pts electron - americanradiohistory.com · 2019-07-17 · pts electron precision tuner service pis...
TRANSCRIPT
PTS ELECTRONPrecision Tuner Service
PIS o announce theGRAND OPENING
of our new Service Centers in
LOf AfIGELECOLUMBUf, OHIO
PHOMIXBOJTOfl
flORFOLKMILWAUKEE
LET US TAKE CARE OF YOUR TUNER PROBLEMS . . .
PTS will repair any tuner-no matter how old or new. Fastest Service -8 hour-in and out the same dayOvernight transit to one of our strategically located plants. Best Quality-you and your customers are satisfied
PTS uses only ORIGINAL PARTS! No homemade or make -do, inferior merchandise (this is why we charg?,for major parts!). You get your tuner back in ORIGINAL EQUIPMENT condition.
PTS is recommended by more TV Manufacturers than any other tuner company and is overhauling more
PTS ELECTRONICS, INC.
VHF. UHF $10.95UV -COMBO 17.95IF-SUBCHASSIS 12.50
Major parts and shippingcharged at cost.
(Dealer net!)
HOME OFFICE BLOOMINGTON, INDIANA 47401 5233 S. Highway 37 Tel. 812-824-9331ALABAMA BIRMINGHAM, ALABAMA 35222 524 32nd St. So. Tel. 205-323-2657ARIZONA PHOENIX, ARIZONA 85061 2412 W. Indian School Rd. Tel. 602-279-8718CALIFORNIA LOS ANGELES, CA., Central 90023 4184 Pacific Way Tel. 213-266-3728
SACRAMENTO, CA., North 95841 4611 Auburn Blvd. Tel. 916-482-6220SAN DIEGO, CA., South 92105 5111 University Ave. Tel. 714-280-7070
COLORADO ARVADA, COLORADO 80001 4958 Allison St. Tel. 303-423-7080FLORIDA JACKSONVILLE, FLA., North 32210 1918 Blanding Blvd. Tel. 904.389-9952
MIAMI, FLA., South 33168 12934 N.W. 7th Ave. Tel. 305-685-9811INDIANA BLOOMINGTON, IND. 47401 5233 S. Highway 37 Tel. 812-824-9331KANSAS KANSAS CITY, KANSAS 66106 . 3116 Merriam Lane Tel. 913-831-1222_OUISIANA METAIRIE, LA. 70003 2914 Wytchwood Dr. Tel. 504-885-2349MARYLAND SILVER SPRINGS, MD. 20910 1105 Spring St. Tel. 301-565-0025MASSACHUSETTS SOMERVILLE, MASS. 02144 52 Holland St. Tel. 617-666-4770
SPRINGFIELD, MASS. 01103 191 Chestnut St. Tel. 413.734-2737MICHIGAN DETROIT, MICH. 48235 13709 W. 8 Mile Rd. Tel. 313-862-1783MINNESOTA MINNEAPOLIS, MINN. 55408 815 Lake St. Tel. 612-824-2333MISSOURI ST. LOUIS, MO. 63130 8456 Page Blvd. Tel. 314.428.1299MEW JERSEY E. PATERSON, NEW JERSEY 07407 158 Market St. Tel. 201-791-6380NEW YORK BUFFALO, NEW YORK 14212 993 Sycamore St. Tel. 716-891-4935NORTH CAROLINA CHARLOTTE, N. CAR. 28205 724 Seigle Ave. Tel. 704-332-8007OHIO CINCINNATI, OHIO 45215 8180 Vine St. Tel. 513-821-2298
COLUMBUS, OHIO 43227 4003 E. Livingston Ave. Tel. 614-237-3820PARMA, OHIO 44134 5682 State Rd. Tel. 216-845-4480
OKLAHOMA OKLAHOMA CITY, OK. 73106 3007 N. May Tel. 405-947-2013OREGON PORTLAND, OREGON 97213 5220 N.E. Sandy Blvd. Tel. 503-282-9636PENNSYLVANIA PITTSBURGH, PA. 15202 257 Riverview Ave. W. Tel. 412-761-7648
UPPER DARBY, PA. 19082 1742.44 State Rd. Tel. 215-352-6609TENNESSEE MEMPHIS, TENN. 38118 3614 Lamar Ave. ' Tel. 901-365-1918TEXAS HOUSTON. TEXAS 77032 4324-26 Telephone Ave. Tel. 713-644-6793
LONGVIEW, TEXAS 75601 Mopac Rd. Tel. 214-753-4334VIRGINIA NORFOLK, VA. 23504 3118 E. Princess Anne Rd. Tel. 804-625-2030WASHINGTON SEATTLE. WASH. 98108 432 Yale Ave. Tel. 206-623-2320WISCONSIN MILWAUKEE, WIS. 53215 3509 W. National Tel. 414-643-8800
We offer you finer, fastk,
I eTuner Service
16 ELECTRONICS, INC.......Number ONE and still trying harder!
(Not a Franchise Company)
1 YEAR
GUARANTEE
S
No
1...tor more details circle 119 on Reader Service Card
GTE Sylvania, Electronic Components Group, 100 First Avenue, Waltham, MA. 02154
The death ofa solid-state deviceneedn't complicate
your life.
You take a look at the job and the brandname's Bigston or Kobekiito or Teaberry orPace.
No problem!Sylvania replacement modules and IC's
fit these brands like a glove. They also fit over122 other brands, including RCA, Panasonic,Sony-and, of course, Sylvania.
For the vast majority of domestic andimported electronic equipment, all youneed is a basic stock of Sylvania ECGTM Semi-conductors. And our new Replacement Guideto show you which ones go where.
For a copy, see your Sylvania distributor.
We're helping you make it.enj SYLVANIA
Repair over 126domestic and importedbrands withSylvania modules and IC's.
JULY 1975, ELECTRONIC TECHNICIAN/DEALER / 1
J.W. PHIPPSEditor1 East First StreetDuluth, Minn. 55802(218) 727-8511
ALFRED A. MENEGUSPublisher757 Third AvenueNew York, N.Y. 10017(212) 754-4382
TOM GRENEYPublishing Director
JOSEPH ZAUHARManaging Editor
MARILYN MACDONALDProduction Manager
JOHN PASZAKGraphic Design
LILLIE PEARSONCirculation Fulfillment
GENE BAILEYManager, Reader Services
LOIS SANDERSPromotion Director
ROZ MARKHOUSEClassified Advertising Manager
CONTRIBUTING EDITORS
JOSEPH J. CARRBERNARD B. DAIEN
MANAGERS
DAVE HAGELIN43 East Ohio StreetChicago, III. 60611(312) 467-0670
CHUCK CUMMINGSAd Space South/West613 North O'ConnorIrving, Texas 75060(214) 253-8678
KEN JORDANDONALD D. HOUSTON1901 West 8th StreetLos Angeles, Calif. 90057(213) 483-8530
CHARLES S. HARRISONCY JOBSON57 Post StreetSan Francisco, Calif. 94104(415) 392-6794
ROBERT UPTONTokyo, JapanC.P.0 Box 1717
ELECTRONICTECHNICIAN/DEALER
July 1975 VOLUME 97 NUMBER 7
THE COVER: The variety of modern capacitors on this month's cover-which includepolarized and nonpolarized electrolytics, ceramics, micas, and polyester -and -polystyrene -film types-is evidence of the fact that advances in electronic technology inevitably lead tospecialization, proliferation and complexity of even a "standard" component such as thecapacitor. Although most advances in technology ultimately produce better performing,more reliable products, they also increase the knowledge and skill requirements ofservicers.
FEATURES
12 CAPACITORS-TYPES, CHARACTERISTICS AND APPLICATIONSShould you replace an electrolytic capacitor with an electrostatic type? How can yousatisfy particular capacitance and working voltage requirements if you can't obtain acapacitor with the needed ratings? Does a larger filter capacitor increase the peakoutput voltage of a power supply? What do the ratings "N750" and "NPO" mean?These and other questions about capacitor characteristics and replacement areanswered in this compendium of facts a service technician should consider whentesting and replacing capacitors. By Joseph Zauhar, ET/D Managing Editor.
20 "EXOTIC" SEMICONDUCTORS-THEORY & TESTINGTechnician -oriented explanations of the theory of operation of UJTs, Diacs, Triacs andSCRs, plus proven procedures for testing each. By Bernard B. Daien, ET/D Contribut-ing Editor.
28 POWERS, LOGS & dBS-A BRIEF REVIEWMost servicing technicians do not need these mathematical tools very often, but forthose infrequent occasions when they do this review of the fundamentals of powers often, common logarithms and decibels should ease the transistion from practicingtechnician to mathematician. By Jack Hobbs & J.W. Phipps.
34 POWER SUPPLY REGULATOR CIRCUITSThe theory of operation and procedures for servicing shunt -type, series -pass,combination and switching regulators. By Joseph J. Carr, ET/D Contributing Editor.
TEKFAX-Admiral color TV Ch. 4M10: Admiral b -w TV Ch. TL6; Magnavox color TVCh. T995: Panasonic color TV Model CT -324; and Trav-Ler b -w TV Ch. TR2-1A/2A.
DEPARTMENTS4 LETTERS 45 NEW PRODUCTS6 TECHNICAL LITERATURE 48 CLASSIFIED ADS9 NEWS OF THE INDUSTRY 50 ADVERTISERS' INDEX
40 TEST INSTRUMENT REPORT 51 READER SERVICE44 TECH DIGEST
MI A HARCOURT BRACE JOVANOVICH PUBLICATION "irp'
HARCOURT BRACE JOVANOVICH PUBLICATIONS. James Milholland, Jr.. Chairman, Robert L. Edgell. President. Lars Fladmark,Senior Vice President. Richard Moeller. Treasurer, John G Reynolds, Vice President. Thomas Greney, Vice President. EzraPincus. Vice President, Bruce B. Howat. Vice President, James Gherna. Vice President.
ELECTRONIC TECHNICIAN/DEALER is published monthly by Harcourt Brace Jovanovich Publications. Corporate offices, 757Third Avenue. New York, New York 10017. Advertising offices: 43 East Ohio Street. Chicago. Illinois 60611 and 757 ThirdAvenue. New York. New York 10017. Editorial. Accourting. Advertising Production and Circulation offices: 1 East First Street.Duluth. Minnesota 55802. Subscription rate: one year. $7: two years. $12. three years. $16 in the United States and CanadaOther countries one year. $15: two years. $24: three years. $30. Single copes: 75 c in the U.S. and Canada: all other countries:$2. Second Class postage paid at Duluth. Minnesota 55806 and at additional mailing offices. Copyright 1975 by HarcourtBrace Jovanovich. Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by anymeans, electronic or mechanical, including photocopy. recording, or any information storage and retrieval system. withoutpermission in writing from the publisher.
POSTMASTER Send Form 3579 to ELECTRONIC TECHNICIAN/DEALER. P.0 Box 6016, Duluth. Minnesota 55806
2 / ELECTRONIC TECHNICIAN/DEALER, JULY 1975
A NEW DIMENSIONhas beenadded to
professionakcolor TVservicing
Thenew
CNROMA
hroma-Line
V1010
0
200
SOUND CARRIER
UNMOO
OFF
Chroma-LineCOLOR -PATTERNGENERATOR
For Faster, EasierColor TV Servicing
MOO.
C r Fatt rn Generat o - model 432CH 3
VIDEO
;OUND
4.5 MHz)
SIMPSON MVP C COMPANY ELGIN, LINOIS 80:20
Model 432
16 "touch command" patterns instantlyavailable in a 4 x 4 pushbutton matrix3 VHF channels: 3, 4 and 7, channels 3 and 4fully crystal controlled2 UHF channels: 23 and 52IF Output: 45.75 MHzComposite Video Output: Sync, patternand soundBuilt-in cable storage compartment
MODEL 432 Complete with two cableassemblies, for Coax and 300" inputs, andOperator's Manual $179.AVAILABLE NOW FROM ELECTRONIC PART DISTRIBUTORS
CH.4
CH.7
IF
45.75 MHz)
POWER
OFF till ON 40
This new Simpson model is an all solid-stateinstrumeit incorporating the latest digitalLSI and SSI technology for maximizedcolor -pattern stabi.ity and reliability. Today'sprofessional TV technicians will appreciateits many extra features and performancecharacteristics.
