cir-cuits.

M ultivibrator WithRinging Coil

One circuit that was very popularwith many B&W TVs (and a fewcolor sets) is the cathode -coupledmultivibrator oscillator, with a ring-ing coil for better noise immunityand stability (see Figure 1).

This type of circuit is one of theeasiest to adjust and troubleshoot.One reason for the uncomplicatedservicing is that the AFPC voltage

typically measures around zero.Thus, it can be grounded toeliminate any possibility that adefect in the AFPC circuit mightforce the oscillator frequency out oftolerance. After the AFPC is dis-abled by the ground, the oscillatoralone can be tested for frequency orfor drift.

Ground The GridMost oscillator circuits that re-

semble the one in Figure 1 canhave the AFPC operation disabledby a ground attached to the multivi-brator grid at pin 2. The following

Upward slant ofbars on the TVscreen prove theoscillator is run-ning too slow,and the 7 barsshow the error isabout 420 Hz.

instructions allow the method to beused with even more TV models.

If the horizontal can be made tolock at all, measure the range ofDC voltages at pin 2 of the 8FQ7oscillator tube as you vary the holdcontrol as much as possible withoutlosing the locking. (Typically, thesecircuits show one or two volts ofvariation before locking is lost.)Adjust the hold control at thecenter of the locking range, andmeasure the DC voltage at the grid.If the voltage is between +1 and+2 volts, then connect a 11/2 -voltflashlight battery with the positivetoward the grid and the otherterminal grounded.

However, if the grid voltagemeasures less than +1 volts at thecenter of the locking range, merelyground the grid. In either case, theoscillator should continue to oper-ate (later, we'll discuss the steps totake if it quits), and the frequencythat results determines our nextstep.

Examine the picture. An uprightpicture that drifts slowly to eitherside indicates a correct horizontalfrequency, but one that's not locked.Sometimes, this is called "zerobeat," and it's the ideal condition.However, such perfect frequencywithout locking is very rare.


July, 1978 15

Horizontalcontinued from page 15

Probably, the picture will consistof several (or many) diagonal bars.These bars are the horizontalblanking pulses between the pic-tures that are slanted because ofthe non -synchronized scanning fre-quency. These diagonal stripes orbars are useful, for the number ofthem indicates the frequency error.Each diagonal stripe represents afrequency error of 60 Hz. There-fore, you can count them, multiplyby 60, and obtain the approximatefrequency error in Hertz.

Further, you can know whetherthe oscillator is running fast orslow. When the bars are lower atthe left and higher at the right ofthe picture, the frequency is toolow. (Imagine that scanning beamgoing up hill, and being slowed bythe pull.) Bars that are higher atthe left and lower at the right showa frequency that's too fast. (Thebeam is coasting faster downhill.)

Analyze The DriftAfter the AFPC control voltage

has been clamped or grounded,usually one of two conditions willbe seen: either the frequency will benearly correct (zero beat, or two tothree bars), or it will changedrastically (a parasitic double -trig-gering, or many stripes). Tests ofthe almost -correct frequency are

given next; the radical changes willbe discussed a bit later.

Just a few stripesAfter the AFPC control voltage

has been grounded or clamped andthe free -running frequency is notfar from being correct, then adjustthe horizontal -hold control for zerobeat (or as near as possible,considering the lack of locking).Operate the TV for 15 to 30minutes, and look at the pictureevery minute or so to see the extentof the frequency drift. Monitor thedrift by counting the number ofdiagonal stripes. All of these cir-cuits drift in frequency; you mustdetermine whether the amount ofdrift is normal or not.

Normal drift perhaps is two orthree stripes. But after you havedone this series of tests severaltimes, you'll know how many toexpect. Of course, you want theleast variation of the number ofstripes, since that indicates lessdrift.

that the symptom (be-fore the ground eliminated theAFPC voltage) was excessive driftwhich caused frequent loss ofhorizontal hold, but that the fre-quency drift was normally smallafter the AFPC voltage was re-moved, then the defect is in the

Downward slant of the bars indicates a too -fast frequency,and the many bars show a frequency error of about 1140Hz.

AFPC circuit, and not in theoscillator. AFPC tests will be givenlater.

Oscillator driftAt the other extreme, when the

AFPC was eliminated by the groundor the clamping, if the oscillatordrift was excessive, then a defect inthe oscillator circuit is indicated.

Each oscillator circuit has one setof components that primarily deter-mine the frequency. Each of thecircuits shown this month estab-lishes the frequency by a resistance/capacitance (RC) network versusthe amplitude of signal at the RCnetwork. Other models have LCtuned circuits, and signal ampli-tude plays a smaller role in thefrequency. This is a good reasonwhy we are giving specific tips foreach model.

No PictureIn cases where grounding or

clamping the AFPC DC voltageresults in a loss of high voltage andpicture, there are two generalpossibilities. Perhaps an oscillator defect ischanging the frequency enough toeliminate the high voltage. How-ever, before the AFPC action wasdefeated, misadjustments of thehold control and ringing coil might

This highly unstable oscillator condition is called "double -triggering," "parasitic -oscillation," or "Christmas -Tree"

operation.


warp the frequency enough topermit some imperfect operation. Perhaps this particular circuitcan't be operated with the outputDC voltage of the AFPC shortedout. Solid-state circuits, and a fewtube circuits, often bring a fixedamount of DC voltage in throughthe AFPC. Probably the extra DCvoltage is used for bias; and if so,the oscillator can't function withoutit. Check your schematic carefully.

Eliminate The SyncAnother method of disabling the

AFPC during tests or adjustmentsis to ground the grid or base of thesync separator. However, the AFPCcomponents remain in the circuit,so the technique has more possi-bility of mistakes when we aretrying to determine where thedefect is located.

Ringing CoilIn Figure 1, the component

labelled "stabilizing coil" plays animportant, but secondary role inthe oscillator frequency. The vari-able inductance of the coil alongwith the capacitance of the .0033paralleling capacitor form a tunedcircuit that resonates near thehorizontal frequency. It improvesthe noise immunity of the horizon-tal oscillator. Also, it helps mini-mize drift of the oscillator fre-quency. If the coil is misadjusted,both of these advantages are re-duced.

However, the importance of theseringing components to our methodsof troubleshooting can be con-densed as follows: Adjustments of the coil affect theoscillator frequency (a few poorly -designed models used the core ofthe ringing coil as the hold con-trol!); and When the ringing coil and capaci-tor are resonant at the properfrequency, the coil can be shortedout without any change of oscillatorfrequency.

The first item warns us that amisadjusted ringing coil can causea wrong horizontal frequency. (Al-so, it can be misadjusted toproduce the correct frequency froman off -frequency oscillator. In otherwords, two wrongs can make the

frequency right-but, with the prob-lems of drift and susceptibility tonoise remaining unsolved.)

The second item reveals a con-venient method of adjusting theringing coil correctly, without in-struments.

Adjusting the ringing coilHere are the steps for fast and

accurate adjustment of both thehorizontal hold and the ringingcoil: Defeat the AFPC by groundingthe grid of the sync separator tube(this makes any slight change offrequency very noticeable, sincethere is no automatic correction); Disable the ringing coil (by con-necting a short jumper wire acrossthe terminals, or by bypassing thetest -point end with an electrolyticcapacitor); Adjust the horizontal -hold con-trol for zero beat (or, as near aspossible);

Remove the jumper or capacitorfrom the ringing coil; Without changing the horizontal -hold adjustment, adjust the ringingcoil for the same degree of zerobeat as obtained before; and Remove the short from thesync -separator grid.

The horizontal locking should bevery accurate, and not require anyhold -control adjustments for sometime. Of course, this is assumingthat there are no defective parts inthe circuit.

In many cases, the correct adjust-ment of the ringing coil as part ofthe sequence can eliminate minorproblems of oscillator frequencydrift.

Double TriggeringWhen the ringing coil is disabled,

some oscillator circuits will becomeunstable, usually with a patternvariously called parasitic oscillation,


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July, 1978


17

Horizontalcontinued from page 17

double triggering, or "ChristmasTreeing." Generally, the problemcan be traced to open filtercapacitors, or to an unusually lowplate resistor in the first half of themultivibrator. In Figure 1, this isthe 10K plate resistor that suppliespin 1. If the original designspecified a low value (such as 3.9Kor 4.7K), a larger value can besubstituted long enough to set theringing coil. The temporarily -wrongsize produces only a small error ofthe frequency.

Critical ComponentsIn Figure 1, the two components

that are most critical for theoscillator frequency are the 330 pFcoupling capacitor between pins 1

and 7, and the 220K grid returnresistor for pin 7. The 170K, the1.2M, and the horizontal -hold con-trol resistances must NOT have anyappreciable drift from heat. or time.Other components that have someeffect on the frequency include: the2.2K resistor and 470 pF wave -shaping network at pin 6; the 39Land 5.6K plate resistors for pin 6;and the 560 -ohm common -cathoderesistor.

Of course, no leakage can be

tolerated in the 330-pF couplingcapacitor. Equally important is thetemperature coefficient. Don't use agarden variety ceramic. Check theparts list, and obtain the same typefor replacements. In extreme cases,it might be necessary to use anegative -temperature coefficient ora mica type.

Selected ValuesThe capacitor and resistor at the

second grid (pin 7 in Figure 1)

MUST have the proper RC timeconstant so the frequency will bealmost perfect when the sync andringing coil both are defeated. Wemight call this the "natural" fre-quency.

A few models have no horizontal -hold control in that grid circuit,and the ringing coil is used as apoor substitute. For such situations,the circuit of Figure 2 is used as atemporary replacement for the non-adjustable grid resistor.

As shown, both the AFPC controland the ringing coil are disabled.Then, the 500K test control isadjusted for zero beat. Afterwards,the 47K and 500K resistors areremoved (with care to prevent anychange of value) and the total

SHORT

SHORT

HORIZ OSC

-12-"IH- OUTPUT

r - -47K

TEST

GRID

CIRCUIT

500K

LINEAR TAPER

10 M F D

FREQUENCY TEST

8+DECOUPLING

NETWORK

4.7K

+V

Figure 2

resistance of both is measured.Finally, select a fixed resistor of thesame value, and install it perma-nently to replace the original gridresistor.

A Brief Look At AFPCTwo specific input signals are

required for proper operation of theduo -diode AFPC circuit in Figure 1(as well as most other similar ones).A sawtooth waveform from eitherthe oscillator or the flyback is thereference signal. Negative -goingpulses (of lower amplitude than thesawteeth) from the sync separatorare the standard signal.

During correct frequency -and -phase operation of the oscillator,the rectification of those two signalsby the diodes results in a near zeroDC voltage, which is filtered andfed to the pin 2 grid for control ofthe oscillator frequency.

When the oscillator changes to awrong frequency, the diode rectifi-cation of the two signals produces asmall negative or positive DC volt-age, which restores the frequency tothe original value.

Most similar circuits have thesame DC output to the oscillatorwhen the locking is perfect, as theydo if either of the two input signalsis missing. Therefore, a total loss ofhorizontal sync, for example, willnot change the oscillator frequencyvery much.

The two diodes (sometimes pack-aged together) are the componentsthat are most likely to fail in theAFPC circuit. A scope is your bestbet for the waveforms, and aVTVM or digital meter should beused to measure the DC voltages.

Leakage in either the .001 or the.047 capacitors located near thegrid of pin 2 can cause the looselocking, and yet all other parts andwaveforms will be perfect. Keepthis in mind, for it is oftenoverlooked.

Next MonthThe critical components and

adjustments in other basic types ofhorizontal oscillators are included,along with more troubleshootingtips. El


CARTOON CORNER

"And you know sonny,they say it's one of the first TVs made."

"Oh yes ma'am!We have some of the best technicians in town!"

"I'm not telling him it suddenlystarted working when I plugged It in!"

July, 1978 19

The Basics ofIndustrial Electronics,

Part13

Timers, Clocks,and Toggled

Flip Flops

By J. A. "Sam" Wilson, CET

Most versatile of all flip flops isthe J -K type, which was introducedlast month in this series. Oneimportant application for J -K flipflops is in electronic counters. But,before electronic counters, we mustconsider electronic timers.

Electronic TimersUsually, we think of timers as

mechanical or electronic devices(such as a clock radio) that areused to start or stop an operationof some kind. And, these devicesare used extensively in industrialelectronics. The electronic ormechanical timer of a spot welder,for example, controls the length atime that the current flows, toinsure proper bonding of the metals.

Many home appliances havetimers. Each automatic washer hasan electro/mechanical timer that

controls the minutes of each cycle.Where only a single on/off or

off/on cycle (or a continuous seriesof identical cycles) is needed, anelectronic timer can do a better jobby allowing shorter or longer timedperiods and accurate repeatability.For photographic purposes, someelectronic photo timers offer aselection of times from 0.1 secondto several minutes.

However, in digital circuits, atimer usually is a "clock," which isa square -wave or pulse generator.

The 555 IC is very popular forvarious kinds of electronic timers.It can produce a single on/off cycleof any time up to several hours, orcontinuous square waves with risetimes of 100 nanoseconds. Thisrapid rise and decay time makesthe 555 able to function efficientlyas a generator of clock signals forcounting and display circuits.

The 555 TimerA square -wave generator is our

first application for the 555 timerIC. Other IC timing devices and anin-depth study of the 555 can befound in the IC Timer Cookbook,by Walter G. Jung (Howard Samsbook number 21416).

An astable multivibrator circuitusing a 555 IC is shown in Figure1. The word "astable" indicates thecircuit has no stable state. In otherwords, it is a free -running multi -vibrator oscillator. Many tube oscil-

lators of similar basic principlewere used in the vertical andhorizontal sweep circuits severalyears ago.