Sound Output: 4.5 MHz carrier, unmodulatedand 1000 Hz FM modulatedAdjustable RF, IF and Video signal level75 Coax and 300 'I Balun OutputsRed, Blue and Green bun killersTransformer -isolated, line powered, forinstant -ready use
FOR COMPLETE SPECIFICATIONS, WRITE FOR BULLETIN T829
SIMPSON ELECTRIC COMPANv853 Dundee Avenue, Elgin, Illinois 60120(312) 697-2260 Telex: 72-2416 Cable: SIMELCO
...for more details circle 123 on Reader Service Card
14WV,INS
WMi %
JULY 1975, ELECTRONIC TECHNICIAN/DEALER / 3
346 WaysTo Save OnInstruments!EICO's Test Instruments lineis the industry's mostcomprehensive because eachinstrument serves a specificgroup of professional needs.You name the requirement-from a resistance box to aVTVM, from a signal tracer toa scope, from a tube tester toa color TV generator, etc., youcan depend on EICO to giveyou the best professionalvalue. Compare our latestsolid state instruments at yourlocal EICO ElectronicsDistributor, he knows yourneeds best-and serves yourrequirements with the bestvalues!
"Build -it -Yourself" and saveup to 50% with our famouselectronic kits.For latest EICO Catalog on TestInstruments. Automotive and HobbyElectronics. Eicocraft Project kits.Burglar -Fire Alarm Systems and nameof nearest EICO Distributor. check readerservice card or send 50c for fast firstclass mail service.
EICO-283 Malta Street,Brooklyn, N.Y. 1120730 years of service to the ProfessionalServiceman.
EICO...for more details circle 106 on Reader Service Card
4 / ELECTRONIC TECHNICIAN/DEALER, JULY 1975
LETTERS
Sources of Information About TVReceivers Sold In Canada
In the Letters department of theMarch 1975 issue of ET/D, Mr. Ruhdescribed the difficulty he had in ob-taining service information and partsfor an AGS TV receiver.
Service data for AGS and most otherTV receivers sold here in Canada canbe obtained from the following source:
RCC Publications461 King St., W.Toronto, Canada M5V 1K8
Other ET/D readers might be in-terested in also learning about the fol-lowing Canadian company whichmarkets a line of replacement parts(tradename ELCOM) for TV receiversmanufactured in Canada:
Lake Engineering Co., Ltd.123 Manville Rd.Scarborough, Ontario
I also want to point out that somereceivers manufactured in Canada bysubsidiaries of U.S. companies are notidentical to the same models manufac-tured in the U.S.
Charles CalvertRadio College Of CanadaToronto, Canada
Mr. P.M. Leyden of St. Catharines,Ontario also sent us the same informa-tion about sources of data forCanadian -built TV receivers. A warm"thanks" to both of these helpfulneighbors up North.-The Editor
Another Formula For ComputingRequired Service Labor Income
With reference to Table 2 in the ar-ticle titled Profitable and CompetitivePricing of Service Labor (page 12, De-cember 1974 ET/D), I would like tosuggest the following simple formulafor calculating the gross service laborincome:Selling Total CostsPrice = 100% - Desired % of Profit
(expressed as a decimal)This formula is widely used in busi-
ness and has the advantage that it canbe used to calculate any desired per-centage of profit. For example, usingthis formula and figures in Table 2:
Gross Service Labor Income =$ 93,784
100% - 20% -$93,784_ $117,2300.8
For a 10 -percent profit the divisorwould be 0.9, and for a 25 -percent pro-fit it would be 0.78, etc.
James M. WillisTexarkana, Texas
ShhhhhhLet's
have itQuiet!
QUIETROT.tt IL It 1. II
,SPRAY -PACKtUBRI-CLEANiR
ForTV TUNERS, SWITCHES,
ti3NTROLS, POTS., RELAYS,ETC14SUREs ER AND
:IFGNEST MAN:iCOLOR AN') h. AND Yr'll, ,f iA*5
"IINALly No: ,t:C ,;ROS1,1
4A1MkFV,EFFic
CAUTION
NET WT. 6 OZ.
Let's cut out the noise fromradio, TV and instrumenttuners, switches, relays, poten-tiometers, slides and othercontrols. Quietrole electroniccleaners and lubricants willcut through all that grit andcrud to banish squeaks, rasps,scratches and whines. Yetthey'll not harm plastics ormetal. Non -inflammable, non-corrosive, non-conductive,with zero effects on capacityand resistance. Quietrole -inspray cans or in eye -dropperbottles. A good way to build ahappier (and bigger) clientele.Buy them from practically anyleading jobber or distributor
Product of
QUIETROLECOMPANY
Spartanburg, South Carolina
._for more details circle 120 on Reader Service Card
RCA Solid State, Box 3200, Somerville. N.J. 08876.
K.Ca ieves
Fix it with SK.The RCA quality replacement.
Count on top quality in SK replacement semi-conductors. Because they carry the name RCA, a topmanufacturer of OEM devices. Same strict AQL stan-dards, same strict Director of Quality Assurance. That'show we protect you from callbacks, soyou can make more profitable use of yourtime. RCA's higher -than -ever 410 to 1replacement ratio will help you save timetoo. Your key to fast, easy replacement is er
RCA's new 1975 SK Replacement Guide.Get your copy at the RCA distributorwhere you buy SK parts. SK 3092 eible &Ar Diode
DEXC.IE pee) or,
1111111.1
isa ".7
SS.cuTimIgTAZ
It's OK if it's sk
...for more details circle 121 on Reader Service Card
JULY 1975, ELECTRONIC TECHNICIAN/DEALER / 5
TECHNICALLITERATURE
Thyristor/Rectifier DirectoryA 68 - page, pocket - size directory
describing over 500 RCA thyristorsand rectifiers is now available. TheThyristor/Rectifier Pocket Directory,TRP - 440A, tabulates the thyristors(SCR's, ITR's, and triacs), discs, andrectifiers available from RCA, andclassifies these devices according tovoltage and current ratings, gate
charateristics and package styles.Also included are type - number cross -reference information for RCA's newdevice numbering system, applica-tions information charts and a list ofRCA sales offices and distributors.RCA Solid - State Division, Box 3200,Somerville, NJ. 08876.
Signal Source Test Instruments
A new, 6 - page, fold - out, short -form catalog is available describing 31different models of signal source in-struments which include: functiongenerators, phase generator, fre-quency synthesizers, and complex -
WHEN YOU'VE GOTSOLID STATE SENSITIVITY
IN A 5" GENERAL SERVICESCOPE WI1H
&TV -H... YOU'VE GOT
;'
LEADER .
c
e
(910
What's more, the LBO -511 delivers calibratedvertical input along with rock -like stability,recurrent sweep and automatic synchronization.This outstanding wideband oscilloscope:vec-torscope is the newest in a series of solid stateinstruments, Leader developed to give you morefor your money. Sweep frequency is in 4 rangesfrom 10Hz to 100Hz and we've added a versatilephasing control, continuous from 0 to 140 .
Overall sensitivity is 20mVp-p cm to 10Vp-p cm
o
and vertical input is calibrated. The solid-statestability and distortion -free displays are theresult of Leader's exclusive FET input stages plusDC coupling and push-pull amplifiers. Bandwidthis DC to 10MHz. And, there are special inputs toobtain vectored pattern displays for color TV cir-cuit testing. Complete with probe, adapter andtest leads, the LB0511 weighs just 15 lbs. andis unusually compact.
"Put us to the test"
$299.as
LEADER151 Dupont Street, Plainview, L.I., N.Y. 11803 (516) 822-9300INSTRUMENTS CORP
...for more details circle 116 on Reader Service Card
6 / ELECTRONIC TECHNICIAN/DEALER, JULY 1975
waveform synthesizers. This catalogalso contains a model capability cross -reference chart and prices. Exact Elec-tronics, Inc., Box 160, Hillsboro, OR.97123.
Test Equipment
A 16 - page catalog covers a varietyof test equipment, including two newVOM's - the Model 310, Type 3 andthe Model 615. The catalog, No. 60 - T,covers Triplett's full range of productsfrom general, multi - purpose VOM'sthrough laboratory and special fea-tures testers temperature testers andaccessories. It contains a handy selec-tion guide chart, designed to helpselect a tester for specific require-ments, and lists both sales representa-tives and service modifications cen-ters. Dept. PR, Triplett Corp.,Bluffton, Ohio 45817.
Che-nical Products
A new 12 - page catalog of chemicalproducts made exclusively for the elec-tronics industry is now available. Thecatalog features application informa-tion, photos, descriptions, and specifi-cations on chemicals used to speedelectronic servicing and facilitatemaintenance of electronic equipment.Included are tuner sprays, contactcleaners and lubricants, circuit cool-ers, insulating sprays, lubricants,moisture removers and heat sink com-pounds. Chemtronics Inc., 1260 RalphAve., Brooklyn, NY.
Electrical Maintenance Hints
A new hardbound edition of theWestinghouse Electrical MaintenanceHints handbook is now available. The1,450 - page manual is designed toprovide plant maintenance personnelwith a convenient reference source onmaintenance practices for the mostcommonly used types of electrical ap-paratus. It contains 46 chapters, eachorganized to help the user quickly lo-cate any particular subject. Eachchapter is indexed by topic and sub -topics, which eliminates the need tocompletely read or review the entirechapter to obtain information on aspecific subject. It also contains photo-graphs, diagrams, charts, tables andtest procedures. Price is $15.Westinghouse Electric Corp., PrintingDivision, P.O. Box 398, Trafford, PA.15085.
Electronic Parts Catalog
A 32 - page 100 AnniversaryCatalog featuring a beat inflationsales of electronic parts is available.For your free catalog, write to B&FEnterprises, 119 Foster Street, Pea-body, MA. 01960.0
Type EVthe space -saver lytic 0.001)0,0.0.0000 0.i)
board roomFor space -saving lytic capacitor replacements on crowded printedwiring boards found in most of today's foreign and domestic consumerentertainment products, Sprague Type EV Verti-Lytic® Capacitors havethe widest range of values . . . in the smallest case sizes . . . of anysingle -ended capacitors available anywhere!
Get on Board with the KE-17 AssortmentThis handy assortment of 61 Type EV Capacitors in the 27 most -popular ratings gives you an on -the -spot inventory of thereplacement capacitors you need for most of the sets you'llencounter. Sturdy blue plastic cabinet has nine pre -labeleddrawers for fast, easy selection. And you pay for capacitors only... the cabinet is yours at no extra cost!
See these "new era" capacitors at your Spraguedistributor's. Or, get the full story by writing forBrochure M-951 to: Sprague Products Co., 65 MarshallStreet, North Adams, Mass. 01247.
6S 2114
THE BROAD LINE PRODUCER OF ELECTRONIC PARTS...for more details circle 124 on Reader Service Card
JJLY 1975, ELECTRONIC TECHNICIAN/DEALER 17
SPRAGUE®THE MARK OF RELIABILITY
9 new ways to improve tv receptionand your profit -picture.
Whether its a 1000 -set installation at the International Hotel in Las Vegas... or a basic 4 -set home TVsystem, there's a Blonder -Tongue MAN product that will deliver better TV reception.
Here are 9 new products backed by 25 years of experience in improving TV reception.
1 AB -300, 25dB gain C h 2-13, FM. Dual voltage power for short or long 25dB loss runs of 75 ohm or 3000 ohm
downlead.
2. DA8-T-famous DA8B fully transistorized. l'g13dB gain. Lower noise. 1 input/8 outputs. ei -VHF/FM. Universal 300 ohm/75 ohm.
3 DA-21-21dB gain, 75 ohm. VHF/ FM and all CATV channels to. 300 MHz.
4 Homer 375 Amplified Splitter-VHF/FM. and all CATV channels to 300 MHz. 3 sets300 ohms and one set at 75 ohms from aCATV cable input.
5 Vamp T-75 Mast -Mounted Preamp-17dB gain. PatentedM ICEF overload protection circuit. 6dB noise figure
75 ohm downlead 2-13.
6 CR-4-Deluxe compound, parallel -jawM crimping plier.
7 Model 4994-75 ohm 2 -way antenna switch. Video, VHF, FMand all CATV channels to 300 MHz.
8 4946 U/V/FM -An economical band separator for TV sets and an FM
takeoff connection.
9 SA -1000 Semi -automatic Rotor. Computer -age LED tuningM indicator. 360° rotation. Economical two -wire installation.
BLONDEFTrONGUEThese new BLONDER -TONGUE products are now at your distributor.
Blonder -Tongue Laboratories, Inc., One Jake Brown Road, Old Bridge, NewJersey 08857...tor more details circle 105 on Reader Service Card
8 / ELECTRONIC TECHNICIAN/DEALER. JULY 1975
NEWS OF THE INDUSTRY
July 15July 17July 28-29-30Aug. 26Aug. 28Sept. 8Sept. 10Sept. 11Sept.*Sept.*Oct.*Oct.*Oct. 21-22-23Nov. 11-12-13
GTE Sylvania Implements New Color TV Picture Tube Labeling System
A new, clearer method of identifying color TV picture tube types has been developedand implemented by the Electronic Components Group of GTE Sylvania.