Inside the 555The dotted lines of Figure 1

enclose the internal circuitry of the555 IC, while the external compo-nents allow the timer to operate asan astable multivibrator oscillator.(However, if pin 2 is disconnectedfrom pin 6, the circuit can'toscillate continuously. Instead, thepin 3 output state will reverse eachtime a negative -going pulse isapplied to pin 2. This is called"monostable" operation.)

The values of the R1/R2/C2 timeconstant determines the free -run-ning frequency of the oscillator.Capacitor Cl is not essential formany applications, although it doesminimize the possibility of noisetriggering the multivibrator.

Two voltage comparators are inthe IC. The output state of avoltage comparator changes accord-ing to which input has the highestvoltage. Some comparators aremerely operational amplifiers (opamps) that don't have any feedbackto reduce the gain. In fact, the opamp and - input identificationssometimes are used also for voltagecomparators, as shown in Figure 1.Where used, the - indicates theinverting input, and the + is for



CONTROL

VOLTAGE

Cl

THRESHOLD

VOLTAGE

TRIGGER

2

rR3 UPPER

COMPARA'06

R4

6-S FLIP FLOP

LOWER

COMPARATOR

C2

R2

RESET

II

DISCIARGE

+5V

R5

L___

+ VOLTS

Q

Q2

A STABLE MULTIVIBRATOR

INVERTING

POWER

AMP

555

TIMER

1

OUTPUT3

Figure 1 The 555timer iC is versatile.When wired this way,it becomes a multi -vibrator (time -con-stant) oscillator, withan output that's com-patible with TTL cir-cuits.

N\A

A INPUT

B INPUT

DC

C

OUTPUT

VOLTAGE COMPARATOR

Figure 2 Op -amp symbols are used also for voltagecomparators. When voltage at the "A"' input is morepositive than the voltage at "B", the output goeslow. Conversely, when the "A" voltage is lesspositive than the voltage at "B", the output goeshigh. This is illustrated by the waveforms, whichare shown with the correct phase between inputand output.

PIN 2

2/3 VOLTAGE

PIN 21/3 VOLTAGE

+5V

PIN 3OUTPUT

DV

T1 -4) -4T2: -*-

WAVEFORMS OF 555

T1=0.693 (R1 + R21C2T2=0.693 (R21C2T3=0.693 (R1 + 2R2)C2

Figure 3 The sawteeth are shaped by C2, and they are connectedto pins 2 and 6. The square -tipped pulses are the waveform atpin 3, the IC output. Remember, the flip flop output state andthe IC output state are opposite. T1 begins when the lowercomparator drives the flip flop output low. During `1, the flipflop output remains low. At the end of Ti, the upper comparatortriggers the flip flop to a high output. This starts T2 During T2,the flip flop output remains high. At the end of T2, the output ofthe flip flop is driwen low again. This is the end of one cycle ofoperation, and also the beginning of a new T1.

Ju y, 1978 21

Industrialcontinued from page 20

the non -inverting input. In suchcases, the output state of thecomparator is low when the inputhas a higher positive voltage thanthe + input has. Also, the output ishigh when the - input has a lowerpositive than the + input has.Because of the very high gain, onlya few millivolts of voltage differencebetween the two inputs can triggeran output change of state.

Figure 2 shows one way tooperate a voltage comparator. TheB (or + non -inverting) input has afixed DC voltage, and the A (in-verting) input has a triangularwaveform. When the triangle volt-age rises above the DC voltage, theoutput goes low. And when thetriangle waveform is below the DCcomparison voltage, the output ishigh. These relationships and thecorresponding output states areshown by the drawing. If the DCvoltage had been centered on thetriangles, the output would havebeen square waves.

Notice that the output has onlythe usual two digital states: high orlow. Reversing the signals at theinputs also reverses the state of theoutput pulses or square waves.

The 555 as an oscillatorReturning to the circuit of Figure

1, one input of each comparator re-ceives a fixed amount of DC voltage

from the R3/R4/R5 internal voltagedivider. The - input (pin 5 of the555 IC) of the upper comparatorhas about 2/3 of the supply voltage,while the top (or +) input of thelower comparator has about 1/3 ofthe supply voltage.

The other two inputs (pins 2 and6) are connected in parallel, andboth receive a varying DC voltagecoming from the power supplythrough R1 and R2. However, C2 iswired from pins 2 and 6 to ground,and it slows down the speed ofvoltage change.

Without either comparator, theDC voltage at the junction of R2and C2 would be zero when powerwas applied. Then, at a speeddetermined by the R2/C2 timeconstant, the DC voltage would riseslowly up to the supply voltage.However, with the comparatorstriggering the flip flop, the DCvoltage at pins 2 and 6 is forced tomove regularly between the 1/3

supply voltage and the 2/3 supplyvoltage points.

When the DC voltage at pins 2and 6 is between the 1/3 and 2/3

supply voltage limits, both com-parators have identical outputs(necessary to keep the flip flop in astable low state). Let's start ana-lyzing the cycle with the C2 voltagerising at 1/2 supply voltage. When itrises a few millivolts above the 2/3

RI

330K

555 OSCILLATOR TESTEXPERIMENT #1

150 StTO

330

Figure 4 To make a digital clock for the experiment, wire the 555 IC with thesevalues

supply voltage at the other input,the upper comparator switches tothe opposite state, triggering the Sinput of the flip flop, and causingthe flip flop output to go high. Partof this high is inverted by the poweramplifier, and it appears as a lowat pin 3 of the IC.

Also, the output high from theflip flop supplies forward bias fortransistor Ql, and it conductsheavily as it begins to dischargeC2 through R2. As the C2 voltagedecreases slightly below the 2/3

reference voltage at pin 5, theupper comparator reverses the Sinput state of the flip flop. Ofcourse, the flip flop does nothing;this step is necessary to prevent adisallowed condition when the Rinput is changed later.

If not stopped by some otheraction, the C2 voltage eventuallywould be discharged to zero. How-ever, when the C2 voltage dropsslightly below the 1/3 referencevoltage (at the junction of R4 andR5), the lower comparator changesoutput state, thus resetting the flipflop to a low output state. In turn,the inverting power amplifier sup-plies a high to the IC output at pin3.

Also, the low output of the flipflop at Q removes the Q1 forwardbias, and stops the bleeding of theC2 charge by the Q1 conduction.This allows the C2 voltage to beginrising again. As the C2 voltage risesslightly above the 1/3 referencevoltage at R4/R5, the lower com-parator reverses the output state,and with it the state of the flip flopR input. This is the end of oneoperating cycle. Of course, the cycleis repeated over and over again, aslong as power is supplied to the IC,thus the 555 timer is functioning asa continuous oscillator.

Figure 3 gives the waveforms ofthe 555 multivibrator, along withthe formula for the C2 charge anddischarge times. Notice that theramp portion of the sawtoothrequires more time than the retraceportion, because the charging of C2is done through both R1 and R2,while C2 is discharged through R2only.

However, the flip flop and thepower amplifier can have nothingbut high and low states. The outputat pin three consists of square -


T

Q

Q

0-1

0

1

0

J -K TOGGLED FLIP FLOPAND WAVEFORMS

Figure 5 These waveforms of a J -K toggled flipflop prove that the toggle is triggered by thefalling side of the input (notice arrows), andthat the toggling acts as a divide -by -two.

Figure 6 (at right) This is the pinout diagram ofthe 7446 IC, which has two separate J -K flipflops.

tipped pulses (because the chargeand discharge times are not equal),which are satisfactory for TTLoperation.

Don't be misled by the output"power amplifier." It is not ahigh -output amplifier, since theentire 555 IC only draws about 200milliamperes at 5 volts. However,the output is sufficient to operateLEDs.

In practical circuits, C2 can bean electrolytic type, when a lowrepetition rate is wanted. Theresistors should be rated at % watt,or larger.

Experiment #1Construct the astable multivibra-

tor of Figure 4, using these values:680K for RI, 330K for R2, 1

microfarad for C2, and .01 for Cl.Calculate the values of time 1,

time 2, and time 3. Write the figuresat the edge of Figure 4. You shouldobtain about 0.7 seconds for time 1,about .23 seconds for time 2, and

5V

CLK1

PRI

CLR1 [-11[

CLK2 [

PR2

CLR2

7446

7446 IC PINOUT

about .93 seconds for time 3.Measure the time of one completecycle (time 3) by watching the LEDin the circuit you have constructed.

Toggled Flip FlopsJ -K flip flops are valuable be-

cause they can be toggled, as shownin Figure 5. The symbol is that of atoggled flip flop. However, it mightbe a J -K flip flop which has beenwired in a specific way. Eithersquare waves or square -toppedpulses should be applied to thetoggle terminal (T).

As stated before, TTL flip flopstrigger at the trailing edge. InFigure 5, the trailing edges havebeen marked with arrows. Eachtime a trailing edge appears at thetoggle terminal, the output changesstate. However, notice that the Qoutput at the first arrow changesfrom 0 to 1, while the change isfrom 1 to 0 at the next arrow.

The output repetition rate at theQ output is exactly half of that at

K1

Q1

COMMON

K2

Q2

Q2

12

the toggle terminal. That's why thisoperation is sometimes called adivide -by -two.

A popular IC is the 7446, whichhas two separate J -K flip flops in a16 -pin DIP package. The pinout isgiven in Figure 6.

When used as a normal J -K flipflop, each section of the 7446 canbe triggered to a high condition bya low at the preset terminal. And, alow at the clear terminal drives theflip flop to a low condition. Ob-viously, the preset and clear nevershould be allowed to have lows atthe same time. These terminals arethe equivalent of the set and resetin a R -S flip flop.

The Figure 6 pinout shows acommon B+ and a common groundfor the two flip flops. Otherwise,the two flip flops can be operatedindependently. In other words, youcan wire and operate one flip flop,but connect nothing to the otherterminals.


July. 1978 23

Industrialcontinued from page 23

Don't ground unused terminalsThe previous paragraph suggests

an important point about practicallogic wiring.

With vacuum tubes and transis-tors, it is good practice never toallow any terminals to float withoutconnections. An unused grid in atube usually was connected tocathode or ground. This preventedthe floating element from pickingup an undesired signal, or fromdeveloping a negative charge fromswarming electrons.

Not so, with logic circuitry. DONOT GROUND ANY OF THEUNUSED TERMINALS. For ex-ample, think of any logic devicethat has a Q and a 0 output. Theseterminals have signals of oppositepolarity. If you grounded the 0terminal because it wasn't beingused, then sooner or later it wouldattempt to go high. A high terminalthat's connected to ground is thesame as shorting the supply voltageto ground through the IC. THE ICWOULD BE RUINED.

Toggling the J -KFigure 7 shows how to wire a J -K

flip flop for toggling. The clockterminal becomes the toggle input;then the preset, clear, J, and Kterminals are wired to the positiveside of the power supply.

Notice that this wiring is not incontradiction to the previous adviceabout not connecting to any unusedterminals, because these terminalsare used.

CMOS J -K flip flops should NOTbe wired for toggling by thismethod. In fact, it won't work forall types of TTL J -K flip flops. Youshould check the pinouts of eachtype, and observe the manufactur-er's recommendation for wiring anyJ -K flip flop for toggling.

Experiment #2Earlier, the 555 IC timer was ex-

plained, and an experiment verifiedthat it can operate as an astablemultivibrator. In this experiment,the 555 multivibrator is used as aclock to toggle the J -K flip flop.

OSCILLATOR

19r

TOGGLE

(DIVIDER)

TESTING A TOGGLEEXPERIMENT #2

Figure 8 Combine the 555 multivibrator oscillator and one ofthe 7446 J -K flip flops (which is wired to toggle) as anexperiment to prove that a J -K can be made to toggle.

TOGGLE

INPUT

+54

CLOCK

PR

CLR

A J -K FLIP FLOP CAN BEWIRED TO TOGGLE

Figure 7 A J -K flip flop can be madeto toggle by wiring it as shown.

Both of these circuits were detailedbefore, so Figure 8 shows only ablock diagram of the intercon-nections and the logic probes.

If you have wired everythingproperly, the second LED at the

TABLE 1

The Decimal Versus Binary Systems

DecimalNumber

BinaryNumber

tens units 23 22 21 20

0 0 0 0 0 0

0 1 0 0 0

0 2 0 9 0

0 3 0 0 1

0 4 0 1 0 0

0 5 0 1 0

0 6 0 1 0

0 7 1 0 0

0 8 1 0 0 0

0 9 1 0 0

0 1 0 0

1 1 0

1 2 1 1 0 0

1 3 1 1 0

4 1 1 0

5 1 1


output of the toggle will flash atexactly half the rate of the first one.If the first LED flashes too fast forgood observation, parallel anothercapacitor or two across C2 until theflashes slow down.

Binary Numbering SystemUntil now, we have ignored the

binary numbering system because itdid not help explain the digitalcircuitry. Now, however, we mustpause and learn the basics ofbinary counting. The next subject isabout counters and display systems,which are designed to operate inthe binary system.

People count by tens because thenorm is ten fingers. But, there areother systems of counting. Forexample, many electronic deviceshave just two states of operation,such as on/off, saturated/not-saturated, glowing/not-glowing,energized/not-energized, and manymore. So, a system of counting bytwos (binary) can be very useful.

Table 1 shows the decimal count

from 0 to 15. The decimal systemhas ten individual symbols-one foreach number 0 through 9. Then,when you reach the count of 9, allof the symbols are used up, and it'snecessary to start a new column atthe left. The new column uses thesame ten symbols over again. Tocount up to decimal 15, then, twocolumns are required.

The binary system has only twosymbols: 0 and 1. The first fourcolumns are numbered 2°, 21, 22,and 23, which correspond with thedecimal numbers 1, 2, 4, and 8.Later, you'll discover an importantreason for identifying the columnsin this way.

Patterns of the countsIn the binary columns, the first

number corresponding to decimal 0also is 0 in binary (or 0000, for allfour columns). The next number is0001 for decimal 1. This has usedup both symbols in the 2° column,so a new column must be started atthe left, making 0010 for 2. Adding

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a 1 to the last column changes it to0011 for 3. Next, a 1 is added tothe 22 column, for a 0100 (or 4). It'sfollowed by 0101 for decimal 5, and0110 for 6, and finally filling thethree columns, 0111 for decimal 7.And so on, until the binary numberis 1111 for decimal 15.

Did you notice the progressivepattern? In binary work, you willfind it very helpful to identify thispattern.

The ones in these columns havedecimal values, but at the begin-ning I suggest that you learn thepattern for counting. In a pinch,you can start with a number youknow and write down the numbersin sequence until you reach the oneyou want.

Next MonthMore information about binary

counting and how to use toggledflip flops as frequency counters willbe presented next month. If possi-ble, keep the circuit of Figure 8 setup for the next experiment. El

The next time you needa tuner repaired or module rebuilt:

RememberFAST SERVICE

RememberPROFESSIONAL QUAUTY

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Circle (9) on Reply CardJuly, 1978


25

service Management seminar, Part 7

The Philosophyof Pricing By pc, G,._ CE.

After you havecalculated howmuch you SHOULDcharge, the nextstep is decidingwhat rates youWILL charge.

Decision TimeDuring the past few months, you

have been making decisions aboutmany things. However, most ofthese were minor, and not really thekind to raise your blood pressurefrom worry.

No doubt, you have done most ofthese beneficial things: set new financial goals for your-self and your business; learned how to read P&L state-ments and balance sheets, thusidentifying and correcting any weakareas of expenses or income; and calculated your productivity, com-paring it to the industry average.

These actions should have in-creased income and efficiency, whilereducing expenses and waste asmuch as possible.

Probably you now have a good,tight operation. But there's onemore item you lack: an increasedincome from profits and return -on -investment which also allows areserve for future business growth.

Previous articles have shown twomethods of calculating the servicerates that you need and deserve.Probably you have arrived at yourown figure by now. If the proposedservice rates show a drastic increaseover your present ones, it's likely

Table 1Figures for 100% Price Increase

Call Rate Total Jobs Total Income.

$20 100

$40 80

$2,000

$3,200

you are afraid to adopt them!YOU'RE CERTAIN NONE OFYOUR CUSTOMERS WILL PAYTHE NEW RATES, and you willlose all of your present volume ofbusiness.

If that is your reaction, don't besurprised. Such a dilemma is facedby almost all managers of smallbusinesses.

The thinking goes something likethis: If the competitor's prices werenot so low, I might be able toincrease my rates slightly. If the products I service cost thecustomers more, the owners mightbe more willing to pay higher repairprices.

Table 2100% Price IncreaseAnd 40% Job Loss

Call Rate Total Jobs Total Income

$20 100 $2,000

$40 60 $2,400


If I could refuse all of thoseunprofitable repairs, perhaps thepresent rates would be satisfactory. If I could sell more parts andaccessories, those profits mightcompensate for insufficient incomefrom labor.

These four kinds of wishfulthinking were thrashed out before.In this painful decision, none ofthem are relevant. And, decisiontime is NOW.

If you can't succeed in receivingadequate compensation for yourefficient operation, then your busi-ness is bound to fail, either quicklyor slowly as you dissipate yourinvestment.

The AnswerAt this point, the only answer

you need (to the question of raisingyour rates) is what effect theproposed increase will have on yourbusiness volume. Nothing else isimportant.

The experience of others whohave faced the same problem showsthat the fear of failure from higherrates is about 10% real and 90%imaginary.

You can solve the dilemma by a"Philosophy of Pricing" that'sbased on these four factors:

Are myrates fair?

COURAGE, COMPETENCE, CREDIBILITY, and CURRENCY.

CourageGreat courage is needed to

charge realistic prices, especially ifyou have a hungry close competitorwho's still charging 1970 prices.

CompetenceOf course, you must have suffi-

cient technical ability, parts stock,test equipment, shop facilities, anda good public image to justify theproposed rates. This does notrequire perfection, which is impos-sible to achieve. But, your ability toperform must not be less than yourcustomers expect.

CredibilityCredibility goes beyond mere

honesty (which is expected), for itmust convince the customers thatyour prices are fair. Customersneed proof of the value you havecharged for. A TV shows nooutward sign of the dozen hours ofpainful labor needed to solve a"dog" problem. You must tellthem. If you used $1,200 worth oftest equipment to locate the defect,it adds credibility to mention thefact. Sometimes solving a minorextra problem (curing a noisyvolume control with tuner cleaner,for example) will convince a cus-tomer that you give added value.

Customers are just as likely tocomplain about a low, below -costrepair as a profitable one. However,they all want value, and you mustgive evidence of value received.

CurrencyCurrency, the money you need to

operate, will come as the result ofthe other three "Cs"-Courage,

Competence, and Credibility. Theseare far more effective than yourself-righteous indignation towardany customer with arrogance enoughto question your rates.

A Good ReasonTo Charge More

One fellow CET formerly was ashop owner, and now is an investi-gator for a state licensing board.

Will my customersgo elsewhere?

Recently, I asked him about themain cause of customer complaintsagainst servicers. He answeredquickly, "The servicers who get intotrouble most often don't chargeenough for their work." This is thereverse of our usual beliefs.

Problems of low pricesMany problems for both you and

your customers occur because youdon't charge enough. For example,you try to crowd in extra repairs tomake a small profit despite below -cost rates. The pressure causes youto make mistakes, requiring num-erous recalls. These recalls are donegrudgingly because of the lack oftime and not having any profit topay for the extra repair. In turn,your sour face, and his suspicionabout why a second repair wasnecessary, detracts from your credi-bility.

Other problems arise because youcontinued on page 28

27

Service Managementcontinued from page 27

Table 3Price Increase, Job Loss, Parts Income

Call Rate Total Jobs Parts Sales Total Income

$20 100 $1,000$40 60 $ 600

$3,000

$3,000

CALCULATION: Labor income increaseDecrease of parts profit (50%)Subtotal

$400-$200$200

Decreased overhead $100Decreased labor costs + $300Subtotal $400

TOTAL GAIN

$200+ $400

$600

can't afford enough employees,adequate test equipment, and acompetent office staff.

Even worse, your desperate desireto break even might tempt you tocharge for work not done or partsnot installed. The justification isthat the customer is paying nomore than if you charged properlabor without the false items.

Will my shopget a "high price"

reputation?

Regardless of rationalization, it'sstill petty thievery.

Forcing your customers to settlefor someone of less competence isone possible indirect disadvantageto the community, when yourbelow -cost prices drive you out ofbusiness. Your distributors sufferwhen you can't afford to buyproper test equipment and supplies,and the government loses the taxesyou would pay if you made a profit.

Your family is cheated by the longhours of overtime you work just tomake a bare living. Even yourneighborhood is penalized becauseyour run-down shop eventually be-comes an eyesore.

Advantages of higher pricesAfter you increase your labor

rates, your competitors invariablyraise theirs. So, your "higher"prices rapidly become "average."Also, those higher rates tend toconvince the set owners that yourservice is better than the low-pricedshops. Fewer old sets with difficultmultiple troubles will be brought toyou, thus eliminating most of thejunk sets, which often requireextensive and unprofitable repairs.

The higher income will allow youto hire more -experienced techni-cians, and purchase needed testequipment and supplies. Thetemptation to charge for parts orlabor that are not delivered will belessened.

Probably you know of two shopsin your area. One charges twice theper -hour rate of the other. Yet thehigher -priced servicer usually hasmost of the business. This usually isthe case.

Still not convinced? Then readabout what is likely to happenwhen you increase your rates.

After The Price Increase?Let's imagine that your previous

service call price was $20, and youincrease it 25% (up to $25).Further, we'll assume a 10% loss ofcalls because of resistance to theprice increase.

Previously, your income for 100calls totalled $2,000. With the newrate, the remaining 90 calls willbring in $2,250, which is anincrease of $250 for doing 10%fewer calls.

Of course, the $250 is not pureprofit, for you have eliminated theparts profit from those calls notmade. If you average $10 per call ofprofit from parts, the $250 isreduced to only $150. On the otherhand, you have saved truck andoverhead expenses, thus bringingthe total up to perhaps $200. Thisrepresents a 10% increase of incomewith a 10% reduction of time andwork.

Calls Remain The SameActually, those previous figures

are too pessimistic, because thereare no known cases of such amoderate price increase reducingthe business volume.

Experiences around the entirecountry show that only extremeprice increases produce any loss ofbusiness.

Double Rate?For example, let's assume the

service -call rate of $20 is increasedto $40 (that's double-or a 100%increase). I estimate that the shopmight lose no more than 20% of theservice volume. And this includesany long-term reduction caused bythe competition keeping the oldrates.

If you disagree with this 20%estimate, use the form of Table 1,and calculate by your own figures.

If overhead costs and wagesremain the same before and afterthe raise, the Table 1 $1,200increase of income is largely pureprofit.

Worst CaseWe'll assume you have properly

calculated your costs and foundthat $40 per call is absolutelynecessary to provide a modest


profit. By disregarding the truth,you expect a 40% loss of repair jobsbecause of the higher rates. Now,what financial change will bebrought by a 40% loss of customersand a 100% price increase? Table 2tells the glad story. Without in-cluding any other factors, theincome is $400 (20%) higher!

Next, we'll calculate the completegains and losses (see Table 3). Thefinal gain of income is $600, whichis higher than the bare estimate.

Calculate The EffectsOf Pricing Change

The purpose of this article isNOT to convince you, to RAISEyour labor rates, but to give you amethod of forecasting the effects ofany price change you might make.Many service -shop owners alreadyknow they need a certain priceadjustment. But, they delay becauseof fears that the customers willcomplain loudly, and probably taketheir business elsewhere.

After you make any change ofrates, I recommend you MEASUREany effects of the price change.Disregarding any unusual financialfactors (extreme weather, a costlystrike in the area, etc.), check yourdaily, weekly, and monthly volumeagainst the same time period lastyear during the old rate.

Also, urge your employees towrite down every case where acustomer complains about the price.Chances are, you will find very fewlegitimate price complaints. Prob-ably, no more than you received atthe old rates.

If you still worry about thebacklash from rate changes, makegradual price adjustments andmonitor the results each time.

I can't survivemuch longer

on mycurrent rates

CommentsComparison shopping is a per-

manent part of our modern life.Price comparisons between identicalproducts in different stores can bedone easily with high accuracy. AllBuicks (or Plymouths or Pacers)come from the same factory; theprices vary only at the whim of thedealer.

Other comparisons are moredifficult and less valid. In my area,all barbers charge the same for ahaircut (how has the FTC over-looked that kind of price fixing?),so we choose a barber for his skillor personality. On the other hand,when a broken pipe begins to floodyour home with water, do you call adozen plumbing shops and choosethe one with the lowest price? I amthe patient of a certain doctor, forhe is the only one who was able tohelp me. His office calls haveincreased 50% in the last two years,but I will not go to another.

My point is that some pricecomparisons are valid and helpful,while others are an exercise infutility. Very few electronic -repairprices can be compared directly.Most shops have some kind of aflat -rate price for service calls, andthese prices allow some degree ofcomparison. Even with calls, thereare no standards about the specificservices which are done within thebasic flat -rate price versus othersthat require an extra charge. Be-yond service calls, the price com-parisons become even less accurate.One reason is that, before atechnician examines the machine,the customer doesn't know whatparts and services are needed.

A few customers might callseveral shops to compare theirprices before selecting one. How-ever, most set owners are awarethat such a "bargain" often be-comes a disappointment. Conse-quently, the choice of a service shopusually is done according to thevarious reputations for honesty andcompetency. Credibility is moreimportant than price.

An old saying states, "Qualitywill be remembered long after theprice has been forgotten." Thatprinciple certainly applies to thepricing of electronic repairs. 0

New Slim-Bodscope probes

fromB&K-PRECISION...cost effectiv ;

andreally rugged!B&K-PRECISION s new line of 10:11direct scope probes is designed to becompatible with most scopesavailable, up to 50MHz.All are rated at 500Vp-pB&K-PRECISION slim -body probes range inprice from $25-$35.

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Spring -loaded

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Window clearlyindicates direct

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Slim -bodydesign with steel

inner structure

Compensationcapacitor adjustment

Tough, flexiblecable strain relief

Model Connector Bandw. Matches

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DYNASCANCORPORATION

6460 West Cortland AvenueChicago, Illinois 60635 312/889-9087

L...tn Canada: Atlas Electronics, Ontario./


29

ServicingSylvania Color TV, oneTuning of the take -offand bandpass stages isnot adjustable in thechroma circuit of theSylvania E44 chassis.ICs are used for mostfunctions. A chromasetup switch and severaltestpoints simplify thetroubleshooting. Fol-lowing the circuit ex-planations, severalsuggestions are givenfor troubleshooting thevideo and chromastages.

Figure 1 Components ofboth the video and chromacircuits are located on thechroma module (near thecenter of the chassis), andon a circuit board attachedto the picture -tube socket.

By Gill Grieshaber, CET

Chroma FeaturesMost of the Sylvania E44 video

and chroma circuits are located onthe chroma module (Figure 1). Thevideo signal is amplitude adjustedby three drive controls and thenapplied separately to the emitters ofthe three power transistors thatdrive the three picture -tube cath-odes. The three -Y demodulatedchroma signals drive the properbases of those same color transis-tors (pre -CRT matrixing). Theseplastic -type, medium -power, color -output transistors and their associ-ated components are mounted on acircuit board which is attached tothe picture -tube socket.