Under the new system, the grade of the tube is printed clearly on the carton-either"ALL NEW," "NEW SCREEN & GUN" or "NEW GUN." A back-up color code is also usedon each carton, with red indicating "all new," blue indicating "new screen and gun," andgreen indicating "new gun." In addition, two type number prefixes, "AA" for "all new"and "A" for "new screen and gun," are included on the cartons of these types of tubes, toconform to California and Florida picture tube grading regulations.
Winegard MATV Field Training Schedule
The Commercial Products Division offollowing schedule of one- and three-day
Knoxville, Tenn.Dayton, OhioBurlington, Ia.Alexandria, Va.Orlando, Fla.Torrance, Calif.Anaheim, Calif.Tucson, Ariz.Boston -Portland, Mass.Gape Girardeau, Mo.Fargo, N.D.Minneapolis, Minn.Raleigh, N.C.
Fla.
the Winegard Company has announced theworkshop seminars on MATV.
Mr. Jim Williams (404) 469-3450Mr. Roger Good (614) 846-8449Mrs. Sandie Powell (319) 753-0121Mr. Dennis Williams (302) 834-8469Mr. Leo Riddle (813) 293-5070Mr. Ben Hedges (213) 772-1451Mr. Ben Hedges (213) 772-1451Mr. Ben Hedges (213) 772-1451Mr. Dave Johnson (603) 888-0323Mr. Jon Peterson (815) 459-8294Mr. John Jordahl (507) 332-8052Mr. John Jordahl (507) 332-8052Mr. Jim Williams (404) 469-3450Mr. Leo Riddle (813) 293-5070
*Specific date not yet determined but will be at least 45 days in advance.Advance registration for any of the preceding seminars can be made by contacting the
indicated District Manager or by calling James C. Banard, National Sales Manager,Commercial Products Division, Winegard Company, (319) 753-0121, or write him at3000 Kirkwood St., Burlington, Iowa 52601.
RCA, Zenith Presidents Report Increased Color TV Sales Late In 1st Half, Predict ThatUpward Trend Will Continue
RCA President Anthony L. Conrad and Zenith President John J. Nevin both havereported increases in color TV sales during the 2nd quarter, and both believe that thetrend will continue.
RCA's Conrad, speaking before the 56th Annual meeting of RCA shareholders in earlyMay, said that the depressed sales in the color TV industry-a principal cause of RCA'sfirst quarter earnings decline-had been improving in recent weeks, and then added,"The trend from here on should be upward."
Zenith's Nevin at about the same time said, "The worst of the sales decline is wellbehind us. There's no question that there's been a significant upturn of sales to dealers."
121 Million TV Sets In Use
As of 1974, there were 64 million monochrome and 57 million color TV receivers in usein the U.S.. or a total of 121 million TV receivers in use.
These and other statistics and facts about the electronic industry and the productswhich are produced, marketed and serviced by it are reported in the 120 -page 1975Electronic Market Data Book, recently released by the Electronic Industries Association(EIA). Copies of the book can be obtained by nonmembers for $20. Write: 1975 Elect. Mdt.Data Book, EIA, 2001 Eye St., N.W., Washington, D.C. 20006.
Pay TV To Spread By Satellite If FCC Approves
Home Box Office, Inc., a subsidiary of Time Inc., which since 1972 has been providingthe Northeastern States with a single channel of pay -TV programming, reportedly hasmade arrangements with RCA Global Communications for use of its satellite facilities toinitially distribute pay -TV programming to two community antenna TV (CATV) sys-tems in Florida, and eventually to other states in the West and Southwest.
If approved by the Federal Communications Commision (FCC), Home Box Office's planto distribute pay -TV via satellite could become operational as early as this October.
Initially, the pay -TV program will be sent from Home Box Office's central studio andtransmission control center in Manhattan to a satellite transmission system. The satel-
JULY 1975, ELECTRONIC TECHNICIAN/DEALER / 9
NEWS
lite pay -TV signal will be received by two separate receiving (earth) stations built inFlorida by two large CATV companies: American Television and Communications, andUA-Columbia Cablevision. The signals will then be distributed via microwave to cablesystems in Florida owned by these two companies, and to Florida cable systems owned byother companies.
Later (possibly as early as 1976), UA-Columbia Cablevision also will build earthstations for distribution of satellite pay -TV signals to its CATV systems in Arkansas,Texas, Arizona, California and Washington State.
Wisconsin Service Association Surveys The Incidence of TV Module Replacement
The Wisconsin Electronic Service Association (WESA) recently asked its members tolist the TV modules they replace most.
Following is a list of the modules (or panels) which WESA members say they replacedmost often, with the most frequently replaced under each brand listed first and the restlisted in descending order according to frequency of replacement:
Admiral: M-20 Ch, A8911-1; 3M20 Ch, A8912-2; M24 Ch, A8912-2, A8926-2; M-25Ch, A8919-1, A8920-1, A8921-1, A8923-4, A8924-1, A8926-4; M30 Ch, A8927-3, A8931-1, A8929-1
Motorola: CA, BA, JA, AZ, F(A), GA Philco: 69-1025, 69-1005, 69-1014RCA: 132-581, 132-582, 132-579,134-007, 138-697, 135-871, 133-455, 139-685,
133-563, 132-583, 132-580Sylvania: 02-375000-1,2,3 & 02-37503-1,2 and 3Zenith: 9-27, 9-37, 9-86, 9-87, 9-90, 9-92, 9-97. (Zenith ICs: 150-162, 150-186, 150-190,
221-43).
NATESA Convention August 7-10
The National Alliance of Television and Electronic Service Associations (NATESAwill hold its annual convention August 7-10 at Pheasant Run Resort in St. Charles,Ilinois.
Limousine service from Chicago's O'Hare Airport and the Chicago Loop to PheasantRun is available seven times per day.
The registration fee for the convention is $25.00 per person, and includes sponsoredmeals, refreshments, hospitality suites, banquet and floor show.
For more information about the NATESA Convention, write Frank Moch, NATESA,5908 S. Troy St., Chicago, Ill. 60629.
Washington and Oregon Associations Schedule Joint Convention July 25-27
The Washington State Electronics Council (WESC) and the Oregon Television ServiceAssociation (OTSA) are holding a joint convention July 25-27 at the Jantzen BeachThunderbird Motel in Portland, Oregon.
A two-day business management school will be presented by the Portland CommunityCollege during the convention.
The registration fee for the convention, including the business management school, is$60.00 for servicers and $30.00 for their wives.
More information about the joint convention can be obtained by calling James Rolison(503-282-7751) or Robert A. Villont (208-475-8300).
NESDA Convention August 12-17
The National Electronic Service Dealers Association (NESDA) will hold its annualconvention August 12-17 at the Hyatt House Hotel in Winston-Salem, North Carolina.Registration information can be obtained by writing: NESDA, 1715 Expo Lane, In-dianapolis, Ind. 46224, or phone (317) 241-8160.
PTS Opens New Tuner Service Centers In Ohio and Maryland
PTS Electronics, Inc., Indiana -based TV tuner repair company, recently announcedthe opening of two new service centers, one at 4005A E. Livingston, Columbus, Ohio43227, and 52 Holland St., Davis Square, Sommerville, Maryland 02144.
Senate Passes Consumer Agency Bill
The United States Senate on May 15 passed bill S.200, which, if subsequently passedby the House of Representatives, will create the Agency For Consumer Protection.0
10 / ELECTRONIC TECHNICIAN/DEALER, JULY 1975
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JULY 1975, ELECTRONIC TECHNICIAN/DEALER / 11
Capacitors Types,Characteristics and Applications
Electrostatic and electrolytic capacitors differnot only in their design and construction, but also in their
circuit applications. You should not attempt to replaceelectrostatic types with elect.-olytics and vice versa
Fig. 1-Two of the most commonly used types ofelectrolytic capacitors are the single -endprinted -circuit type shown on the lett in the photoand the tubular axial lead type shown to theright.
Servicing of the vast number ofconsumer home entertainmentelectronic products, both domesticand foreign, can create a problemof parts availability for the elec-tronic technician. Capacitors are agood example, and if the exact re-placement part is not always a-vailable, we must use the correctcapacitor type for the many criti-cal circuits. A better understand-ing of the various capacitor typescan eliminate future difficultiesand improve your effectivenessand profit.
There are many different typesof capacitors, which vary in shape,size and capacitance value. Wemust remember they all have beenconstructed for a specific applica-tion employing materials whichmake them superior to othercapacitors for the particular cir-cuit in which they are employed.
Capacitors can be placed intotwo categories and can be iden-tified as either an electrolytic orelectrostatic type. We must recog-nize what the basic differences arebetween the two capacitor types inboth construction and applica-tions.
ELECTROLYTIC CAPACITORS
Electrolytic capacitors willstore more electrical energy fortheir physical size than any othercapacitor. Instead of the usualplates separated by a dielectric ascompared to the electrostatic type,a very thin film of aluminum oxideis formed on the surface of analuminum anode functioning as adielectric and a liquid electrolyteforms the cathode. A secondmetallic conductor acts as the
By Joseph Zauhar
connection to the liquid cathodeproviding an external connection.
The aluminum and the tan-talum capacitors are two of themost common types found in homeentertainment products. They arebasically constructed in the samemanner, covering the aluminumor tantalum anode with an oxidefilm. The liquid or solid electrolyteis the cathode.
The aluminum -oxide provide avery high resistance to currentflow in one direction and a low re-sistance in the opposite direction.First, the film functions as adielectric and then the plate in thesecond instance.
The two most commonly usedtypes of electrolytic capacitors arethe tubular axial lead and thesingle -end printed circuit -typeshown in Fig. 1 and most commontwist prong "can" (Fig. 2), with oneor more sections with a commoncathode.
Electrolytic Capacitor Tolerances
Because of the electro-chemicalprocesses employed during themanufacturing of electrolyticcapacitors-along with the varia-tion in the etching process-it isdifficult to produce an electrolyticcapacitor close to its intendedcapacitance. This is generally nota problem when replacing acapacitor, because most circuitswill tolerate at least a fifty percentexcess capacitance and in manycases several hundred percent.
A typical electrolytic having atolerance of - 10 percent to + 50percent means that a 100 mfdcapacitor will have an actualcapacitance value of between 90
12 / ELECTRONIC TECHNICIAN/DEALER. JULY 1975
Fig. 2-The most common aluminum -casedelectrolytic twist prong "can" capacitor with oneor more sections containing a common cathode.
and 150 mfd. To find its exactcapacitance it would have to bemeasured.
Suppose a circuit is designed for60 mfd capacitor, we could replaceit with a 100 mfd to 120 mfd with-out any problems. The thing toremember is that it makes verylittle difference in a filter circuit touse a larger value, but never sub-stitute a capacitor having a lowerrated capacitance than the origi-nal value.
The maximum practical voltagelimit for electrolytics is 450 volts.By employing special processingmethods and careful selection ofmaterial, capacitors have beenproduced with a maximum volt-age rating of 525 volts. Themaximum operating temperaturemust be reduced from 85 degrees C(185 degrees F) to 65 degrees C(149 degrees F) for capacitorsrated at higher voltages. Acapacitor rated above 450 volts at150 degrees F can be operated at185 degrees F when used at 450volts or less.
As the voltage rating of an elec-trolytic increases, the capacitancetolerance becomes less. If a
Fig. 3-The popular disc -type ceramiccapacitor.
Fig. 4-Tubular axial lead ceramic capacitors
capacitor is rated at 1 to 50 voltsDCW at a tolerance of -10 percentto + 250 percent, above 350 voltsDCW, the tolerances would be re-duced to - 10 percent to + 50 per-cent.
When replacing an electrolyticcapacitor, always remember to useone with a capacitance rating of atleast as high as the original onereplaced, and a voltage rating atleast as high.
Electrolytic Capacitor Substitution
Electrolytic capacitors storelarge amounts of energy for theirsize and to replace them with apaper -type capacitor of equalvalue would be difficult with theavailable space. Also, they mayhave some electrical characteris-tics which may cause circuit mal-functions if replaced with thepaper -type.
Paper types cannot be substi-tuted with an electrolytic even ifthey are of equal value. The papertypes were chosen because of theirbetter voltage characteristics, orpolarity -reversal characteristics.The polarity of an electrolyticcapacitor is extremely important
and electrolytics do not providethe close tolerance needed in somecircuits.