All color receivers MUST havecertain basic functions, such as: peaking and bandpass tunedcircuits; chroma IF amplification, de-

modulation, and -Y amplification; adjustments for tint, color killer,color locking, and color saturation.

Of course, the chroma circuit ofthe E44 chassis has all of thosefunctions, using one transistor plustwo -and -a -fraction ICs. However,the three tuned circuits and severalphase -shifting filters are not ad-justable. Such functions as colorsaturation, color tint, color killer,color locking (A PC), automaticchroma-level control (ACC), andcolor threshold are controlled byvarying DC voltages (from poten-tiometers) that are applied to pinsof the ICs. Look for these features,as the circuit operation is explained.

Because ICs are "black boxes"whose internal circuits are notshown, the functions of manycomponents connected to the ICsare difficult to understand. There -


fore, most components will bedesignated according to circuit orfunction.

Waveforms are of highest im-portance in video and chromacircuits, so all those needed forservicing will be shown. In thischroma system, many of the DCvoltages change according to thechroma level and the adjustment ofthe various controls, as well asbeing different for monochromesignals. Typical DC voltages forvarious conditions are listed.

Locations of the major chromacomponents are pointed out byarrows in Figure 2, while theschematic is in Figure 3.

The TC or TD numbers shownon the schematic refer to themodule pins, which are plainlymarked on the module surface.

First Chroma AmplifierNegative -going video enters the

chroma circuit at module pin TC43.R670, C666, C664, R668, and L670together form a low -Q resonantcircuit that tunes to about 4 MHz.(C664 and L670 are the principaltuned components.)

Notice that only 3.58 -MHzchroma and burst remain after theinput video color -bar signal (W1 inFigure 4) reaches IC602 pin 2 (W2),after passing through the takeofffilter and coupling capacitor C660.(A color -bar generator with thechroma on black pedestals was thesource of the signal at the TVantenna terminals.)

Inside IC602, the chroma IFsignal is amplified slightly, and itcomes out at pin 3. Incidentally,IC602 is shown in three sections, to

SW602

T D11

IC602 -1

TD15

Q602

1C900

17 si

2

4

CRYSTALXT600

10604

TC31

TC34

TC37

TC43

DL900

TC48

TC49

TC50

Figure 2 Arrows point out the locations of important chroma ICs, test points,and one transistor.

make the signal -flow paths easier tofollow.

One reason for the moderatevoltage gain (about 21/2) is theAutomatic Chroma-gain Control(ACC) DC voltages that are appliedto IC602 pins 1 and 16. Variationsof the DC voltage BETWEEN thesepins control the gain of the first

chroma amplifier. These DC volt-ages vary slightly below and above+8 volts, with the pin 1 voltagedecreasing with a stronger chromasignal, and pin 16 voltage in-creasing with stronger input chromalevel. This action is detailed inTable 1.


July, 1978 31

TC31

CHROMATAKEOFF

R668 >3300.>

L670

POSITIVE

HORIZ PULSES

FROM IC900PIN 15

8V PP

+ 1.49V

R610 C600

10K 01

BORST

KIYIRG

CHROMA

?V PP

-1 53VW2

1ST

CHROMA

AMP

PART OF IC602

1

C668

+ 8.07V~ 5F

+127

R674 100

R680:47K

-005

0672

+ 8 14V

4.7V PP

- 2.65V

C601 5ElpF

10KR612 < 150K

137

BURST

GATING

8

1:.8V

15

IN3

16

+ 8 14V

5V PP

+ 19.42V

+ 12V

R672 100

R676

22K

""-- ACC-v.

ACC

8678

+ 8.20V

16

IC604

47K

C670

05

3 8MHz APC

/OS \s

C690-68pF

6

+ 12.2V + 2.86V

C692-12pF

XT600

to3.58MHz

C692 22pF CRYSTAL

1

R704-Vs/st270K

-8.75+ 8.75

C68° R686

1000

R688'VVN,4700

R684

R666

APCR694

R692

+ 6.84V

12

13

APC

10

+ 19.42V

200

SW602

R702

NORMC688

ALIGN

15V PP

L680

C682 33pF

R690 R700

220pF1500=.-

TINT

R708

478

+ 127R710

C676

2682 47K -

47K

C6P8 5 C674 401

+12V

17V PP

TINT

+ 12V

7.37C696

47pF

47K R706

C700

.011-1

TC34

R714 TINT

10K

14

C656

I(001

220pF

15V PP

+ 12V

ACCR698

r{

R696 470K

01

+6.84V

2

+ 12V

W12 6V PP I W13 k

1 2V PP

00011700

1500

+ 12V

+ 12V

ACC

C69727pF

C698.":"F 270pF

CHROMAMODULE

Sylvaniacontinued from page 31

The ACC DC voltage is suppliedby IC604 pins 15 and 16, and thechroma level is sensed by theWaveform 10 signal at pin 14. :naddition, the adjustable DC voltageat pin 14 is used during the chromasetup alignment. These three pins(14, 15 and 16) of IC604 are usedfor ACC. Testpoints "P" and "M"

are connected to the ACC voltagesat pins 15 and 16.

Chroma-Bandpass AmplifierFrom IC602 pin 3, the chroma-IF

signal goes through coupling capaci-tor C656 to pin 4, where the signalis amplified slightly, coming out atpin 14.

L650 and C642 tune to about3.58 MHz, and R655 flattens theresponse, as required for a band-pass stage. This bandpass circuitand the takeoff tuned circuit at pin2 are the only two resonant circuitsin the chroma IF. Neither isadjustable. The signal from pin 14is ready for the demodulators.


IW4 35V

4

+ 1 02d

2A11) CHROMA AMP

COLOR KILLERPART OF IC602

6

+ 7 05V

15+ 21 5

V

+9.92VCOLOR

+11 B&W

14

W5

CHROIAABANDPASS

+20 9:

2

L450 ,=0=d R655

C631 .8656

H. .,,,,,_.2.2AF 2 7M

C633 0646

C6331

0- 1

1-101 F101'--- " R650 100

u,"OLOR

6660w KILLER 8662

R654 470

11658

27K 100h 1000

C640

48V PP

3300

C642

39pF

05

+ 24V

+ 24V

W6

C64413

001 + 5.30V

45V PP

W16 =61iIV PP

C618 ":-.-22(pF

+ 12v0 0

0L658

DEMODS

PART OF IC602

W17

R616 100

Q602

CHROMA 3UFFE

C618 +5.54V

.82pF

I W5R618 226

.43V PP+1.2V

7

MO COLOR DETPART OF IC900

9

R645 27.K

R630 R644

50K

COLOR

THRESH

Figure 3 This is the ctiroma schematic, except for the matrixing color amp lifiers. The DC and peak -to -peakvoltages shown here were measured during color -bar operation, and the waveforms are in Figure 4.

6800

TD15

8

IV PP

+12V

C652=220pF

R606

270

R607

+1344V R955

680

R953 3300

C915

+ 13.64V

liR962

10 680

6961 3300

C916 220pF

1348V R947

C654 6945

2001(71-

C636

68pF

15K

C634

T049

2V PP

TC48

WS

6.46 PP

TC50

680

3300

C914 T 220PF76I6.3V PP

"PERMATINT

'ON +.63VOFF OV

SC600

01+24V

TD11

SW600

4700

ON

GY

BY

RY

1 PERMATINT

OFF

TO PICTURE

CONTROL

MIN COLOR +1.4VMAX COLOR +9.4V

The pin 14 signal has anotherjob. It's buffered by emitter -followerQ602 transistor, and is applied toIC900 pin 7 (the video IC). The DCvoltage output from 10900 pin 8 isfiltered and applied to pin 6 of10602. This DC voltage controls thegain of the second chroma amplifieraccording to the average chroma

level. The ACC, to be describedlater, controls the gain of the firstchroma amplifier according to theburst level, which is independent ofthe chroma amplitude. Both circuitstogether provide steady, consistentcolor saturation.

Another function-the color killer-operates in the same part of

IC602, although most of the com-ponents are hidden inside the IC.The DC voltage at pin 15 (from thekiller control) determines the exactminimum chroma level where thekiller eliminates the gain of thesecond chroma stage.

Before analyzing the demodula-continued on page 34

July, 1978 33


tors-which also are inside IC602-we will describe the 3.58 -MHzoscillator, color locking (APC), ACC,and tint circuits.

10604 FunctionsPins 7, 8, and 6 of IC604 are

used for the 3.58 -MHz oscillator.Horizontal pulses at pin 4 allowgating of the burst for the APCcolor -oscillator locking. In addition,

pins 11 and 12 connect external RCfilters to the internal APC circuit.These pins (and pin 13) are theones to test, if a defect happens inthe color oscillator.

ACC operation (according to theburst amplitude) uses pins 15 and16 to filter the ACC DC voltages(previously described) that are ap-plied to the first-chroma amplifierin IC602. Chroma that contains theburst comes from IC602 pin 3 andis applied to IC604 pin 14.

A sample of the chroma signal at

pin 14 is phase -delayed by L680,C682, and R690 before it is appliedto pin 13, for use in the APC.

Changes of DC voltage at pin 1vary the tint by changing the phaseof the 3.58 -MHz carrier that is sentfrom pin 2 to the demodulators. Aphase shifting network is connectedbetween pins 2 and 3, and the levelat pin 3 changes drastically withtint variations, especially near the"green faces" end of the front -paneltint control. In this particularchassis, the DC voltage at pin 1

W14

W15

W3

411W4

401041101411

W10

W11

W16

W17

4111111111.1111111

Figure 4 These waveforms are for the Figure 3 circuit. Thecolor bars have black bars between them; so W1 might bedifferent when you use your color/bar generator. Wave-forms W2 through W6, and W10 through W11, arechroma-IF signals. Notice the first bar (burst) is notblanked out of any waveforms. Waveforms W7 through W9are the demodulator outputs. W12 and W13 are 3.58 -MHz

W5

.14110041111%W6101100~.

W12

111111M,W13

Left-W16 EXPANDEDRight-W17 EXPANDED

CW signals of the tint circuit, shown at the horizontal rate;notice the horiz blanking. W12 varies in amplitude with thetint adjustment. W16 and W17 are the 3.58 -MHz CWsignals for the demodulators. Scoped at horiz rate, they areidentical. When expanded by the triggered scope, thephase difference is shown.


varied between +7.21 for greenfaces to +7.55 for purple faces.

Test probe warningSeveral pins of IC604 are sensi-

tive to the extra capacitance of anX1 scope probe, or a digital meterwithout an isolation resistor in theprobe. When such a high -capaci-tance probe is connected to pins 6,7, or 8, the 3.58 -MHz oscillatorstops, thus eliminating all color.

In the same way, excessive ca-pacitance at pins 1, 2, and 3 of thetint circuit shifts the tint by variousamounts.

DemodulatorsThe chroma signal from the pin

14 output of the second-chromaamplifier goes through C644 to pin13 and the three demodulators ofIC602. A direct 3.58 -MHz carrier(without phase shift) from pin 2 ofIC604 is brought to pin 8 of IC602,through C648. Part of this signal isphase shifted (delayed) by L658,C654, and R606, before it is sentthrough C652 to pin 7. The phasedifference between pins 8 and 7 isabout 90 degrees.

This 90 -degree phase differencecan be increased by the "Permatint"switch and circuit. When switchSW600 is slid to the on position.+24 volts is applied to R607. Thevoltage at the other end of R607biases diode SC600 into conduction,thus grounding the cold end ofC636. C636, therefore, is connectedin parallel with C654, and thephase of the carrier at pin 7 isdelayed even more than the origi-nal 90 degrees.

After demodulation between thechroma-IF signal and the various3.58 -MHz CW signals, the un-filtered R -Y, B -Y, and G -Y wave-forms emerge at pins 10, 11, and 9respectively. Ripple in these signalscauses the waveforms to appearfuzzy. Therefore, we usually examinethem following the RC filters(R94 7/C914, R962/C916, andR955/C915), as shown by W7, W8,and W9.

These three -Y signals are sent tothe bases of the three color ampli-fiers (Q912, Q916, and Q914). Themonochroma video is applied to allemitters of the same color ampli-fiers, to complete the matrixing.

Table 1ACC DC Voltages

Signal = none

Pin 1

Pin 16

Difference

weak medium strong

+ 8.23 + 8.21 + 8.09 + 8.06

+ 7.97 + 8.05 +8.16 +8.15-0.26 -0.16 +0.07 + 0.09

(Both were + 8.75V in the ALIGN position)

Table 1 These DC ACC voltages were measured at IC602 for various signalstrengths.

Matrixing AndColor Amplification

Video (which has vertical andhorizontal blanking) leaves thechroma module at terminal TD22,goes through 5900 service/normalswitch, and returns through a coilto terminal TC54 of the samechroma module. That's because thevideo drive controls are on thechroma board.

When 5900 is in the serviceposition, the video is disconnected(which also eliminates any bright-ness adjustments) and positive -going horizontal pulses of 0.7 VPPare added to the drive controls (andeventually, the emitters of thecolor -output transistors). Thesepulses cause positive pulses ofabout 20 VPP at all cathodes of thepicture tube for retrace blanking.

Figure 5 shows the wiring of thedrive controls (on the chromamodule) and the green, blue, andred output transistors, which aremounted on a module that'sfastened to the picture -tube socket.

Color outputsOne power transistor is provided

for each of the three colors. Thevideo is applied to each emitter,and a G -Y, B -Y, or R -Y demodu-lated-chroma signal is brought toeach base. The base/emitter con-duction plus the unbypassed emit-ter resistors (that bring in the video)produces some unexpected wave-forms. For example, chroma andsome video is found at the bases;also video and some chroma isfound at the emitters. Blankingpulses of some amplitude can beseen at base, emitter, and collector.