Increasing The Capacitance andVoltage of A Capacitor
Often we find a circuit requiringa specific amount of capacitance,but only smaller value capacitorsare available. Suppose you need a60 mfd, 300 volt DCW capacitor,then simply place two 30 mfd, 300volt DCW capacitors in parallel.In some rare cases, we may changethe RC time constant enough tocause problems or the two paral-leled capacitors are too large forthe available space in the chassis,then the exact replacement is re-quired. When connecting twocapacitors in parallel, we increasethe capacitance, but the voltagerating remains the same. Unlikecapacitance, voltages in parallelare not additive.
If we find a circuit requiring ahigher working voltage, we canplace two capacitors in series. Two80 mfd, 150 volts DCW connectedin series will be equal to a single40 mfd, 300 volt DCW. The RCtime constant may change enoughin some rare cases, because the re-sistance is lower in the parallelcircuit and higher in the series cir-cuit than in an equivalent singlecapacitor.
Substituting Non -PolarizedCapacitors
In the event that a non -polarized twist -prong capacitor isrequired, place both positive leadsof two tubular electrolyticcapacitors through the respectivesolder lugs and connect the nega-tive leads together, but do notground them. You should employcapacitors with higher voltageratings and twice the capacity ofthe original. If two 100 mfd, 450volt DC capacitors are connectedback-to-back, we will now have a50 mfd, 300 volt AC non -polarizedcapacitor. This same arrangementcan be usea to replace tubularnon -polarized capacitors.
Electrolytic Capacitor Myths Dispelled
Listed are some of the commonmyths expressed by many elec-tronic technicians concerning thesubstitution of electrolyte capaci-
JULY 1975, ELECTRONIC TECHNICIAN/DEALER / 13
tors in different electronic circuits: Using a higher value capacitor
in the input filter circuit of thepower supply will increase the out-put voltage. Actually, the purposeof the filter is to smooth the ACripple. Increasing the input filtercapacity will not increase thevoltage higher than the peak ACvoltage.
If the original filter has losscapacity, a new filter capacitorwill increase the voltage, but onlyto the proper specified voltage.
Substitution of an electrolyticwith more capacitance will in-crease leakage. An old capacitorwill normally have more leakagethan a new capacitor with a highercapacity rating. With the excep-tion of some coupling circuits, thisis a minor factor.
Substitution of electrolyticcapacitors of higher capacitance insome coupling circuits will causethem to malfunction. This could betrue if the inductance of thecapacitor has increased because ofthe larger size and more layers ofelectrolyte. The latest manufac-turing process, employing hardaluminum foils, now makes it pos-sible to reduce its size for the samevalue to such a fraction of the orig-inal one that this is no longer animportant factor.
Electrolytic capacitors will de-form at lower voltages or whenstored on the shelf for a period oftime. The capacitors producedabout 10 or 15 years ago weremanufactured with those charac-teristics, but the new capacitorsare stable and will function atlower working voltages withoutdeforming and changing capacity.
The self -life of the newaluminum -cased capacitors areextremely long, as compared tothe ones manufactured manyyears ago. The stabilities of theelectrolyte and the purity of thealuminum used prevent them de-forming to lower voltage ratingswhen either idle or operating atlower voltages than the onesspecified on the original capacitor.
ELECTROSTATIC CAPACITORS
Electrostatic capacitors arevery different when we comparethem to electrolytic capacitors-not only in the way they are man-
ufactured, but in their circuit ap-plications. They are produced withclose tolerances generally around+ 10 percent, unless noted orspecified.
The most common dielectricemployed in the manufacturing ofelectrostatic capacitors include:impregnated paper, ceramic,mica, film and air.
Ceramic Capacitors
Ceramic is probably the mostversatile dielectric offeringunique characteristics. The mate-rial can be used proportionately indifferent methods to provide thevarious types of ceramiccapacitors.
Their physical styles are almostas varied as their electricalcharacteristics, which include thepopular disc, Fig. 3, tubular axiallead, Fig. 4, and extend into themore sophisticated, Fig. 5, trim-mer (variable and feedthroughtypes). The disc and tubular stylesare the most common in theirsimplist forms. They consist of acircular disc or a hollow tube ofceramic dielectric with metal elec-trodes applied to their opposingfaces. Wire terminals are con-nected to the electrodes and thebody of the capacitor is coveredwith insulating material. Becausethey employ ceramic as a dielec-tric and their comparativesimplicity, they are generally verylow in cost, but they are very reli-able.
There are four types of ceramiccapacitors, general-purpose, tem-perature -compensating, tempera-ture -stable, and frequency stable.
FILTERING
COUPLING
BYPASS
ENERGY
STORAGE
TUNING
TEMP.COMP.
General -Purpose: The construc-tion of this capacitor is common toother disc ceramics. It can beemployed as substitutes for mica,paper, or polyester types in filter,bypass, or coupling capacitors innon -critical circuits. A generalpurpose miniature monolithiccapacitor with epoxy coating isshown in Fig. 6.
Temperature -Compensating:These capacitors have a widerange of available temperature-co-efficients. The P types capaci-tors have a positive temperaturechange while the N type have anegative change. The NPO typehas practically no capacitancechange from - 25 degrees C to 85degrees C.
The prefix letter P on a capaci-tor means that above + 25 degreesC, the capacitance will increasewith the temperature (or a posi-tive co -efficient); N means thecapacitance will decrease (nega-tive co -efficient); and the lettersNPO designates no change exceptwith the NPO type which does nothave a number.
If we find a designation of P100,
Fig. 5-The trimmer (variable) and the feedthrougt ceramic capacitors are the more sophisticated types.
ilrAIR CERAMIC MICA PAPER
PLASTICFILM
ALUM.ELECT
TANTELECT
Vi/
VPRIMARY APPLICATIONS OF CAPACITORS IN HOME ENTERTAINMENT PRODUCT
14 / ELECTRONIC TECHNICIAN/DEALER, JULY 1975
it signifies that for every degreecentigrade of temperature in-crease (between + 25 degrees Cand +85 degrees C), the capaci-tance will increase 100 parts permillion. A capacitor with an N750rating provides a decrease of 750parts per million per degree in-crease, and an N1400 will providealmost twice the amount.
Temperature -Stable: The tem-perature stable capacitor is quitesimilar to the NPO type with somerefinements. Its temperaturerange has been increased so thatfrom - 60 degrees C to + 100 de-grees C, the capacitance changesonly + 7.5 percent from the statedvalue at + 25 degrees C.
Frequently -Stable: The capaci-tors are constructed so that theywill maintain a relatively con-stant resonant frequency overtheir operating temperaturerange.
The tolerance of ceramiccapacitors will be rated in guaran-teed minimum value (GMV) or inpercent. The GMV rating is themanufacturer's guarantee thatthe capacitor will not have less
capacitance than stated at 25 de-grees C.
Mica Capacitors
A few dipped -mica capacitorsare used in consumer electronicproducts and are very reliable.They are identified by ink stamp-ing, manufacturer's name or sym-bol, minimum capacitance inpicofarads, tolerance in percentand the DCW. They can be ob-tained with one percent toleranceor better.
The mica capacitor has a highdegree of stability over a largerange of operating temperaturesand quite often employed whereradio frequencies are encoun-tered.
Many ceramic capacitors can bedirectly replaced with dipped -mica types providing better per-formance and dependability. Thisreplacement does not apply totemperature compensating appli-cations.
Plastic -Film Capacitors
Polyester -Film: Those capaci-tors (Fig. 7), are used quite exten-
Fig. 8-General purpose ceramic capacitors with an epoxy coating for environment protection.
Fig. 7-Plastic-Film capacitor. Fig. 8-Polystyrene film capacitor.
sively in home entertainmentproducts and solid-state transis-torized circuitry has expandedtheir use.
The advantages of these capaci-tors are: they are very dense; theycan be produced into very thinsheets which are fairly stable asfar as their physical size; and theyhave a high dielectric strengthalong with good insulation resis-tance.
The construction of the polyes-ter -film capacitor is similar to thatof a paper type. The impregnatingoils are not used because thedielectric qualities are dependenton the film itself.
The most popular types are thedipped, molded, and wrap -and -fillstyles which are all extended -foilconstruction with less inductance.
Polystyrene -Film Capacitors:These capacitors, shown in Fig. 8,offer good stability in a smallpackage. Its insulation resistanceis very high in comparison to all ofthe other commonly used capaci-tors. Aging has practically no ef-fect on its capacitance value andthey have a slightly negativetemperature -coefficient.
The disadvantage of thiscapacitor is that its upper temper-ature range is only approximately+ 85 degrees C.
Rules For ReplacingElectrostatic Capacitors
Dipped paper Mylar capaci-tors can generally be used to re-place film, paper and combinationpaper -film capacitors.
Dipped epoxy capacitors willreplace wrapped, molded or pottedconstruction types.
Mica capacitors can be substi-tuted for ceramic capacitors wheretemperature compensation is notcritical.
Capacitors with higher volt-age ratings can be used, except infrequency sensitive circuits.
DC rated capacitors should bedecreased when used for AC appli-cations.
The capacitor value is de-creased if its operating tempera-ture is exceeded.
Power capacitors are usuallyrated at AC voltage and in mostcases can not be replaced with DCcapacitors.
JULY 1975 ELECTRONIC TECHNICIAN/DEALER / 15
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Partial List of ContentsAdmiral-Chassis 11A9N; G11; G13; H10;
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"Exotic" Semiconductors-Theory & Testing
By Bernard B. Daien, ETD Contributing Editor
How UJTs, PUTs, Diacs and Triacs functionand how to test them and SCRs
The unijunction transistor(UJT) is an interesting devicewhich can be used in silicon -controlled rectifier (SCR) firingcircuits, timers, waveformgenerators, and a number of otherapplications. It has been aroundfor a long time, but, until lately, itcosts a bit more than most enter-tainment equipment manufactur-ers cared to spend. As a result, itsuse generally was confined to in-dustrial controls and military ap-plications.
Recently, however, the PUT(programable uninjunction tran-sistor) was developed. It offers thesame level of performance as aconventional unijunction transis-tor, but at a much lower cost. ThePUT is almost identical in appli-cation and function, but is quitedifferent in construction.
Fig. 1 illustrates the basic in-ternal construction of a UJT. Asingle crystal bar of N type mate-rial has an electrical connectionmade to each end. Somewhere be-tween the ends a "tap" is made inthe form of an electrical connec-tion to some P type material. This
forms a PN junction, the same as adiode. Because the UJT only has asingle junction, it is called a uni-junction transistor. The bottom ofthe bar is labeled Base 1, the topBase 2, and the tap is the Emitter.
Fig. 2 shows the schematic sym-bol for a UJT with the terminalsidentified.
Fig. 3 illustrates how the UJTfunctions. When a source of volt-age is impressed across the bar,current flows through the bar as itwould through any resistance. Be-cause the emitter is tapped intothe bar in a manner similar to thetap point on a tapped resistor, wecan show this schematically bymeans of imagined resistors R2and RI . And because the emitter istapped into the bar via some Ptype material which forms a PNjunction, the resultant junction isrepresented in Fig. 3 by diode D1.
If we assume that the tap wasmade at the center of the bar, then+ 5 volts would appear at the tap,as shown. If we now apply lessthan + 5 volts to the emitter con-nection, diode D1 will be reversebiased, and no current will flow
BASE 2
EMITTER
P TYPEMATERIAL
SINGLE CRYSTALBAR OF N TYPE
MATERIAL
BASE 1
Fig. 1-Physical design of a UJT.
BASE 2
EMITTER jBASE 1
Fig. 2-Schematic symbol of a UJT.
into the emitter. If more than +5volts is applied to the emitter,diode Dl becomes forward biased,and emitter current flows fromBase 1 through Dl to the emitterconnection. Once current flowsfrom base to emitter, the emitterinput resistance decreases and,consequently, the voltage acrossthe emitter -base junction de-creases because of the loweredinput resistance. Despite this de-crease in voltage, the emitter cur-rent remains heavy because thejunction is forward biased. The in-jection of emitter current releasesstill more current as a result ofsemiconductor action.
The combination of a decreasingvoltage and an increasing currentis indicative of what is called anegative resistance, which is theprincipal operating characteristicof the UJT. The emitter of the UJTexhibits negative resistance,which can be used for many appli-cations, as explained later.
Fig. 4 shows the negative resis-tance of the UJT in graphic form.When the emitter is below the"peak point," very little emitter
20 / ELECTRONIC TECHNICIAN/DEALER, JULY 1975
BASE 2
EMITTER +5V
041-D
foy
jRi
BASE 1
1o11
Fig. 3-Functional diagram which illustrates theoperating theory of a UJT.