Therefore, you should study thewaveforms of Figure 6.

Matrixing of the chroma -Ysignal and the video signal is doneinside each color output transistor.

Since both signals are applied toeach picture -tube cathode, thepicture -tube grids have no ACsignals. Instead, they have a fixedbias of about +30 volts applied toall three in parallel. Of course,remember that the grid voltagedoes affect the overall brightness.

TroubleshootingFor troubleshooting video circuits

such as the ones in the SylvaniaE44, the recommended test instru-ments are a good scope (preferablyof triggered -sweep and dual -tracetype) and a digital multimeter.

With the scope, begin with thevideo input at terminal TC43 of thechroma module, and then traceeach stage in consecutive orderuntil you locate the one where thevideo problem first can be seen.

After the approximate location ofthe defect has been pinpointed,DC -voltage tests and transistorchecks should be made. The tran-sistor sockets are a welcome helpwhen transistor testing is required.

Usually, ICs can't be tested ade-quately. So, just check for thecorrect incoming waveforms and alloutgoing waveforms. Next, measureall IC DC voltages. If the inputsignals are there, and the DCvoltages are okay, but there is nooutput signal, then it's a good betthe IC is bad.

Probably the most difficult thingabout video testing is the several


July, 1978 35

S900

SERV -4-- NORMAL , r

R943

476

HORIZ

PULSES

11I

TD221

VIDEO FROM

EMITTER OF Q904

I

I W1 0L954

II

TD54

e

I

I I L

GY

IC602

PIN 9

R974

150

B&W+ 12.64V5.5VPP

BARS+ 1 3'7°V3 .2 VPP

R955

R953

3300

GREEN DRIVE

BY

IC602

PIN 11

R994

150

B&W+4.1 5V1.4VPP

TC49 R976

680

R958

150

R962

R961

3300

BLUE DRIVE

BY

10602

PIN 10R945

3300

R965

150

RED DRIVE

CHROMA

MODULE

C915I 220pF

R956

4700

680

R966

150

R947

C916

220pF

1R964

4700

Wilif 100

I BAFiS+14 35V1 3VPPe

TC53

B&w+14.1 2V.2VPP

TC4B R983

W4 100

1 BARS+14'40V3.5VPP

TC52

1

I B&W + 14 11V1 3VPP

TC50 R968

100

I BARS +14.39V1 3 8VPP

680

R952

150

C914

220pF

R950

J

4700

Figure 5 Matrixing is done by applying a -Y signal to thebase, and the monochrome video signal to the emitter, ofeach color power -transistor. Each of the three transistorshas a drive control that's adjusted during the gray -scaletracking for B&W pictures. Two sets of DC and PP voltagesare listed, because the color -bar readings were drastically

TC51

R975

Q914

GREEN OUTPUT

pzw+13.69V1 7VPP

-4-W2

R973BARS+1 3.8 8V

1 .7VPP56

R934

R982

56

R969

R967

56

B&W+1 3'64V1.7VPP

BARS." 3'9 4V3 .3VPP

R979 L970

2700+141.5V

B&W112VPP

-41-W3

BARS+1 73.3V7OVPP

R9778200

+ 202V

R986

27000916

BLUEOUTPUTB'" 1 00VPP-4- W6

BARS +1 7 2'5V9 2VPP

L980

R9858200

+202V

Q912

RED OUTPUT

B&W+ 1 3.65V1 .9VPP

W8

BARS+13.95V3.2VPP

R971 L960

2700

1 41.2V"`"' 116VPP

-4-0,/BARS+ 171'1V

100VPP

R9708200

+ 202V

R991

GREEN CRT

CATHODE

BLUE CRT

CATHODE

RED CRT

CATHODE

+ 31 4V

R989 /ALL CRT

GRIDS

different front the B&W measurements. Also, thesevoltages do not precisely agree with Figure 3 (severalcontrols were readjusted between the two tests). The colorbars and the 4 -step -gray -scale video pattern came from anAmerican Technology ATC-10 generator.


stages that are direct coupled. Ofcourse, there are no real closedloops, so usually the DC voltageswill be out of tolerance onlyfollowing the defective stage. We'lltry to expound about servicingdirect coupled stages in a laterarticle.

Chroma troubleshooting is simi-

lar, and a good scope and accurateDC meter are the best test instru-ments. Before the video and chromamatrixing, there are few direct -coupled stages in the chroma. Thissimplifies most servicing.

Except for the APC control,which adjusts the color -oscillatorfrequency for proper locking, andthe color -killer control there shouldbe no adjustments needed in thechroma channel. The align position

of switch SW602 removes all colorlocking and the ACC operation.Then, it is necessary only to adjustthe APC control so the colors driftsideways slowly and uprightly. Af-terward, the switch is slid to thenormal position. That's all.

Next MonthDetails of the sound IF and

audio circuits will be discussed nextmonth in Part 7.


W1 GREEN0914 BASE

y

Ilt t

111;

W4 BLUE0916 BASE

ir.... (`t.._ elri.,........ .lie.i.A l.i.t4tillititlik

irAWMt it 0110) II A 1St it t it P 0 itPr4VIMv 1,10

:1,1,11Jclliii

IVv

1141

W7 RED0912 BASE

UP

IttIMIT Itir

W2 GREENQ914 EMITTER

W5 BLUE0916 EMITTER

W8 RED0912 EMITTER

111111MINilik.

sommommor-ll

W10 W11

TC22 GREEN, BLUE, AND REDCOLLECTORS

L.-

'v4Aqrd-vtrwfLtti4At

W3 GREEN0914 COLLECTOR

1111.1LIMM.1--1M1111111.1 11111MMINO

17317/4."1111t:'?

W6 BLUE0916 CO_LECTOR

W9 RED0912 COL_EC-OR

Figure 6 -hese are the waveforms ofFigure 5 W1 shows the video wave-form (top) and the color-ba- waveform(bottom) for the base of 0914. W2shows the same sequence of emitterwaveforms, and W2 display.fs the samefor the collector of Q914. W4 tnroughW9 have corresponding waveforms forthe other two transistors. W10 dis-plays the 3&W and color waveforms atmodule TC22 (also TC54:r, and W11shows the three collector signals atthe vertical rate.

July, 1978 37

III Sam Wilson's' Technical Notebook

0

Magnetic Memories 0

and DiodeProtection By J A Sam ,,,,on CET

Your comments or questionsare welcome. Please give uspermission to quote fromyour letters. Write to Sam at:

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

A Simple Magnetic MemoryThe reviews of basic magnetism

in this column are intended toprepare you for some actual mag-netic devices. A simple type ofdigital magnetic memory will bediscussed at the end of this section.

Summary of magneticsMagnetic circuits and electric

circuits do have some similaritiesthat, unfortunately, are used toooften in teaching magnetics. How-ever, they are widely different inmany important respects, so adirect analogy can lead to seriousconfusion.

It is common practice to equatemagnetomotive force with voltage,flux with current, and reluctance

CURRENT

THERMISTOR

RESISTANCE

WILL OHM'S LAW WORK?

Figure 1 Of the three basic Ohm's Law formulas, onlyR equals E divided by I is accurate with non-linearresistances. Magnetic circuits also are non-linear, soan Ohm's Law for magnetics is impractical.

with resistance. This results in aneat-but misleading-formulacalled "Ohm's Law For MagneticCircuits." It states: Flux equalsmagnetomotive force divided byreluctance. Or, in symbols:

0 MMFR

The formula would be useful andtotally true, except for one fatalflaw: MAGNETIC CIRCUITS AL-MOST NEVER ARE LINEAR.

For an example, let's think aboutsome of the exceptions in electriccircuits where the DC Ohm's Lawis not accurate, either. In thecircuit of Figure 1, only one of the


(A)

FLUX

le)

FLUX

DENSITY

MAGNETIC LINES AND AREA

Figure 2 Becausemagnetic flux can ex-tend beyond the mag-netic material, a read-ing of total flux is oflittle value, in mostcases. The preferredreading lists the num-ber of magnetic linesper square inch (ormagnetic density).

O

O

O


CURRENT

IA)

HIGH MAGNETIC

INTENSITYLOW MAGNETIC INTENSITY

CURRENT

Figure 3 Magnetic in-tensity varies accord-ing to the concentra-

IR) tion.

ZERO

ZERO

APPLIED MHAGNETIZING

FORCE

I` -INPUT CURRENT

(A) VIRGIN B -H MAGNETIZING CURVE

ZERO

ZERO

H -APPLIED MAGNETIZING

FORCE

y HI/

.

1 -..-INPUT CURRENT -0.i

ZERO

H

APPLIED MAGNETIZING

FORCE

/x /

ZERO

CO Gel

INPUT CURRENT -n

(B) SOME FESIDUAL MAGNETISM(X) REMAINS AFTER FORCE IS ZERO

Figure 4 These are foursteps of developing aB -H magnetica sinewave of current.The B -H curve is shownabove the input currentwaveform. (A) the initial

ZERO

CD

magnetization follows adifferent curve than thesubsequent ones do (seethe same part of D). (B)When the current returnsto zero, the flux density

H

APPLIED MAGNETIZING]

FORCE

ZERO

CO

co,

CC

does NOT return to zero.(C) Negative current isrequired to reduce the

CD -Ce,

flux density to zero. (D)This is the complete B -Hcurve (excluding the vir-

-4-

CC gin curve).

(C) REVERSED FORCE (Y) IS REQUIRED 10

REMOVE THE RESIDUAL MAGNETISM

INPUT CURRENT

(D) A COMPLETE B -H CURVE

DEVELOPING A B -H CURVE

July. 1978 39

Technical Notebookcontinued from page 38

three variations of Ohm's Law canbe used. The current varies with theresistance, but the resistance of athermistor depends on the tempera-ture, and the thermistor tempera-ture changes with the current. (Ofcourse, you can measure the voltageand current, and then calculate theresistance. But the other twoformulas have serious errors.) Simi-lar problems of non -linearity occurwith thermistors and diodes.

Magnetic circuits have non -linearity problems comparable tothe one with thermistors. Flux in amagnetic circuit depends on themagnetomotive force versus thereluctance of the material. However,the reluctance varies with theamount of flux. And, as the fluxincreases, so does the reluctance.Such a condition can't be analyzedcorrectly with a simple equation.

Also, two more problems compli-

cate the measurements. Electriccurrent is confined to a conductor,allowing an easy test. But, fluxseldom is contained entirely withina magnetic material. Therefore, anaccurate measurement is the fluxdensity (magnetic lines per squareinch), rather than the total amountof the flux (see Figure 2).

Another problem affecting mag-netic intensity is whether themagnetizing force is spread over ashort distance (Figure 3A), or overa greater distance (Figure 3B).

Developing a B -H CurveA valuable graph can be made by

placing magnetic intensity along thehorizontal axis and the resultingflux density along the vertical axis.In the graphs of Figure 4, weassume that the magnetizing forceis sinusoidal (from the sinewave ofAC current).

H

-B

B -H CURVE FORMATERIAL WITH HIGHRESIDUAL MAGNETISM

B -H

CURVE

MAGNETIZING

FORCE

Figure 5 Some magnetic materials have greater hysterebisthan the one in Figure 4. More flux density is retained afterthe force has stopped. These "square loop" materials arebetter for use in magnetic memories.

Incidentally, a sinusoidal magne-tizing force isn't easy to obtain, be-cause it's difficult to cause a puresinewave of current to flow throughan inductance that has an ironcore. Remember that the amount offlux determines the reluctance ofthe iron core. So, as the sinewave ofcurrent starts to peak, it becomesmore difficult to establish flux inthe iron. Therefore, the countervoltage varies as the currentchanges for the minimum value tothe peak value. It is difficult, butpossible, to produce a sinusoidalmagnetizing force, but the currentmust be non -sinusoidal.

The graphs in Figure 4 are calledB -H curves, because they are plotsof flux density (B) versus magneticintensity (H). By using these twoitems, you always can obtain thesame curve for any given material.On the other hand, a plot of MMF

B

PULSES AND "SQUARE LOOP"MATERIALS CAN BE A

MEMORY UNIT

H

B -H

CURVE

INPUT

PULSE

Figure 6 One peak of a sine wave, or a DCpulse, can leave an appreciable amount ofresidual magnetism after the pulse is over.With some means of detecting the residualmagnetism, this can be the basis for amagnetic memory.

O

O

O


0

0

0

0

versus flux would vary according tothe length of the coil or the cross-sectional area of the magneticmaterial. Clearly, a B -H curve issuperior to others.

Magnetic StorageThis information has been giving

you the background for a discus-sion of magnetic materials that canperform as storage devices.

When a magnetic material has anearly square loop (as shown inFigure 5), it will retain a largeamount of residual magpetism afterjust one-half cycle of magnetizingforce (see Figure 6).

In other words, the magneticmaterial has stored magnetism ob-tained from an input pulse! Thinkabout the implications for a mo-ment. Digital signals are made upof highs and lows; that is, pulses orno pulses.

Therefore, if there were a way todetermine that a certain area ofmagnetic material retained magne-tism, then it would prove that ahigh pulse had been there. A lackof retained magnetism indicates alow was the last signal state.

In other words, the problem is tomove the digital information into orout of storage. Next month, I'llshow you how it's done.

Diode ProtectionRecitifier diodes sometimes are

connected in series to obtain a

Figure 7 Resistances and capacitancesparalleled across each diode of anarray help prevent the overload ofdiodes having different characteristics.Thus, diode failures are minimized.

higher total peak -inverse voltagerating (see Figure 7).

When a high reverse voltage isapplied to any diode, a minimumor small amount of current flows.With series diodes, the inversevoltages will be different acrosseach individual diode, because ofnon -identical reverse leakages.When this unbalanced condition ofthe voltages is excessive, the PIV

rating of one diode can be ex-ceeded, thus the diode fails byshorting.

In Figure 7, all resistors that areconnected in parallel with diodeshave the same value, so theyequalize the various diode reversevoltages.

Usually, the reason for the paral-leling capacitors is stated as an


OV

OV

OV

OVcf

rAPPLIED VOLTAGE

VOLTAGE ACROSS X,

VOLTAGE ACROSS X2

VOLTAGE ACROSS X,

Figure 8 For a brief time following the end of conduction, a diode has zeroresistance. This allows part of the reverse peak to appear in the outputwaveform. This time is called "recovery time," and it is different forindividual diodes. The diode having the shortest recovery time has the totalreverse voltage across it, during its recovery time.

OV

OV

OV

OV

F- APPLIED VOLTAGE

VOLTAGE ACROSS X,

VOLTAGE ACROSS X2

VOLTAGE ACROSS X3

X,

R[

Figure 9 Adding a capacitance across each diode lengthens the recoverytime of each one, thus minimizing the variations of recovery time, andprotecting most diodes from overvoltage shorts.

July, 1978 41

Technical Notebookcontinued from page 41

equalizing of the transient voltagesacross the diodes. When a diode isnon -conducting from a reverse bias,it acts as a capacitor. Therefore,the diode junction having thesmallest value of capacitance willhave the largest relative voltageacross it. Placing a capacitor inparallel with each diode then mini-mizes any differences of diodejunction capacitance.

These reasons undoubtedly arevalid, but there seems to be anotherreason for the capacitors.

Recovery timeWhen a diode conducts in the

forward direction, it has a largenumber of charge carriers in the Nand P regions. Then, when thevoltage across the junction is re-versed rapidly, a short period oftime is required for the chargecarriers to move out of the semi-conductor regions.

The effect of these stored chargecarriers is to reduce the reverseresistance to a low value for a briefperiod of time (called the recoverytime, or storage time).

In Figure 8, the unequal recoverytimes for three diodes in series areshown by a drawing, with therecovery periods shaded.

When the supply voltage first isreversed from forward bias to

reverse bias, the voltage across eachdiode remains at approximatelyzero volts, because the resistance islow while the charge carriers arebeing swept out. In this case, diodeX3 recovers first. So, for a veryshort period of time, all of thereverse voltage appears across it!Such a voltage overload coulddestroy X3.

Paralleling capacitorsAddition of a capacitor in paral-

lel with each diode lengthens therecovery times (see Figure 9).Thus, the differences between thevarious recovery times are reduced.Note that diode X3 has only part ofthe input voltage across it beforediodes X1 and X2 begin to conduct.This reduces the possibility of diodedestruction.

Anytime you replace just onediode in a series, you should checkthe paralleling capacitors and resis-tors. An open component mighthave caused the diode to fail.

Proper capacityThe proper value for the capaci-

tors of Figure 7 can be calculatedby the formula:

Shunt Capacitance = TsXnRT

SQUARE WAVE

GENERATOR

Figure 10 Connect the scope and components as shown, tomeasure the current caused by the diode recovery time.Spread the waveform by using a triggered scope.

Where: Ts is the storage time inseconds

n is the number of diodesseries

RT is the internal resis-tance of the power supplyplus the load resistance

Use the test setup of Figure 10 tomeasure the recovery time. The10 -ohm resistor allows the scope todisplay the diode current waveform.A good triggered -sweep scope witha wide bandwidth is needed toproduce a waveform similar to thatin Figure 11. By definition, therecovery time is the measured timebetween maximum negative currentand 10% of the negative current.This curve is surprising because itshows that the diode does notremove the negative half cyclecompletely, as is commonly be-lieved. However, the recoveryperiod is short, and some scopesprobably can't reveal it.

Proper resistanceThe optimum paralleling resis-

tance for each diode of a series isdetermined by the "rule -of -thumb"that says each resistor should beone-half the minimum value of thediode's reverse resistance.

OV

FORWARDCURRENT

REVERSE

CURRENT90%of

MAXIMUM

- RECOVERY TIME

Figure 11 Expect this kind of waveform from themeasurement of Figure 10. Repeat the test withpower -supply diodes, fast -recovery diodes used in scanrectification, and video -detector diodes. Usually, power -supply diodes show the longest recovery times.

O

O

O

(Th

42ELECTRONIC SERVICING

Servicing Betamax Videotape Recorders

By Harry Kybett

Recording andPlaying Chroma

F-CCQ

None of the home -type videocas-sette machines record and play thedirect NTSC color signals. Instead,the chroma and luminance com-ponents are separated and pro-cessed separately. Monochrome re-cording and playback were de-scribed in the past two articles. Thegeneral principles of the recordingand playback of chroma are givenfirst this month, followed by speci-fic Betamax operations. Trouble-shooting tips are supplied at theend.

Broadcast VTRsLarge VTRs used in broadcasting

studios have fast writing speedsproduced by either four rotatingheads or a large -sized helical drum.Therefore, these machines can re-cord and play the NTSC-type ofinterleaved color -and -luminance vi-deo signal without separation of theluminance and chroma portions.Even so, they have some time -baseerrors that require expensive elec-tronic correction to produce goodstable color during playback.

Attempting to record and playthe NTSC color/luminance videosignal using the low writing speedsof small helical machines wouldproduce unacceptable timing errorsfor the chroma part of the signal.

Another method must be used.

General ChromaRecording Operations

In small helical tape recorders,the chroma and luminance com-

ponents are separated, the chromais changed to a low frequency, andboth the chroma and the lumi-nance -modulated FM signal arerecorded together.

Separate filters (see Figure 1)

divide the NTSC input video intotwo basic components. One filterpasses the 3.58 -MHz signals, whileeliminating the luminance portion.The other passes the luminance,but eliminates the 3.58 -MHzchroma. The luminance video isapplied to the FM modulator, asexplained in previous months.

The chroma signal is processedby an AGC circuit that maintains aconstant chroma level, and then it'sheterodyned in a balanced modul-ator against a continuous carrier(usually 4.27 MHz) from a stablecrystal oscillator. The original twoinput frequencies and two sum -and -difference products appear atthe output of the balanced mod-ulator, but a low-pass filter elimi-nates all except the difference fre-quency of 688 KHz. This new688-KHz chroma signal has all ofthe phase and amplitude charac-teristics of the original 3.58 -MHzchroma signal, and it then isrecorded by adding it to theluminance FM carrier (the lumi-nance FM signal acts as a record-

ing bias for the chroma signal; thisis similar to the bias and signalmethod of recording audio).

General ChromaPlayback Operations

The playback chroma/luminance-FM signal at the output of thepre -amps is split, with one branchgoing to the luminance -demodula-tion chain, where the limitersremove the amplitude modulationof the chroma signal. Thus, thechroma signal is removed from theluminance -FM signal.

The other branch (Figure 2) hasa low-pass filter which removes theluminance -FM signal, leaving the688-KHz chroma signal.

Following the AGC correction,688-KHz chroma is heterodynedagainst the same 4.27 -MHz carrier(that was used during recording),and a bandpass filter extracts the3.58 -MHz difference frequency. Theup -converted color now is added tothe demodulated luminance signal,forming a NTSC signal at the videooutput of the machine.

Although, this heterodyne processenables the color to be recordedand adequately played back using alow writing speed and a low FMfrequency, it does not avoid the


Figure 1

VIDEO lb

FILTER TO

REMOVE 3 58MHz

BAND

PASS

FILTER

TO

LUMINANCE

CIRCUIT

58MHzCHROMA

AGC

SEPARATING THE CHROMAFOR RECORDING

LOW PASS

FILTER

688 kHzr CHROMA

SIGNAL

SUM AND DIFFERENCEFREQUENCIES

BALANCED

MODULATOR

4.27 MHzOSCILLATOR

July, 1978 45

Betamaxcontinued from page 45

time -base errors. It does, however,allow a method of correcting for thetime -base errors in the playbackchroma signal, thus providing acolor picture with stable tint andcolor level.

Typical Color CorrectionIf the same time -base error

occurs to both the down -convertedchroma playback signal and the4.27 -MHz heterodyning carrier, thetwo errors cancel, allowing thedifference frequency to have theidentical 3.58 -MHz signal that waspresent before the recording.

For example, assume that a

certain time -base error increasesthe frequency of the 688-KHzplayback chroma signal by 1 KHz(up to 689 KHz). After up -conver-ting by the 4.27 -MHz unchangedcarrier, the resulting chroma signalwould be 3.581 MHz. This is 1

KHz too high, which would causewrong colors. (These are the usualround numbers.)

However, if the 688-KHz signalwas increased by 1 KHz, and the4.27 -MHz signal also was increasedby 1 KHz, the resulting up -con-verted heterodyned chroma signalwould be 3.58 MHz, which wouldgive correct color.

The trick is finding a way tointroduce the same frequency errorsthat the 688-KHz chroma has into

_41PLAYBACK

VIDEO

LOWPASS

FILTER

688kHzCHROMA

AGC

4 27 MHz CORRECTION

OSCILLATOR CONTROL

AMP

BALANCED

MODULATOR

DETECTOR

BANDPASSFILTER

CONVERTING PLAYBACK

CHROMA

BURST

GATE

Figure 2

PLAYBACK

HORIZ SYNC

358 MHzCHROMA

the 4.27 -MHz carrier, and to makethe correction operate automati-cally. Fdrtunately, the method isnot very complicated.

In a helical VTR, these timingerrors change only a little withineach horizontal line. And, theerrors between one horizontal lineand the next can be identifiedeasily by comparing playback hori-zontal sync with stable horizontalsync, or a stable oscillator of thesame frequency.

If a stable oscillator is used tosupply one input of a comparator,and playback sync is fed to theother input, then the DC outputfrom the comparator will vary instep with any timing changes of theplayback sync.

Variations of the DC comparatoroutput voltage can be used toindicate the severity of the playbacksync -timing errors. In addition, thevarying DC voltage can be used tocontrol the frequency of the play-back 4.27 -MHz oscillator, so thefrequency variation is identical tothat of the 688-KHz chroma duringplayback. This fulfills the condi-tions given before for automaticcancellation of the time -base errorfor playback chroma.

Heterodyne correction of theeffects of time -base errors workswell, giving a stable picture on mostTV receivers. Note that the hetero-dyning correction applies only tothe color. The luminance time -baseerrors are not corrected; these must

VIDEO

3.58 -MHzCHROMAPIN 13

BANDPASS

FILTER

CONTROL

COLOR +4VMONO 08

CHROMA FOR BETAMAXRECORDING

TEST

POINTPIN 18

4.27 MHzOSCILLATOR

1-PIN 16

FREQUENCY

CONVERTER

PIN 15

AGC

DCv

CO' DR

NC FR

DCV

DELAYEDBURST

HORIZ SYNCGATE

PIN 10

DC

AMPLIFIER

3. 8MHz 1PIN 8BURST

CRYSTAL

FILTER

CONTINUOUS

CARRIERPIN 6

ACC

D;1.1 -

3.58MHzAMPLIFIER

LOW-PASS 688kHzFILTER CHROMA

ADDED TO

LUMINANCE

DURING RECORDING

Figure 3


be smoothed out by fast reaction ofthe horizontal AFC in the receiver.

DisadvantageThe main disadvantage of the

heterodyne-or "color under"-process is that the timing relation-ship between the sync pulses andburst is lost. Such systems some-times are called "non -phase" color.Note, that this is not true of Beta -max.

Betamax Color RecordingAlthough the Betamax color -re-

cording system is similar to theheterodyne correction just described,it contains two major improvements: The 688-KHz chroma signal isphase -locked to the incoming hori-zontal sync. This makes correctionof the color timing errors easier. The phase of the 688-KHz chro-ma signal is reversed during alter-nate tracks, where the "A" head isrecording. The phase reversal tendsto cancel the color crosstalk fromthose adjacent tracks.

A block diagram of the Betamaxrecording is shown in Figure 3. Abandpass filter rejects the lumi-nance component, accepts the 3.58 -MHz chroma frequencies, and sendsthem to an AGC amplifier. (Asdescribed before, the luminancechannel has a low-pass filter toremove the chroma signal.)

Output of the AGC amplifiergoes to the burst gate and to aheterodyne frequency converter,along with the 4.27 -MHz signalfrom an oscillator. From the fre-quency converter come four fre-quencies, and a low-pass filterremoves all except the 688-KHzsignal, which is added resistively tothe FM carrier at the heads, and isrecorded on the tape.

Processing the 4.27 -MHz carrierWe will concentrate now on how

the 4.27 -MHz carrier is formed,and why it is controlled differentlyduring recording and playback.This is the area where Betamax isnot like the other helical machines.

In general, the phase of thechroma signal is reversed duringthe recording of alternate tracksacross the tape. During playback,the chroma phase again is reversed.So overall, the chroma is correct,but the crosstalk between the tracksis largely cancelled.

Specifically, when the "B" head

HORIZ

SYNC

PG

PULSES

HORIZ

SYNC

Figure 4

FLIP

FLOP

PHASE LOCKED

LOOP

PIN 6

PIN 8

11015

4 27MHzTO FREQ CONVERTER

IC1007PIN NUMBERS

k 4 27MHz

692kHzFREQ

CONVERTER

3 57MHz

PRODUCING THE 4.27 -MHz

CARRIER

3.57 -MHz

OSCILLATOR

is recording, the 688 -MHz chromahas normal NTSC phasing. Duringtimes the "A" head is recording,however, the chroma phase isreversed. Notice that the chromasignal itself is not inverted, but thephase of the 4.27 -MHz heterodyn-ing oscillator is inverted, instead.