CI PEAK POINT, (VP)1-_10
VALLEY, (Vv)cc
H21111
0 EMITTERCURRENT
Fig. 4-Graph which illustrates the negative resistance characteristic of the emitter of a UJT.
current flows because the emitteris reverse biased. When the "peakpoint" is passed, the emitter be-comes forward biased, and simul-taneously the emitter current in-creases while the emitter voltagefalls to the "valley" level.
Now, let's look at an illustrativeUJT circuit and its typicalwaveforms. The circuit in Fig. 5 isa UJT relaxation oscillator. Whenvoltage is first applied to the cir-cuit, capacitor C charges towardsthe emitter peak point (VP). WhenVP is reached the emitter becomesforward biased, discharging thecapacitor to the valley voltage (Vv)level. As the cycle repeats itself, asawtooth waveform is created atthe emitter (providing that charg-ing resistor R1 is reasonablylarge). If the value of R1 shoulddecrease to under 10,000 or soohms, the emitter might stay
+ 20V
cn
0
VP
IVV
71/10 EMITTER
cT
Fig. 5-UJT-equipped re'axation oscillatur.
0
-
BASE 2
cn
0
BASE 1
latched on. This is an importantpoint to remember, because thefrequency of oscillation is deter-mined by the values of R1 and Cand a constant determined by thetype of UJT. An attempt to in-crease the frequency of oscillationby reducing R1 to a very smallvalue will stop oscillations.
The waveform at Base 1 in Fig. 5is a positive -going, sharply peakedpulse. The waveform at Base 2 is anegative -going pulse. From this itcan be seen that the UJT can pro-vide several different types ofwaveforms with few externalcomponents. Typically, it is oper-ated as a pulse and nonlinearwaveform generator, and not as alinear amplifier like a bipolartransistor.
The emitter pulse waveform inFig. 5 is frequently used (viacapacitor or transformer coupling)for SCR firing purposes because ithas the fast rise time and suffi-cient energy (capacitor discharge)required to insure efficient SCRtriggering.
TESTING UJTS
The circuit in Fig. 5 can be usedas a simple UJT good/bad tester.Use a .05-mfd capacitor, a33,000 -ohm resistor (for R1), and47 -ohm resistors for the base re-sistors. A 9 -volt transistor batterywill suffice for a power source. Asmall 16 -ohm speaker placed
across the Base 1 resistor will au-dibly indicate oscillation if theUJT is operating normally.
In -circuit testing of UJTs can bedifficult, because the narrowpulses used in many circuits arenot readily visible on most servicetype scopes, and DC tests per-formed with multimeters do notindicate the presence of suchpulses at all. Further, since theUJT only has one junction, as pre-viously discussed, attempts toevaluate its condition by themethods used to check a bipolartransistor (forward and reverseresistances of both junctions) arenot applicable. It is recommendedthat the out -of -circuit oscillationtest be used.
THE NEED FOR PUTS
Before we can go futher, a newterm, Intrinsic Standoff Ratio,must be defined. Despite the for-midable name, it is quite simple. Ifyou look again at Fig. 3, it is obvi-ous that if the emitter "tap point"is placed higher or lower on thebar, the peak firing point will bechanged accordingly. The higherthe tap on the bar, the more volt-age it takes before the peak pointis reached.
Since we are dealing with avoltage divider, the peak point isalways a fraction of the totalapplied voltage, and the fraction isdetermined by tap location. The
JULY 1975, ELECTRONIC TECHNICIAN/DEALER / 21
symbol for this fraction is "n" theGreek letter similar to a lowercase letter "n." This is the IntrinsicStandoff Ratio, and is used as fol-lows: Assume we have applied 20volts to a UJT with a standoffratioof 0.5. The emitter peak point willfire at 0.5 times the applied volt-age, or 0.5 times 20 volts = 10volts VP. So you see that the stand-off ratio merely describes wherethe tap is on the bar, and in thiscase it was at the 50 -percent point.The standoff ratios of most UJTsrun between 0.5 and 0.9, princi-pally because of factors related tothe design and fabrication of thedevice.
As you can see, the standoffratio is fixed. The actual standoffratio usually is slightly differentthan the published value becauseof the forward junction voltagedrop. (The emitter is a junctionsimilar to a diode.) If you shouldneed a UJT with a different stand-off ratio, you have to buy one, andas with all components, there aretolerances. If you need a "tight"tolerance, you are in for a job ofselecting one out of many by test-ing each one. To overcome thisproblem, a new device has beendeveloped. It is called a Program-mable Unijunction Transistor(PUT).
PUTS AND SIMILAR DEVICES
To better understand the PUT,we will first examine its basicstructure, which also is common toSCRs, Triacs, Diacs, and many
other "snap action" devices. Fig. 6illustrates the derivation andbasic structure of such devices.
Fig. 6A shows a PNP and anNPN transistor connected to forma "latching" circuit. When voltageis applied to the anode and cathodeterminals, no current flows be-cause both transistors are in the"off" state. If, however, one of thetransistors can be made to turn on,it will, in turn, forward bias theother transistor. (The collector ofeach transistor is tied to the baseof the other transistor.)
Once turned on, the circuit inFig. 6A will stay latched on be-cause each transistor continues tosupply base drive to the other. Thecircuit can be turned on intention-ally three ways, and inadvertentlyone other way. If the terminallabeled "anode gate" is suppliedwith even a momentary pulse thatis negative with regard to theanode, the PNP transistor willturn on, initiating latchup. If the"cathode gate" is made evenmomentarily positive with respectto the cathode, the NPN transistorwill turn on, with the same result.And, if the voltage between anodeand cathode is increased beyondthe voltage rating of the devices,"break over" occurs, causing turnon and latchup.
It is possible to cause undesiredturn -on of the circuit in Fig. 6A byapplying voltage at such a rapidrate that the steep wavefrontreaches the gate via the junctioncapacitances. This also can hap-
CATHODEGATE 0-
A+ ANODE"
ANODEGATE
"CATHODE'
B
ANODE
CATHODEGATE
CATHODE
ANODEGATE
C
ANODE
ANODEGATE
CATHODEGATE
CATHODE
Fig. 6-Illustration which reveals the basic structure (A) of a lour -layer semiconductor device and the"evolution" of the basic structure into a device with two separated but interconnected transistors (B)and. finally. into a practical four -layer device (C) which, with minor variations in construction. isuseful as an SCR, a PUT and a Diac.
pen due to transients. (Remember,it takes only a short durationpulse to cause turn -on.) To preventthis unwanted turn -on, small ex-ternal capacitors, resistors or in-ductances often are used as low-pass filter elements.
Fig. 6B shows the PNP andNPN internal transistor struc-tures, along with the wiring inter-connections and terminals. Noticethat the N segments are tied to-gether, as are the P segments.
In Fig. 6C the two separatestructures have been consolidatedinto one, eliminating the inter-connections. This is the basic fourlayer semiconductor device whichcan be used in many ways. Slightdifferences in fabrication are usedto optimize performance for par-ticular uses. For example: An SCR (silicon controlled recti-fier) omits the anode gate lead,and thus is fired only by a pulsethat is positive with respect to thecathode. The PUT omits the cathode gatelead, and is fired by a voltage thatis negative with respect to theanode. The DAC omits both gate leads,and is fired by break -over causedby excessive applied voltage. (Thisdevice also is called a bilateralswitch, and in some versions ismade of only 3 layers.) The Triac is a somewhat morecomplex device. It can be consi-dered to be two SCRs in parallelbut with reverse connections (eachanode connected to the othercathode). This "composite SCR"can be turned on by voltage ofeither polarity, whereas an SCRcan be turned on only when theanode is positive. The one gate ofthe Traic turns on the device whenit is driven by a voltage of thesame polarity as the anode termi-nal. For example, when the anodevoltage is positive, the Traic turnson if a positive voltage also isapplied to the gate. When theanode is negative, application of anegative voltage to the gate willturn on the device.
TESTING SCRS AND TRIACS
All variations of four -layerdiodes are non linear devices,which means that they generatepulses or other waveforms whose
22 ELECTRONIC TECHNICIAN DEALER, JULY 1975
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shapes are unrelated to the inputvoltage waveform. Generally,SCRs and Triacs are used aspower -switching devices at fre-quencies up to 100 KHz, whileUJTs, Diacs and four -layer diodesare used in the same frequencyrange to drive power switches andperform other functions (exceptlinear amplification).
Because four -layer devices donot amplify in a conventionallinear manner, they are difficultto test with the usual methodsused for linear devices. In mostcases, such tests are meaningless.There are, however, some simplein -circuit tests that can be per-formed on SCRs and Traics(power -switching devices) withcommon TV test equipment. Thekey to such testing lies in the factthat four -layer devices "latch up"(conduct) when certain conditionsexist, and stay latched until thecurrent through them drops tozero for a period of time sufficientto enable the device to turn off.The current can be made to drop tozero by placing a reverse bias onthe device, by interrupting (open-ing) the circuit with another de-vice or component. What we arelooking for is one of the followingconditions: A) A shorted device,B) an open device, C) a device thatdoes not respond to the normal"turn on" signal, or D) a devicethat does not turn off with a nor-mal "turn off" condition.
Testing The SCR
Like an ordinary rectifier, theSCR never conducts when it is re-verse biased. Unlike a rectifier,the SCR conducts in its forwarddirection only if its gate is drivenpositive with respect to its cathodefor a certain minimum period oftime (turn -on time interval).
The following checklist shouldmake SCR troubleshooting easierfor you:
1) Does the SCR stay on all thetime?
a) If yes, does the voltageacross the SCR go to zero (or re-verse bias) for several mic-roseconds for a "fast switching"type SCR, or for ten times thatlong for a standard -speed SCR?
b) If yes, you should also de-
termine if the gate drive is everabsent.
c) If gate drive is absent, andvoltage across the SCR goes to zerofor the appropriate time, the de-vice must turn off if it is good.
2) Does the SCR stay off all thetime?
a) If yes, is proper gate drivesupplied during the interval theanode is forward biased? (Gatemust be positive with respect tocathode for the appropriate inter-val of time, to insure turn -on).
b) If the anode is positive andthe gate is driven with a propersignal, the SCR must turn on ifgood.
The preceding checklist as-sumes that you have made theusual check of anode supply volt-age before testing the device. Thegate drive can be checked only bydisconnecting the lead to the gateand examining the waveformamplitude and duration on ascope. The gate drive waveformcannot be analyzed with the gatein the circuit, since the gate/cathode forms a diode, whichclamps the waveform at theamplitude level of the diode for-ward drop. Once the SCR goes intoheavy conduction, the internalvoltage drop "masks" the applieddrive.
The preceding list also tells youwhat circuit defects to look for andwhat voltages will be present orabsent for each. Note, however,that you must use a little commonsense too. For example, the SCRshould remain on only if the gatedrive is present during the inter-val the anode is forward biased,(Gate drive during anode reversebias is ineffective, as SCRs onlyconduct when forward bias isapplied to the anode.) An SCRwhich conducts on the reversebiased half of an AC cycle isshorted.
Testing The Triac
Triacs can be triggered on whenthe anode is negative or positive,although the gate sensitivity var-ies from state to state. This tendsto make testing a little confusing.Things become a little clearer ifyou consider the Triac as a solid-state relay, replacing a magneticsingle -pole, single -throw relay. It
CURRENT
Vi Vs
.der"
.0- VOLTS0
VOLTS+ -
Vs V
Fig. 7-- -Voltage -vs current graph fnr a typicalDiac.
works on AC or DC of either polar-ity, just the way the magnetic (orreed) relay works, with one excep-tion: Magnetic relays stay acti-vated as long as the coil is ener-gized, and open only when the coilis deenergized, but the Triac stayslatched up even after the gatedrive is removed. Just as with anSCR, the voltage across the Triacmust go to zero long enough for theTriac to unlatch. Unlike an SCR,reverse bias won't turn off a Triacunder many circumstances, be-cause the Triac works with volt-ages of either polarity.
As with SCRs, when trouble-shooting Triacs you will be look-ing for a shorted or open device, orone which does not respond to thegate signals. If the Triac stays onall the time, disconnect the gatelead. If the Triac still stays on, it isdefective. If not, the gate drivesource is at fault.
If the Triac stays off all the time,disconnect the gate lead and checkfor the gate drive, which should beseveral volts for more than 25 mi-croseconds. If there is gate drive,the Triac is probably defective. Ifthere is no gate drive, the problemis in the gate drive or eariler sens-ing circuits.
Again, remember to check theanode supply voltage. Semicon-ductors, like vacuum tubes, do notfunction properly without the cor-rect voltage applied.
THE DIAC
Up to this time we have merelymentioned that these diodes areused frequently to fire SCRs andTraics, but there was no discus-sion as to why they are so popularin this application. Fig. 7 helps toillustrate why. It is a volts -versus -current curve for a typicalDiac.
Note that as the voltage acrossthe Diac is made more positive,
24 I ELECTRONIC TECHNICIAN/DEALER, JULY 1975
DIAC.
ACINPUT LOAD
Fig. 8-A representative Diac-equipped circuifor triggering an SCR or Triac.
very little current flows until theswitching voltage level, Vs, isreached. Then the device "snaps,"the current increases very rapidly(in microseconds), and the voltageacross the device falls to a lowvalue, termed the holding value,VH.
If the Diac is used in a circuitlike that in Fig. 8 (which alsoshows the symbol for a Diac), theoutput will consist of one pulse foreach half cycle of AC input. Thepulse is negative for a negativehalf cycle, and positive on the posi-tive half cycle. Operation is as fol-lows: The capacitor charges. Whenthe voltage across the capacitorreaches the Diac's switching volt-age, the Diac suddenly conducts,and the voltage drop across it de-creases. The capacitor then dis-charges into the load through thelow forward resistance of the Diac.Since the capacitor's dischargecurrent is limited primarily by theload resistance, a relatively largecurrent can flow through theDiac. This is very desirable forSCR and Triac firing because theirgates should be driven by a pulsewith fast rise time and relativelyhigh current and high voltage,thus insuring fast turn -on. Aslowly rising pulse would result inslow turn -on, causing high SCRdissipation and other undesirableeffects.
As illustrated in Fig. 7, the Diacworks equally well with positiveor negative voltage applied; con-sequently, it works in the samemanner on both the positive andnegative half cycles, which isnecessary when driving Triacs.(Remember, Triacs operate onboth halves of the AC input cycle.)
SCR, TRIAC AND DIAC SYMBOLS
Fig. 9 shows the schematic sym-bols for this family of devices,along with element labels.
ASCR
ANODE
BTRIAC
TERMINAL 2
GATE 7T GATE
CATHODE TERMINAL 1
CDIAC
A
Fig. 9-Schematic Symbols for an SCR (A).a Triac (B), and a Diac (C).
Fig. 9A is the SCR symbol withthe anode, cathode and gateclearly labeled.
Fig. 9B is a Triac, the gate ofwhich is easily identifiable, butthe other two terminals aremerely titled "Terminal 1" and"Terminal 2," since either can beconsidered to be an anode, or acathode, depending upon the di-rection of conduction.
Fig. 9C, a Diac, normally has noterminal labels at all, since it is asymmetrical device which func-tions equally well in either direc-tion.
GATE AND OUTPUT MEASUREMENTS
When troubleshooting semi-conductor switching devices, re-member that the triggering and/oroutput waveforms of such devicesmight be a half or a quarter cycleof a sine wave or might be a nar-row pulse, depending upon theparticular device and its applica-tion, and that conventionalservice -type meters cannot be re-lied upon to give meaningful indi-cations of such pulse -typewaveforms. A narrow pulse mightnot produce any type of meter in-dication at all, and low -duty -cyclewaveforms of, say, 100 voltsamplitude might produce lowreadings. Only peak -reading me-ters and oscilloscopes are accuratedevices for these nonlinearwaveforms. The peak meters atleast indicate what the peak valueof the wave is. A scope, the bestchoice of all, shows the wave -shape, duration and amplitude,providing it is a wide -band scopewith a stable triggering systemcapable of "catching" fast, narrowpulses. The newer service scopeswith a useful 10MHz bandwidththat is flat to 5 MHz are adequate.But if your scope is "3dB down at4.5 MHz," it actually reads 7 voltson a 10 -volt peak signal at 4.5
MHz if you calibrate it at a lowfrequency. A 30 percent error isthree times greater than accepta-ble, even for the "roughest" sort ofservice work. If your scope is rated"plus or minus 1 db" at 4.5 MHz, itis satisfactory for all but the mostcritical type of measurements youwill encounter in the servicing ofsemiconductor switching devices.
SELECTING REPLACEMENTS
All devices with a 1N-, or2N-number are registered andsupposed to conform to a uniformstandard, so they should be inter-changeable. Several manufactur-ers are now providing approval forsubstitutes provided by semicon-ductor firms, (among these areZenith), and that's a big help."House number" parts often canbe replaced by parts recommendedin service literature for theequipment prepared by indepen-dent major publishers. A good ruleis: "When in doubt, get an originalreplacement part." SCRs, Diacs,etc., are sorted out on a voltage/current/turn-on and turn-off timebasis. The average service shopsimply does not have the requiredtime and test equipment to gradeout devices for substition pur-poses.
During 1974-75, there has beena noticeable increase in the atten-tion semiconductor manufactur-ers have given to the replacementparts market. This is probably be-cause their OEM business has de-clined. In any event, the replace-ment and substitution manualsnow offer more items, are betterorganized, and are more accuratethan in the past, and, con-sequently, they are more useful.In general, the parts offered as"substitutes" are capable of with-standing more voltage and cur-rent than the original parts, andin the case of older types of de-vices, the newer versions offeredare superior in most other respectstoo. Despite this, if the part has astandard 1N-, 2N- or 3N-number, or some other commonlyencountered number, you usuallycan save real money by buyingit under that number instead ofthe "replacement part number"offered in crossreference litera-ture.
JULY 1975. ELECTRONIC TECHNICIAN DEALER 25
New capacityto 10,725 lbs. GVWNow you can consider compact Ford Par-cel Vans for jobs previously too big or tooheavy for this type of truck. New 14 -ft.body is 8 ft. wide, offers 40% more cubethan Ford's biggest '74 model. GVIV's to10,725 lbs. boost payloads, too. For easyloading, hinged rear doors are almostbody wide. Doors swing open all the wayagainst body sides...have slam -shutlatches, provision for locking. Options in-clude roll -up doors, cab partitions with orwithout walk-thru, roof vents, rub rails.
12 -ft. body has 138 in. wheelbaseIt's 7 ft. wide on E-250, 8 ft on E-350.
14 -ft. body has 158 in wheelbase.Body is 8 ft. wide, has 6'2" headroom..,
New driver roomand comfortFord gives the driver what he needs toget more done with less effort. Big, widecab doors make getting in and out easy.Because the engine is forward out of theway, driver can easily step back into theload area-or across to the curbside cabdoor. Both driver and helper have goodlegroom and footroom. Thick, insulatedengine cover has handy pockets on top.
New durabilityengineeringSeparate body with frame, the onlyAmerican van with this construction, pro-vides a strong foundation for the entirevehicle. Frame rails are designed to helpcushion impact from the front. To resistcorrosion, key components are galvanizedand the entire cab is primed by deep -dipElectrocoat. These vans are built to keeptheir value. Cruise-O-Matic, power frontdisc brakes, 300 Six are standard.
Energy -absorbing frame rails help cushion frimpact Frame is the first in any American war,
Standard and auxiliary fuel tanks are locatedbetween the frame rails, total up to 42.6 gallons
26 / ELECTRONIC TECHNICIAN/DEALER, JULY 1975
For '75, Ford redesigns theParcel Delivery Van.
New high -capacity Econolinesoffer bodies to 14 ft. long, over 40% more cube,
new efficiency for delivery operations.
Engines to match the job; choiceof 300 Six, 351 -cu. in. V-8, 460 -cu. in.V-8. All truck strengthened.
Forward engine locationpermits 17 outsideservice checks.
Improved Twin -I -Beam suspensionprovides front-end toughness andstable ride
Cruise-O-Matic Drive, powerfront disc brakes are standard;power steering optional.
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Engine and wheelhousingsmoved forward for more driverand passenger room. comfort
Offered with single rear (E-250)or dual rear wheels (E-350).
Econoline Vans: Four serieswith GVW's to 10,000 lbs.Virtually all of the advantages of Ford Parcel Vans, like strongbody -frame construction, apply to regular '75 Ford EconolineVans. You also get a greater choice of models and options tomatch your needs, new highs in weight capacity, 12 in. longercenter load length than last year, new 54 -in. wide rear doors,sliding or hinged side cargo doors. See your Ford Dealer now.
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...for more details circle 133 on Reader Service CardJULY 1975. ELETRONIC TECHNICIAN/DEALER 27
Powers, Logs & dBs--A Brief Review By Jack Hobbs and J.W. Phipps
If you are like most of us, youprobably were "exposed" to powersof ten, logarithms and decibelcomputations a few years ago dur-ing the "math portion" of a formalelectronics course. And, unlessyou are one of the rare electronictechnicians who uses these areasof math on a daily or even weeklybasis, you, like most of us, proba-bly have gotten a little rusty. If so,the following brief review of thefundamentals of powers of ten,logarithms and decibels shouldhelp brush away some of themathematical cobwebs, so thatyou'll feel a little more comforta-ble when the occasional need formathematical computation arisesin your "practical" workadayworld of servicing electronics.
POWERS OF TEN
The principal reason for usingpowers of ten is to simplify themultiplication and division of thelarge whole numbers and/or largedecimal fractions which electronicmathematical computations in-evitably involve.
TABLE 1POWERS OF TEN
AND EQUIVALENTS
Power Equivalent Value TermAbbre-viation
10'2 1.000.000.000.000 Tera - T
10" 100.000,000,00010'0 10.000.000.000108 1.000.000.000 Giga-108 100.000.00010' 10.000.000108 1,000.000 Mega - M108 100.000104 10.000103 1.000 Kilo - K102 10010' 10
100 1
0.1 deci-10-810-8
0.01
0.001-centimilli-
m
10-8 0.000110-8 0.0000110-8 0.000001 micro-10-7 0.000000110-8 0.0000000110-8 0.000000001 nano-10-18 0.000000000110-11 0.0000000000110-12 0.000000000001 pico- p
Expression of a number in pow-ers of ten is merely a way of stat-ing how many times a smallernumber (and subsequent productsderived from it) have to be multi-plied by ten to equal it. For exam-ple, to equal 100, the number 1 hasto be multiplied twice by 10, or 1 x10 = 10 x 10 = 100. This samemathematical expression can beabbreviated to read: 100 = 1 x 102.
Similarly, to equal 1000, thenumber 1 must be multiplied by10 three times, or 1 x 10= 10x 10= 100 x 10 = 1000. And, likewise,this mathematical expression canbe abbreviated to read: 1000 = 1 x103.
To express any whole number asa smaller whole number and/ordecimal fraction, move the deci-mal point to the left as manyplaces (digits) as you deem neces-sary for convenient computationand then use the number of placesas the power of ten exponent. (Inthe expression 1000 = 1 x 103, thesmall 3 is the exponent, or power.)For example, to express thenumber 1361.5 as a smaller wholenumber, the decimal point ismoved three places to the left andthe "new" number is expressed as1.3615 x 103.
Decimal fractions, such as.4632, can be expressed as wholenumbers in the same manner ex-cept that the decimal point ismoved to the right and a negativesign is placed before the exponent.For example, .4632 can be ex-pressed as 4632 x 10-4.
Listed in Table 1 are the wholenumbers in multiples often from 1to 1 trillion and their equivalentvalues expressed as powers of ten.Also included are decimal frac-tions in multiples of ten from .1 to1 pico and their equivalent valuesexpressed in powers of ten.
As stated previously, the prin-cipal reason for using powers often is to make large whole num-bers and/or large decimal frac-tions easier to multiply and di-vide. Examples of these applica-tions of powers of ten are shown in
the computations in Table 2.
COMMON LOGARITHMS
The logarithm, like the power often, is a method of "re -phrasing"numerical quantities so that theycan be more easily multiplied anddivided. As with powers of ten,multiplication of logarithms is ac-complished by algebraic addition,and division is accomplished byalgebraic subtraction.
In the common system oflogarithms, the logarithm (ab-breviated "log") of a number is thepower, or exponent, to which thenumber 10 must be raised to equalthat number.
As you will recall from the pre-vious discussion of powers of ten,10 can be expressed as 100, 100 canbe expressed as 102, 1000 can beexpressed as 103, etc. Numbers be-tween even multiples of ten (forexample, those between 1 and 10,10 and 100, and 100 and 1000, etc.)are expressed as the same, or"original," group of digits (minusthe zeros which precede or followit) plus a power of ten exponent(such as 102) which tells how manytimes that number must be mul-tiplied by 10 to equal the "origi-nal" number. For example, 5600can be expressed in powers of tenas 56 x 102.
On the other hand, commonlogarithms convert an "original"numerical quantity into a com-pletely different, two-part numer-ical expression which tells howmany times 10 must be multipliedby itself to equal "the original"numerical quantity. In otherwords, the log of a number tellsyou to what power ten must beraised to equal that number.