Figure 4 shows how the 4.27 -MHzcarrier is generated, then kept inphase -lock with the horizontal sync,and later the output is switched inphase. Crystal accuracy is needed,which is obtained by mixing to-gether the signal controlled by thehorizontal sync pulses (very stable)with a carrier from a crystal -con-trolled 3.57 -MHz oscillator.

Horizontal sync is the frequencystandard of a phase -locked loop,which is provided with a continu-ous -carrier output of about 692KHz. This carrier and the output ofa 3.57 -MHz (yes, 3.57-NOT 3.58!)crystal oscillator are inputs to aheterodyne frequency converter. The4.27 -MHz "sum" frequency is ap-plied to tuned transformer T1015.Electronic switching (controlled bya flip flop from the horizontal syncand the pulse -generator signal)alternately selects 180° signals fromthe transformer secondary (which iscentertapped, to provide bothphases).

In other words, the "A" positionof the electronic switch suppliesinverted 4.27 -MHz to the frequencyconverter that changes the chromato 688 KHz, while the "B" positionsupplies in -phase 4.27 -MHz to theconverter.

Therefore, the 688-KHz chromasignal that results from heterodyn-ing this phase -locked 4.27 -MHz

carrier with the NTSC 3.58 -MHzchroma is phase -locked to therecorded horizontal sync pulses.

Also, reversing the phase of the4.27 -MHz carrier also reverses thephase of the 688-KHz chroma-acharacteristic of heterodyning, andthe chroma crosstalk (which is nototherwise eliminated by the tiltedheads) is largely cancelled by theopposite phases.

The remainder of Figure 3 ismore routine. Burst is gated out ofthe 3.58 -MHz chroma by pulses ofhorizontal sync that have beendelayed in phase. (Videotape re-corders have no horizontal sweep orhigh voltage, as color -TV receiversdo, and the various gating pulsesare produced by delayed syncpulses.) A crystal filter is shockexcited by the burst, and it ringsuntil the next sync pulse gates moreburst. This produces a continuouscarrier at the burst frequency. Thecarrier amplitude is rectified, theoutput goes to a DC amplifier, andthen to the AGC stage to controlthe gain. In other words, the burstamplitude determines the chromalevel.

Part of the DC voltage from thechroma gain -control circuit triggersthe color -killer operation. If nocolor ,is present in the video inputsignal, the color killer shuts downthe frequency converter, and switch-es the other circuits into the mono-chrome mode.

NextIn the August issue, the coverage

begins with Betamax playback oper-ation, followed by chroma trouble-shooting.

July, 1978 47

aroducim 0

Dusting SprayChemtronics has introduced Mi-

cro -Duster, a new product for clean-ing and dusting delicate assemblieswith compressed gas. It can be usedfor dusting modules and circuitboards, electronic chassis, slides, orphotographic films.

MOISTURE FREENONTOXIC FILTERED CIASINSTANTLY REMOVES "IMMICROSCOPIC DUST AN. "

Micro -Duster contains a pure,moisture -free, non-flammable andnon-toxic filtered gas in an aerosolcan. A single 15 -ounce can providesmore than 1,800 one -second burstsof gas, or 25 to 30 minutes ofcontinuous dusting. Each can has a6 -inch extension tube for pinpointingthe blasts of gas.

Suggested retail price of Micro -Duster is $2.50


Semiconductor Handbook"Archer Semiconductor Reference

and Application Handbook" fromRadio Shack has cross-references ofArcher replacements for more than46,000 transistors, diodes, and othersolid-state devices.

In addition to the usual semi-conductor data, the handbook hascircuit diagrams of most of the ICslisted, schematics for all clock chipsand modules, and information aboutthe 8080A computer chip and theArcher line of display and opto-electronic devices.

Other sections have suggestionsfor the care and handling oftransistors, soldering precautions,case styles and dimensions, tips for

testing transistors, and a glossary.Price of the handbook is $1.95 at

all Radio Shack stores.Circle (17) on Reply Card

High -Voltage PuttyPremi-Putty from Oneida insulates

high voltage up to 40 KV, and it canbe used for repairing electricalwires, cables, or conduits; and forinsulating and sealing against water,oil, fumes, etc. The substance isresistant to the effects of highvoltages and ultra -violet light. Inaddition, it is a sound deadener. Itis available packaged in 15 -square -inch pieces, or by the spool inlarger quantities.


Replacement BalunsPTS Electronics is offering a new

card of seven replacement baluns infive different types. They are eitherexact replacements, or will replacealmost all baluns used in TVreceivers, antennas, MATV, orCATV systems. The card includesone extra of the two most frequent-ly -used baluns, and it sells todealers for $9.75 net. These re-placement baluns are available fromany of the 43 PTS Electronicsservicenters and stocking electronicparts distributors.

tint BALUNSCard of 7 °valet NET E9.75

PTS Iffi-

ertk


Mobile RadioThe Fleetcom II 520 UHF low -band

two-way mobile radio from theE. F. Johnson Company features 55watts of RF power over the range of

25-50 MHz. This radio providesreliable, long-range communications.All -solid-state circuitry offers lowcurrent drain with no warm-up timerequired. The 520 is said to be ahigh-performance radio with a sen-sitive receiver that provides goodadjacent channel and intermodula-tion rejection, for operation inRF-congested areas.

The Fleetcom II 520 has anoptional AC power supply so it alsocan be operated as a base stationwithout modification. Other optionsand accessories include two chan-nels; "Call Guard" tone squelch;remote -control systems; heavy-dutymicrophone; and various mounts.


Transistor Substitution ManualFuji-Svea Enterprise has published

a 90 -page Japanese Transistor Sub-stitution Manual which references3,000 transistors. The guide crossesJapanese -to -Japanese transistors inthe 2SA, 2SB, 2SC, and 2SD series.If a transistor is difficult to obtainor is discontinued, a substituteJapanese transistor is suggested.Most substitution guides cross Jap-anese numbers to American re-placements. This book fills the needfor Japanese -to -Japanese sub infor-mation which is usually hard tofind.

The book is available for $5.90plus $1.00 postage and handling; 85cents additional for COD.


CB TapeThe "CB trouble tape" by GC

Electronics fits all cassette players.It tells CB users how to isolate andeliminate most mobile and baseinterference. A pamphlet on varioustypes of interferences (and whichsuppressor to use) is included witheach tape.

A countertop merchandising pro-gram (17-250) with six troubletapes (18-250) on a POP easel isavailable. Suggested retail price ofindividual tapes is $4.95.


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


antenna systems Trx

UHF/VHF PreampBlonder -Tongue Lab's new Galaxy

series of preamps, which includesthe Voyager II 300 -ohm mastmounted UHF/VHF preamplifier, hasbeen introduced. '

The Voyager II is a solid-stateUHF/VHF all -channel preamplifierwith an indoor power supply andband separator. Separate UHF andVHF inputs are provided for indi-vidual UHF and VHF antennas. Thenoise figure of the Voyager II is saidto be equal to or better than that ofsolid-state TV sets, and greatlysuperior to tube -type TV sets. Mastmounting the Voyager II near theantenna, results in a significantreduction of snow on weak TVchannels. Four silicon transistorsare used in three independentamplifying sections. An accessoryband -separator facilitates connec-tions to the TV set input terminals.


CB AntennaThe "Intenna" by Microwave

Filter, utilizes a vehicle's metal frameas a slot -fed metal ground -planeantenna to provide high front -to -back ratio CB signal transmissionand reception. It mounts inside thevehicle, and is said to have from 3to 6 dB less noise pickup thanoutside vehicle antennas.

All components, including a tun-able matching section and 8 feet ofRG-58-U coax cable. are furnished.


CB AntennasChannel Master's Mag-Ne-Tenna

(model 5029A) and Adjustable Mag-Ne-Tenna (model 5030) CB antennasuse an in -line ferrite choke, mountedin the base housing, to stabilizeSWR, boost electronic efficiency,and enable the antennas to performbetter on vinyl -top cars.

Both antennas have epoxy -dipped,base -loaded coils, 24 -feet of coaxialcable, stainless -steel shock spring,and a high -capacitance stainless -steel whip.

The Adjustable Mag-Ne-Tennacomes with a universal balljoint thatallows vertical positioning for hatch-backs or cars with sharply -slopedtrunks.


Antenna -Rod CutterLarsen Electronics has developed anantenna -rod cutter with 9 -inchhandles and 18 -to -1 compound lever-age. The cutter allows cuts spaced1/8 -inch apart. The replaceableblades are made of Swedish toolsteel.


CB Co -Phase HarnessGC Electronics' CB Co -Phase Har-

ness is said to allow the cable to becut anywhere for two differentlengths and still maintain an im-pedance match. All wire leads areRG-58 and it is possible to transmitand receive if one antenna fails,gets damaged, or is lost.

The co -phase harness is availablein three models: Universal Kit18-392; RV Mirror Mounting Kit18-391; and Trunk Mounting Kit

18-393. Antenna connectors aresupplied with all kits.


MATV Mixer-SplitterThe model MM -2X2, by Extronix,

is a 4 -port hybrid mixer-splitter thatis said to save half of the signalpower required for a TV distribu-tion system by replacing two three -port hybrids.

EXTRONI XMIX -MATE

- MM -2X2

(i) D OUT C

The unit combines signals fromtwo sources and splits them into twomixed outputs, with typical loss of3.6 dB, isolation of 31 dB and returnloss of 23 dB, from 30 to 300 MHz.

Circle (Mon Reply Card

AM/FM/CB AntennaA manually -retractable AM/FM/

CB antenna, the CBA-12, is avail-able from Mura. Fully extended, the40 -inch antenna is adjustable forlowest SWR. The unit is centerloaded and corrosion resistant.

The antenna can be trunk orfender mounted and comes withkey, PL -259 connector and instruc-tions. Suggested list price is $29.95.



July, 1978 49

audio systems u f}

Microphone Floor StandsTwo new Atlas Sound Porta-

Series microphone floor stands com-bine base and tube in a single unit.Both stands have spring -action tele-scoping legs.

Model PS -C extends from thestandard 35 -inch height to a maxi-mum of 63 inches, and folds into a32 -inch length for transportation.

Model PS -C3 (especially designedfor use by seated performers or forinstrument-miking) extends from alow 26 inches to 66 inches in height.It telescopes to a minimum length of22 inches for shipping.


CB MicrophoneMura has introduced a CB noise -

cancelling power microphone. ModelPRX-NC is said to combine 12 dB ofnoise cancellation, 4 dB of PRMeffect, and 16 dB of variable gainfor a 15 -fold reduction of back-ground noise.

The single -cartridge ported designwas developed in conjunction withpolice -equipment manufacturersinterested in eliminating siren andPA background noise.

Maximum sensitivity is -50 dB,maximum gain is 16 dB, and theimpedance is 2500 ohms. Wired for

both relay and electronic switching,the mike is equipped with a variableslide -type gain control, a 9 -voltbattery, one 5 -foot coil cord, and afact sheet.

Suggested list price for the PRX-NC is $44.95.


Sealed Speaker SystemThe Magnum -800 from Argos

Sound is designed for continuousheavy-duty applications. The cabi-net is available in walnut or blackvinyl finish, and the 8 -inch twin -cone speaker is rated at 35 watts ofprogram signal and a responsebetween 60 Hz and 20 KHz.


Power BoosterA wide -range power amplifier by

Sparkomatic Corporation converts acar stereo or radio to a high -powersystem, that uses existing speakers.

The "on" position of model LC -50boosts power, while the "off" posi-tion connects the music sourcedirectly to the speakers.


Equalizer AmplifiersJandy International offers two

new Car-Fi products. Model 4200 isa stereo 7 -band graphic frequency-equalizer/preamp unit. Each equal-izer gives up to a 12 -dB boost or cutat 60 Hz, 150 Hz, 400 Hz, 1000 Hz,2500 Hz, 6000 Hz, and 15 KHz. Thefrequency response is rated at 10Hz to 35 KHz, and the signal-to-noise-ratio is said to be -85 dB. Abalance control, power switch, andseveral level controls are provided.

The suggested retail price is$89.95.

Model 310 has five bands ofgraphic equalization and a stereoamplifier rated at 30 watts -per -channel.


Folded -Horn Speaker SystemShowco Manufacturing is offering

Pyramid 900, a 3 -speaker systemwith a folded horn for the woofer,and front -mounted mid -range andtweeter speakers. These speakersprovide both direct and reflectedsound.

The system is said to providefaithful reproduction and high effi-ciency.


Cassette DeckA new stereo cassette tape deck,

featuring the exclusive Akai headfor record/playback and Dolby NoiseReduction circuitry, is being intro-duced by Akai America.

The new deck, model GXC-706D,is an amplifier -styled, four -track,two -channel, front -load stereo cas-sette deck that carries a suggestedretail price of $279.95.

The GXC-706D features large VUmeters for easy viewing duringrecording, a red panel light toindicate recording is in progress,and a three -digit tape counter. Leftand right channel mike input jacksand a stereo headphone jack arelocated on the front panel. The deckalso offers a locking pause controlfor recording convenience.

Powered by electronically -con-trolled DC motor, the tape deck usesintegrated GX glass and crystalferrite head for record/playbackand a separate erase head.




test equipment n

Analog MultimetersTwo new battery -operated analog

multimeters are offered by LeaderInstruments.

Model LT -70B features overloadprotection and polarity reversal, tenDC ranges from .25 to 1,000 volts,three AC ranges from 2.5 to 250volts, three DC current ranges, andone AC current range from zero to2.5 amperes. Two AA batteriesallow diode testing from 75 micro-amperes to 75 milliamperes.