The first segment of a log is awhole number called the charac-teristic. The characteristic of anumerical quantity equal to 1 orgreater is computed by countingthe number of digits to the left ofthe decimal point and then sub-tracting one. For example, thecharacteristic of 1560.8 is 3.
The characteristic of a numeri-cal quantity less than 1 is com-puted by counting the number ofdigits to the right of the decimalpoint and then adding a negativesign. For example, the charac-teristic of .0456 is -4.
The other segment of a
28 ELECTRONIC TECHNICIAN DEALER. JULY 1975
logarithm is a 4 -digit decimalfraction called the mantissa. Themantissa is obtained from a tableofcommon logarithms, a portion ofwhich is shown in Table 3. To findthe mantissa of a particular nu-merical quantity, locate in the "N"column of the log table the firsttwo -digits of the number. Thenproceed horizontally along thisline of numbers until you reachthe vertical column whose head-ing number corresponds to thethird digit of the number you areconverting to a log. The four -digitnumber in this column is the man-tissa. For example, the mantissa of1560.8 is found by searching downthe "N" column until you come to15, then proceed horizontally tothe vertical column with a head-ing of 6. The mantissa of 1560.8 is.1931. By combining the charac-teristic (3) and the mantissa(.1931) you arrive at the log of1560.8, which is 3.1931.
If the number you are convert-ing to a log has only one or twodigits, or if the third digit is a zero,always use the first, or "zero," ver-tical column. For example, to findthe mantissa of 2, 200 or 2000,proceed down the "N" column to 20and use the mantissa under the"N" vertical column, which is3010. The complete log of 2 is.3010, the complete log of 20 is1.3010, and the complete log of 200is 2.3010.
If the number you are convert-ing to a log has more than threedigits, you can find the fourth digitby referring to the 'proportionalparts" segment of the log table inTable 3. (Four -place logs are thehighest accuracy you will need formost electronic -related computa-tions, and three -place logs areusually adequate.) For example,to find the mantissa of 1543.6, find15 in the "N" column and thenmove horizontally to the "4" col-umn, which gives a "three -place"mantissa of .1875. Then proceedon the same horizontal line to the"3" column of the proportionalparts segment, which gives afourth -digit readout of .0008. Add-ing the .1875 and the .0008 pro-duces a mantissa of .1883, which isaccurate to four places. The com-plete log of 1543.6 is 3.1883.
The antilog of a log is merely the"original" number which was con-
verted to a log. An antilog is foundby first finding the log's mantissain the log table and then combin-ing the "N" column two -digitnumber and the single digit in theheading of the vertical column inwhich the mantissa appeared. Thedecimal point is then placed to theright a number of spaces equal tothe characteristic plus 1. (For logswith negative characteristics, thedecimal point is positioned to theleft a number of spaces equal to thecharacteristic.) For example, theantilog of log 3.3118 is 20 ("N" col-umn digits) and 5 (mantissa col-umn heading), producing 2050.
Examples of the applications ofcommon logarithms in electronicsare given in the following discus-sion of decibels.
DECIBELS
A ratio of 20 called the bel hasbeen used for years as the basis forcomputing and expressing manyelectronic measurements thatotherwise would be more difficultand less accurate. However, be-cause the bel, like the farad, forexample, is a large unit, the de-cibel (0.1 bel, abbreviated dB) isused for most practical applica-tions.
The dB is the logarithm of theratio of two powers, two voltagesor two currents. Or, we can saythat the dB is a unit of measure-ment of the ratio of two quantities.
The dB is used in measuring,computing and expressing powergain or loss, voltage gain or lossand current gain or loss. Specificapplications include checking fre-quency response variations inaudio amplifiers; measuring am-bient noise and other sound levels;and computing antenna gain overthat of a half -wave dipole or anisotropic.
One good reason for employingdB formulas, and thereforelogarithms, is to avoid multiply-ing and dividing complicated fig-ure groups. By using dBs, the pro-cess is frequently reduced to sim-ple algebraic addition and/or sub-traction. Logarithms minimizefiguring and reduce multiplica-tion and division to simple addi-tion and subtraction, respectively.
Why The Logarithmic Decibel
The human ear responds to dif-
ferent levels of sound in a non-linear manner. A given volume ofsound must be changed about 26percent before the ear perceives achange. But the ear won't notice asubsequent series of volume in-creases unless each increase in-cludes an additional 26 percentadded to each previous increase.In other words, the process mustproceed in an exponential manner.
For example, assume that an"average" human ear can detect areference sound level of 1mW,which we can arbitrarily call zerodB. This level would have to beincreased to 1.26mW (or about1dB) before the ear could detect achange. Then the volume wouldhave to be increased to about1.6mW (or to 2dB) before anotherchange is noticed. At the 17th in -
TABLE 2MULTIPLICATION &
DIVISION USINGPOWERS OF TEN
MULTIPLICATION.Rule-Add the exponents algebra-
icallyExample -50 microamps x 10K ohms.
50 x 10-6x 10 x 103
500 x 10-s - .5 volts
DIVISION:Rule-Algebraically subtract the ex-
ponent of the denominator from the ex-ponent of the numerator
Example -1000 volts divided by 25 Kohms,
1 x
25 x 103 1/25 .04 amps
SLUARING:Rule-Multiply the number by itself
and double the exponentExample -2000 volts squared divided
by 100 ohms,12 x 103)2 4 x 106 4 x 104
1 x 102 1 x 102 1
40 K watts
S]UARE ROOTS:
Rule-Extract the square root of thenumber and divide the exponent by 2
Example-The square root of (20 K ohmstimes 50 microfarads).
J20 K ohms x 50 microfarad -
N2 x 104 x 50-6 = 2 x 50 x 10-2
100x10-2= 10 x 10-1 = 1
JULY 1975. ELECTRONIC TECHNICIAN/DEALER / 29
TABLE 3
COMMON LOGARITHMSProportional Parts
N 0 1 2 3 4 5 6 7 8 9 2 3 4 5 7 8 910 0000 0043 0086 0128 1 0170 0212 0253 0294 0334 0374
,14 8 12 17 21 2 29 33 37
11 0414 0453 0492 0531 0569 0607 0645 0682 0719 0755 4 8 11 15 19 2 26 30 3412 0792 0828 0864 0899 0934 0969 1004 1038 1072 1106 3 7 10 14 17 2 24 28 3113 1139 1173 1206 1239 1271 1303 1335 1367 1399 1430 3 6 10 13 16 1 23 26 2914 1461 1492 1523 1553 1584 1614 1644 1673 1703 1732 3 6 9 12 15 1 21 24 27
15 1761 1790 1818 1847 1875 1903 1931 1959 1987 2014 3 6 8 11 14 1 20 22 2516 2041 2068 2095 2122 2148 2175 2201 2227 2253 2279 3 5 8 11 13 1 18 21 2417 2304 2330 2355 2380 2405 2430 2455 2480 2504 2529 2 5 7 10 12 1 17 20 2218 2553 2577 2601 2625 2648 2672 2695 2718 2742 2765 2 5 7 9 12 1 16 19 2119 2788 2810 2833 2856 2878 2900 2923 2945 2967 2989 2 4 7 9 11 1 16 18 20
20 3010 3032 3054 3075 3096 3118 3139 3160 3181 3201 2 4 6 8 11 1 15 17 1921 3222 3243 3263 3284 3304 3324 3345 3365 3385 3404 2 4 6 8 10 1 14 16 1822 3424 3444 3464 3483 3502 3522 3541 3560 3579 3598 2 4 6 8 10 1 14 15 1723 3617 3636 3655 3674 3692 3711 3729 3747 3766 3784 2 4 6 7 9 1 13 15 1724 3802 3820 3838 3856 3874 3892 3909 3927 3945 3962 2 4 5 7 9 1 12 14 16
25 3979 3997 4014 4031 4048 4065 4082 4099 4116 4133 2 3 5 7 9 1 12 14 1526 4150 4166 4183 4200 4216 4232 4249 4265 4281 4298 2 3 5 7 8 1 11 13 1527 4314 4330 4346 4362 4378 4393 4409 4425 4440 4456 2 3 5 6 8 11 13 1428 4472 4487 4502 4518 4533 4548 4564 4579 4594 4609 2 3 5 6 8 11 12 1429 4624 4639 4654 4669 4683 4698 4713 4728 4742 4757 1 3 4 6 7 10 12 13
30 4771 4786 4800 4814 4829 4843 4857 4871 4886 4900 1 3 4 6 7 10 11 1331 4914 4928 4942 4955 4969 4983 4997 5011 5024 5038 1 3 4 6 7 10 11 1232 5051 5065 5079 5092 5105 5119 5132 5145 5159 5172 1 3 4 5 7 9 11 1233 5185 5198 5211 5224 5237 5250 5263 5276 5289 5302 1 3 4 5 6 9 10 1234 5315 5328 5340 5353 5366 5378 5391 5403 5416 5428 1 3 4 5 6 9 10 11
crease of the original level wewould be at the 17dB or 50mWoutput level. At the 30th increase(or 30dB level) the power outputwould have soared 1,000 times-to the 1W level. Hence, the natureof the human ear, which respondslogarithmically, has established apractical system for measuringpower gains and losses.
Practical dB Formulas
Perhaps the most useful dBformula employed in our work,especially in audio, is that usedwith power and known as the dBmformula. In most electronic work,dBm is an arbitrary "referencesystem" in which zero dBm is1mW (1 milliwatt) of power de-veloped by 0.7746 volts across aresistance of 600 ohms. The stan-dard power dB formula is written:dB = 10 log P. This means simplythat dB equals 10 times thelogarithm of P2 divided by P1.
The best way to understand thedBm process is first to apply itsbasis to Ohm's power formula:
RE' 0.7746' o. x x 10. I.,600600 imwNext, assume that we have apreamp or amplifier that requires
a 1mW input to produce 2W out-put. We want to know the dBmgain of the amplifer. So, dBm = 10log = 10 log 2-",1(o-' = 10 log 27°= 10 x 3.3010 = +33dBm. If P2 isgreater than P1, a gain results andis expressed as + dBm. If P2 issmaller than P1, a loss results andis expressed as -dBm. Let's dou-ble the power output to 4W: 10 log14nwiw = log 4000 = 3.6021 x 10 = 36dBm. Note that by doubling thepower we increased the dBms by 3.This 3dB increase is one basiccharacteristic that should be re-membered about doubling power.
If power is increased 10 times,the dBm equivalent increases by+10. This is another basic charac-teristic that should be remem-bered.
When figuring amplifier gainby the dBm formula you fre-quently might be confronted withan input specified in millivolts in-stead of milliwatts. For example, amanufacturer says that with aninput of 4mV to a certain preampstage, his amplifier produces a10 -watt output. We want to knowthe overall amplifier gain in dBm.Assuming that the function
generator sine -wave output ismeasured across 600 ohms at 4mVon an RMS-reading TVOM, it ispractical to assume 4mV as zerodB and convert it to power with P= Ez Once the voltage readingR
is converted to power, you can pro-ceed with the regular formula forfinding dBm gain.
One practical advantage of thedBm formula, in which 1mW isalways P1 or the input, is the easeof determining the dBm gain orloss. Since log 1 (one) is zero, youneed only determine the log of P2and multiply by ten (move the dec-imal one place to the right) to ob-tain + dBm.
Simplifying Procedure
Because 10 times the log of theratio of the input and output pow-ers is either plus or minus dBm, bysubtracting the log of P1 from P2you can eliminate the operation ofdividing P2 by P1.
For example, an amplifier hasan input (P1) of 1mW and an out-put (P2) of 10 watts. Thus ,Inrw =io 10 -lox 10. 10,000
001 1 x 10" 1 1The ratio
is 10,000 to 1. The log of 10,000 is4.0000, and 10 x 4.000 is
30 I ELECTRONIC TECHNICIAN/DEALER, JULY 1975
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+ 40dBm. Let's increase the input,P1, 10 times. The log of P2 (10,000)remains the same, but P1 has beenincreased from 1 in the ratio to 10and the log of 10 is 1.0000. So,4.000-1.0000 = 3.0000 x 10 =+30dBm.
Zero And Negative dBm
The preceding has brought us tothat much used by misused andmisunderstood twilight -zoneknown as OdB, or reference level.For example, = log 10 - log10 = 1.000 - 1.000 = 0.
If the input (P1) is increased bya factor of 10, the ratio becomes:
10 wattt Log 10, as before, is 1.000011)0 wat
and log 100 is 2.0000. We havenow arrived at that area of "lessthan nothing," or - dBm. At firstglance, it might appear that1.0000-2.0000 would give us-9.0000 x 10 = - 90dBm. But thiscan not be true because the inputhas been increased according topowers of 10 and should have aratio accordingly, or 0.1:1.