Model LT -70B sells for $42.95,

complete with a set of heavy-dutytest leads and a set of alligator -clipadapters.

The companion model LV-71 hasdual-FET circuitry, a center -zeroscale on the 4.5 -inch taut -bandmeter, a polarity -reversal switch,battery -voltage test, and diode -typemeter -overload protection. Inputimpedance is 10 megohms for DCvolts and 1 megohm for AC. DCvoltage from 0.3 to 1,200 full-scaleis covered in 12 ranges, while 5ranges provide AC readings from 6to 600 volts. Four current rangescover from 0.3 milliampere to 300

IT'S NO PUZZLE TO ORDER

OELRICH SERVICE FORMSFOR TV-RAIIM 6 2 WAY RADIO SERVICE LEGAL FORMS FOR CALIF. FLA.UTAH NOW AT YOUR PARTS JOBBER OR WRITE FOR CATALOG 864

OELRICH PUBLICATIONS4040 N NASHVILLE AVE. CHICAGO. ILLINOIS 60634


NEW TUNERSNOT universal or customized. NOT seconds,culls, dogs, or oddballs. Only $24.95 for ANYnew tuner. Over 5,000 in stock including PhilcoTT192.

CALL TOLL FREE 1-800-433-7124TEXAS TUNER SUPPLY

4210 N.E.28th St., Ft. Worth, TX 76117

milliamperes, while resistances arechecked by 4 ranges from RX1 toRX1M. Decibels are measured intwo ranges from -20 to +17 dB or+ 15 to + 31 dB.

Priced at $69.95, model LV-71 ispowered by a 9 -volt battery, and issupplied with a set of test leadswith alligator adapters.


Oscilloscope Plug -InThe dual -trace SC 504 combines

with a selection of pulse generators,counters and other TM 500 instru-ments to form versatile instrumentconfigurations for measurements ondigital equipment. This new oscillo-scope plug-in from Tektronix furtherenhances the TM 500 family ofmodular test and measurement in-struments. Featuring 5 mV/div sen-sitivity at 80 MHz, this multimeteroffers a rear panel interface forinterconnecting the various instru-ments.

Enhanced auto triggering auto-matically increases the rang° of thetrigger level control for small signalsto make adjustment of the triggerpoint easy and precise. Trigger viewallows display of an external triggersignal and examination of its timerelationship to the two input chan-nels without changing any con-nections. Variable trigger holdoffmakes triggering solid and achiev-able on complex, asymmetric signalssuch as repetitive serial data wordsor double -pulse waveforms.


Wow and Flutter MeterFidelipac's wow and flutter meter

model 65-390 checks and expeditescorrection of periodic or cyclicalvariations in speed at high or lowrates in cartridge, reel-to-reel andcassette audiotape recorders; video-tape recorders; phonographs andturntables; and in film projectors.

This compact, lightweight, solid-state portable test instrument ac-curately measures the wow andflutter components in all types ofrecording and playback devices.Single meter readout indicates thedeviation from true speed of adevice within a 50/0 range by theuse of a zero -center drift meter.Also featured is an internal 3,150Hz reference oscillator, self-con-tained switchable weighting filterand a standard phone output jackfor oscilloscope connection. Allmetal interlocked construction as-sures immunity to EMI and RFI.


MultimeterModel 1350 from Data Precision is

designed for bench, service shop, orschool environments. This line -powered multimeter features a 0.43 -inch LED digital display.

Making use of LSI technology, this31/2 digit, full -function multimeteroffers 0.10/o basic accuracy. Thebench -operated unit measures DCvolts from +100 X to +1200 volts,AC volts from 100 X to a full 1000volts rms. Model 1350 will take+1200 VDC on any DC voltagerange continuously without loss ofcalibration, or will take a 6000 -voltspike on any voltage input for 500nswith no damage.

Model 1350 is housed in a casewith built-in carrying case handleand tilt stand, and sold completewith its own set of test leads, sparefuse, a full one-year warrantly,operator's and maintenance manual,and a certificate of conformancetracing its accuracy to NBS stand-ards. Recalibration is required atonly one-year intervals.




July, 1978 51

Wantedilimarketalace For Sale (Cont.)

Advertising 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 SaleREPLACEMENT COLOR YOKES -DEALERS ONLY.Zenith 95-2501-2532-2638-2667-S-89633 etc. 16.95,Magnavox 361380-1 18.95, Sylvania, GE etc. 14.95to 19.95. Request for price list on your Letter-head. David Sims Enterprises, Inc., 665 JerichoTurnpike, Huntington Station, N.Y. 11746.12-76-tf

TV & RADIO TUBES 36c EA!! Free color catalog.Cornell, 4221 University, San Diego, California92105. 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. ETC0-011, Box 762,Plattsburgh, N.Y. 12901. 6-78-tf

TUBES -RECEIVING, Industrial and Semiconduc-tors Factory Boxed. Free price sheet includingTV, Radio and audio parts list. Low, low prices.Transleteronic, Inc., 1365 39th St., Brooklyn,New York 11218. Telephone: (212) 633-2800. Tollf ree: 800-221-5802. 5-78-12t

NORTHERN CALIF. TV SALES & Service busi-ness. 12 years, top reputation. No real estateincl. Annual Sales $40,000. Main lines Zenith,RCA, Pioneer, Hitachi. Price includes lease, van,equip., etc. No other shops within 35 miles. Willconsider percentage with option for full timework. No window shoppers, please. Dick Murray,Box 816, Hayfork, CA 96041. 5-78-4t

SEEKING ORIGINAL JAPANESE TRANSISTORS,IC's, FET and diodes for CB, TV and stereorepair? See our full page ad in this issue forlisting of parts and prices. Write or call TOLLFREE for our complete list and compare prices.FUJI-SVEA ENTERPRISE, Dept. ES, P.O. Box30323, Cincinnati, OH 45240. Nationwide: (800)543-1607. Ohio: (800) 582-1630. 4-78-4t

TUNER SUB, $19.95, wired, tested, completewith batteries and ready to use on tube ortransistor sets. Tunes all VHF channels. This unitis without knobs or cabinet but very compactwith no wires or controls dangling. Easy to use,simply connect set's coax to sub and viewpicture (instructions provided). Only $19.95 andwe pay shipping or will ship C.O.D. ($1.85C.O.D. charge). Phone Toll Free 1-800-433-7124.This is not a gimmick. If not completelysatisfied, return within 10 days for full refund.TEXAS TUNER SUPPLY, 4210 N.E. 28th Street,Fort Worth, Texas 76117. 6-78-3t

TV BUSINESS 18 yrs. same location. Grossing90,000 +. Unlimited potential. Don Marble, CET.305-989-5070. 6-76-2t

COMPLETE COLOR B/W PICTURE TUBE Re-building Equipment, never used. Phone (212)387-2744. 616 Grand St., Brooklyn, N.Y. 11211.

6-78-2t

TV SALES & SERVICE -15 -year growing busi-ness, GE Dealership with room to expand,$30,000 1977 gross. Write to: Donald Lewis,Route 1, Central City, Neb. 68826. 7-78-2t

TEST EQUIPMENT and Technical Literature.Write for List: J. Criley, 633 Herman Road,Butler, Pa. 16001. 7-78-1t

B&K 415 "NEW" GENERATOR in original carton-complete $395.00. Wincharger-NEW-heavy

a duty 12 volt - 200 watt - wind generator with tenfoot tower - $395.00. Hickok 215 pocket semi-conductor tester -in carton - $69.00. L.R.E.HA -260 - 120 watt mobile 2 meter, linear amp. -$95.00. Precision E200C signal generator, used -$35.00. FRANCE -RADIO -ELECTRONICS, 14Broadway, Milford, CT 06460, (203) 878-4333.

7-78-1 t

HAVE SAM'S VOLS. 1-150 and Supreme1926-1942, also Zenith Service Manual Vo. 1 & 2.Will send copy of schematic you need for $2.312-546-2998. P. Casher, 117 E. Park Ave., RoundLake, IL 60073. 7-78-1t

UNIQUE EUROPEAN TYPE Home/Auto Alarm.Build your own. Complete schematic, descriptionand instructions. $2.00. F. W. Hughes, 6901 S.W.6th Street, Pembroke Pines, Florida 33023.7-78-1t

355 TUBES, 195 SAMS, Resistors , capacitors,some instruments and many many more items forradio and TV service or repair. $500.00 cash, youpay the freight. J. M. Hall, 215 N. Birdneck Rd.,Virginia Beach, VA 23451. Phone 804-422-4759.

7-78-1t

Professionals AccreditedPROFESSIONAL BACHELOR DEGREE...earnedwith 4 or more years of Electronic BusinessManagement, Sales, or Servicing Experience. ForFREE information write: EBERT PROFESSION-ALS INSTITUTE, Box 1651, Dept. R., Columbia,Missouri 62501. 5-78-6t

Business OpportunityTV TECHNICIAN! Increase your income up to$60,000 yearly. Rent -lease -sell TVs new -used,even from comfort of your home. Basic Prelimi-naries $4.00. Perry's TV Leasing, Box 1407, SantaMaria, CA 93456. 4-78-6t

SAVE HUNDREDS; dependable, quality Head -Ends, V/V, U/V Converters, Camera Modulators.Factory prices. Send $5.00 (or business card).Box 809, Boyton Beach, Fla. 33435. 6 -78 -9t -EOM

GET OUT OF THE TV RUT. Start making moneynow with Paltronix portable security systems. Notechnical hassles to keep up with. Full trainingprovided. Good margins to work with. Plus yourchance to diversify your services. For full detailscontact Don Musil, 48 West Golden Lake Rd.,Circle Pines, Minn. 55014. (612) 786-4244. 6-78-3t

ESTABILSHED TV SALES & SERVICE Businessfor sale In growth oriented city. Central Ohio.Business includes: attractive store room, currentInventory. Also exclusive TV Rental business.This is a substantial quality operation. Ownermay assist in purchase for right party. For moreinformation call or write Mr. Bruce Massa, P.O.Box 121, Reynoldsburg, OH 43068. Phone: (614)864-4363. 6-78-3t

MECHANICALLY INCLINED INDIVIDU-ALS -BUILD ELECTRONIC DEVICESIN YOUR HOME. GET STARTED INYOUR SPARE TIME. $300 TO $600/WKPOSSIBLE. EXPERIENCE NOT NECES-SARY. WRITE FOR FREE LITERA-TURE. ELECTRONIC DEVELOPMENTLAB., BOX 1535A, PINELLAS PARK,FLA., 33565.

8-78-tf

Education -InstructionREPAIR TV TUNERS -High Earnings. CompleteCourse Details, 12 Repair Tricks, Many Plans,Two Lessons, all for $2. Refundable. FrankBocek, Box 3236 Enterprise, Redding, Calif.96001. R-76-tf

INDUSTRIAL ELECTRONICS INSTRUCTOR -Teach theory and laboratory work. B.S. degree InElectrical Engineering. Master's degree prefer-able. Current industrial experience required.Teaching experience desirable. Position availableSeptember 1978. John C. Vander Molen, ActingDepartment Head, Ferris State College, BigRapids, MI 49307. An Equal Opportunity Affirma-tive Action Employer. 5-78-3t

EXPERIENCED TV TECHNICIAN WANTED. Grouphospital insurance, paid vacation, top wages.Call 509/586-4176 or send resume to Smitty's TV,114 W. Kennewick, Kennewick, WA 99336. 7-78-1t

Help WantedELECTRONIC TECHNICIANS -MOTOROLA, lead-er in two-way radio communication, presentlyhas openings throughout the U.S. for techniciansand supervisors experienced in the installationand maintenance of communications systems(two-way, paging, microwave and CCTV). Ifinterested in good salary and excellent fringebenefits send your resume and geographicalpreference to: BOB CLENDENIN, MOTOROLA,COMMUNICATIONS & ELECTRONICS, INC., 1821N. Office Square, Room 200C, Schaumburg, IL60196. Equal employment opportunity/affirmativeaction employer. 7-78-3t

advertiserrimAmerican Technology Corp. 7

B & K Precision, Dynascan Corp....29Dictaphone Corp 1

Dynascan Corp., B & K Precision . . .29

Fuji-Svea Enterprise 3

Gamit Enterprises, Inc 8

General Electric Co.,Tube Div. Inside Front Cover

Howard W. Sams & Co.,Inc Inside Back Cover

Master Applicance Corp. 25

NATESA 8

NESDA 7

Oelrich Publications 51

PTS Electronics, Inc. 17, 25

Raytheon Co. 5

Sencore, Inc. 2

Texas Tuner Supply 51

Winegard Co. 12-13

Zenith Radio Corp. Back Cover

RegionalAdvertising Sales Offices

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

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

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

LONDON, W.C. 2, ENGLANDJohn Ashcralt 8 Co., 12 Bear Street,Leicester Square; Phone: 930-0525

1171 VC-BADHOEVEDORp,HOLLANDJohn Ashcralt & Co., John J.Lucassen, Mgr., Sloterweg 303;Phone: 2968-6226

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


Sams has VCR'scovered

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Everything you have come to expectfrom Photofact® is now yours for video-cassette recorders. Helpful, reliablePhotofact information. Full photo cover-age for easy I.D. of all components andwiring. CurcuiTrace® testpoints andjunctions. Standard notation sche-matics. Parts lists showing exact re-placements. All mechanical and electri-cal adjustments. And more. Time savinginformation for servicing VCR's - to-day's growth product in electronics.

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Videocassette recorders are moving.Your customers have them. And Photo -fact has them covered. Sign up with yourSams Photofact distributor for your VCRseries today!

Howard W. Sams & Co., Inc.a subsidiary of ITT

4300 West 62nd Street/Indianapolis, Indiana 46206

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