At this point, if you do not al-ready know, you must learn tomanipulate logarithms in thenegative area, which involvesmerely observing simple algebraicprinciples and certain rules oflogarithms. In the preceding prob-lem, the log characteristic of 0.1 is- 1. In common logarithms themantissa (the decimal fraction tothe right of the decimal, as pro-vided in common log tables) mustremain positive. The characteristic(the number to the left of the deci-mal) can be either positive or nega-tive. Additionally, for conveniencein figuring you can add 10 orhigher multiples to negativecharacteristics if you subtract the
TABLE 4DECIBELS
Current or Voltage Ratio Power
Gain
Ratio
LossdB Gain Loss0 1.000 1.000 1.000 11.0000
1.0 1.122 .8913 1.259 .79432.0 1.259 .7943 1.585 .63103.0 1.413 .7079 1.995 _50124.0 1.585 .6310 2.512 .39815.0 1.778 .5623 3.162 .31626.0 1.995 .5012 3.981 .25127.0 2.239 .4467 5.012 .19958.0 2.512 .3981 6.310 .15859.0 2.818 .3548 7.943 .1259
10.0 3.162 .3162 10.000 .100020.0 10.000 .1000 100.00 .010030.0 31.620 .0316 1000.00 .001040.0 100.000 .0100 10.000 .000150.0 316.200 .0031 100,000 C0010
same amount at the end. Forexample: ;t,7, = (log 10) - (log100) = (1.0000 + 10) - 2.0000 =11.0000 - 2.0000 = 9.0000 - 10 =-1.0000 x 10 = - 10dBm.
If we turn this last problem up-side down so that we have a 10watt input (P1) and a 100 wattoutput (P2) we will come up with+10dB, or the opposite "image" of-- 10dB.
Finding Power With dBm Given
We have the dBm zero referencegiven (P1 = 1mW) and the output(P2) given is + 40dBm. We want toknow the output power (P2). P2 =antilog dtBom = anti log 40r=4. An-tilog 4 = 10,000mW = 10 watts.
And on the minus (loss) side: P2= antilog 51111-m- = - 4. Antilog -4= 0.0001mW = 0.1µW = 1.00nW.To check the preceding computa-tion: - dBm =10 log =log 100 = 2.0000 + 10 = 12.0000 -6.0000 (log 106 nW) = 6.0000 -10= log - 4.0000 x 10 = - 40dBm.
The above formula for convert-ing - dBm to power when thespecified - dBm (the numerator) isnot evenly divisible by 10 must berevised somewhat to provide accu-rate results. Likewise, when a dif-ferent zero reference, say 6mW, isused, the formula is revised to: P2= 0.006 x antilog .
Voltage/Current dB FormulasA manufacturer's specs say an
amplifier has a 0.5V, or 500mV,input which provides an output of25V. Disregarding impedances,what's the dB voltage gain? dBV =20 log E' = 20 log '551=vv = log25,000 - log 500 = 4.3980 -2.6990 = 1.6990 x 20 = 34dBV.
The dBmV (or d13µV) system isparticularly useful for dealingwith antennas, especially MATVsystems. This method employs azero reference of 1,000 microvolts,or lmV. With it, computations arelimited principally to algebraic-ally adding the gains and losses ofthe various active and passiveelements in the system, whetherlarge or small. By employing thismethod, a "finger-tip" check canbe maintained throughout thesystem planning and installationprocedure so that each TV and FMoutlet will be provided with suffi-cient signal, which for TV sets isnormally considered to be lmV (or1,000 microvolts) for adequatecolor TV reception. III
32 ELECTRONIC TECHNICIAN/DEALER, JULY 1975
Your VTVM is obsolEtE!This may sound like a harsh
claim, but it's true. Thousands of TVtechnicians are using instrumentsdesigned in the 1950's to trouble-shoot circuits designed in the 1970's.
And now, most color TV's havesolid state circuits. So use ofout-of-date test equipment justcompounds the problem.
The generation gap has growntoo big.
The Fluke 8000A 31/2 digit multimeter
Solid state calls for newperformance standards.
Your "old fashioned" test equip-ment simply doesn't measure up totoday's requirements. For example,the typical VTVM gives you 5%accuracy and 2% resolution. In theold days, that was good enough.Not so today.
Now you need an instrument tolook at the voltages at each pin of anIC with sufficient accuracy andresolution to determine proper ICoperation.
For example, a reading of "around2.8 volts" is no longer sufficient.You must be able to distinguishbetween 2.80 and 2.82 volts.
You need a test instrument thatgives you 0.1 ohm resolution so youcan reliably measure resistance ofswitch contacts, circuit breakers,and low value resistors.
To do all this and more, you needthe superior capabilities of theFluke 8000A 31/2 digit multimeter.
An instrument designed specificallyfor testing solid state equipment.
The 8000A gives you up to 50times the accuracy and 20 times theresolution of a VTVM, so you canmeasure the various voltage levelsin a solid state chassis withabsolute confidence.
1710r--
SU-L. COMMON
ICI IC MN
I I0111111allarri I 1
rINCTIIN NANCE galNCI IC MA NC 2110 ina 2 21 211 mato
1101Illi MULTI
POWER
ON -01F
Resolution is 100 microvolts, 100 nanoamps and 100 milliohms
You get the sensitivity you needfor low level dc measurements. The200 millivolt range with 100 microvoltresolution tells you exactly whatyour values are.
The 8000A has an AC frequencyresponse from 45 Hz to 20 KHz and,with accessory probes, to 500megahertz. Resistance measuringcapability ranges from 100 milliohmsto 20 megohms. It offers a 15°C to35°C accuracy temperature span.And a 1 -year accuracy time span,meaning it seldom needs calibration.
Unlike other DMM's the 8000Ahas fast response time -3 readingsa second. And the bright, digitalreadout means that no interpolationis necessary.
The 8000A measures highvoltages, too.
Our 8000A is designed to answerall the needs of an electronic servicetechnician.
One very important (and talkedabout!) safety requirement is that thepicture tube anode voltage mustnot exceed the maximum specifiedby the manufacturer. Our 8000A hasan optional high voltage probe thatgives you guaranteed accuracy of1% at 25,000 volts. The probe alsoextends the capability of the 8000Ato 40,000 volts to measure the highvoltage in the new 32,000 voltchassis.
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High voltage probe accessory givesyou 1% accuracy at 25,000 volts
For data out today, dial our toll -free hotline, 800-426-0361
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Get the most up-to-date instrumentavailable.
Don't be caught in the typical trap.Many electronic service shops don'treally update their equipment whenthey decide to update. Switchingto a TVM or a FET voltmeter doesn'treally give you the accuracy andresolution you need today, or forthat matter, tomorrow.
But with the 8000A on hand, youknow you have a true solid statetesting device ... an instrumentthat can do the job the way it shouldbe done.
Carry it anywhere. Use it on line or withoptional rechargeable battery power.Note the conveniently mounted specson the bottom decal. They're alwayswith you.
The 8000A comes from Fluke, oneof the largest instrument companiesin the U.S.
It costs just $299 ($40 more withHV probe). * And it is far and awaythe largest selling, most rugged andreliable 3V2 digit multimeter inthe world. Domestic only.
FLUKEJULY 1975, ELECTRONIC TECHNICIAN/DEALER 33
Circle #111 for information, circle #112 for demonstration
Power SupplyRegulator Circuits
How they function and how to service them
By Joseph J. Carr, ET, D Contributing Ed for
There are a number of reasonswhy equipment manufacturers goto the expense of incorporatingregulated DC power supplies intotheir equipment. In FM receivers,for example, the local oscillatorwill drift all over the band if anunregulated power supply is used.This is why most FM receivers usea regulated supply at least in thetuner stages.
On the other end of the spec-trum are certain audio amplifierdesigns which are able to operatewith lower distortion when regu-lated voltage sources are used tosupply the driver and pre -driver.
Another aspect of regulatedsupply application is the inherentreduction of power supply ripplecomponent in high -gain audioequipment. The source of suchripple is rectification of AC sinewaves. Fig. 1 graphically demon-strates the superior ripple reduc-tion of a solid-state regulatedpower supply. Both traces weretaken using the same "volts/div."factor for the vertical amplifiers.The upper trace is the waveformwhich appears across the output ofthe diode rectifier. From this pointto ground there was a 250-mfdelectrolytic capacitor. The lowertrace was taken using the sameoscilloscope deflection factor, butfrom the output of the regulator.
Note that although the input voltage to the regulator exhibits about240 millivolts of ripple, there ispractically none at the output. Itwould take a very large capacitorto reduce ripple this much in aconventional power supply circuit.In fact, one manufacturer of autoradio bench power supplies, Delco,used to advertise that their "elec-tronically regulated" power sup-ply has the equivalent of 1.0 faradof filtering. What they meant wasthat electronic regulation reducedripple to a level that would haverequired a liarad filter capacitorfor comparable ripple reduction ina conventionally designed powersupply.
Regardless of the type of equip-ment being serviced, I have foundthat odd and/or multiple troublesymptoms occur when incorrectvoltages and/or excessive rippleare applied to circuits. This hap-pens so often that I have made it astandard procedure to use both avoltmeter (amplitude) and a scope(ripple) to check power supplieswhenever odd, unusual or multi-
symptom situations are encoun-tered.
THE NEED FOR REGULATION
There are two basic reasons whythe output voltage of a power sup-ply will vary: 1) changing input
Fig. 1-Top waveform reveals 240mV of ripplepresent at a point immediately preceding thevoltage regulating circuit of a power supply. Bot-tom trace. taken at the output of the regulatorcircuit, reveals the significant reduction of ripplewhich a regulator is capable of achieving. Bothtraces were taken with a dual -trace scope withboth vertical amplifiers set for equal gain.
(INTERNALoi RESISTANCE
OF POWERSUPPLY)
VOLTAGE- SOURCE(SUPPLY)
I(LOAD
CURRENT)
E OUT R2(RESISTANCEOF THE LOAD)
E OUT = E_( R2 _)R R'Z
Fig.2-Equivalent circuit of a power supply andits load. R1 represents the internal resistance ofthe power supply itself and R2 represents thevarying resistance of the circuits to which thepower supply furnishes operating voltages. Alsoshown is the formula for computing the voltageoutput of a supply.
voltage, and 2) changing outputload conditions. The former isespecially a problem in automo-tive electronics and in those areaswhere the power mains are over-loaded.
The latter problem, changingload conditions, can be better un-derstood by referring to Fig. 2. Allpractical power supplies can berepresented by an "ideal" voltagesource, which has zero internalseries resistance, and a series re-sistor (R1) which represents thetrue series resistance of an actualsupply.
The total variable resistance ofthe various individual circuitswhich the power supply feeds inparallel is represented in Fig. 2 bya single variable resistance, R2,which is in series with the internalresistance (R1) of the supply. Be-cause the conduction of the stagesrepresented by R2 varies, so dotheir individual resistances andthe resultant current drain (load)on the power supply. When thevalue of R2 decreases (increased
34 / ELECTRONIC TECHNICIAN/DEALER, JULY 1975
R1 A
E UNREGULATED E REGULATED
1/1
R2
E UNREGULATED
I iE REGULATED
R3 1.
E UNREGULATED E REGULATED
D1
Fig.3-Three basic types of shunt regulator devices: A) gas regulator (0A2, 0B2, etc.), B) Neonglow lamp (NE -2, NE -51, etc.), C) Zener diode.
current drain, or load), the outputvoltage of the supply also de-creases, as will be verified if youmentally plug various values intothe voltage output formula inFig.2.
To prevent the output voltage ofthe supply from decreasing as thecurrent drain (load) increases, it isnecessary to maintain a constantratio between the internal resis-tance of the power supply (R1) andthe load resistance (R2). Forexample, if R2 decreases (in-creased load, or current drain), thevalue of R1 should be made to ef-fectively decrease a proportionateamount, so that the output voltageof the power supply will remainrelatively constant. This is voltageregulation.
Such regulation can be ac-complished by two basic methods:
1) A variable resistance whosevalue automatically adjusts tochanges in the load of the powersupply can be placed in parallel toR2 so that as R2 decreases (loadincrease) the parallel variable re -
E
VzI
I
E
Fig. 4-Current-vs-voltage character stics of a Fig. 6- Typical IC -equipped power supplytypical Zener diode. regulator circuit.
Fig. 5-Series-pass regulator circuit.
sistance increases a proportionateamount, to keep the effectivevalue of R2 relatively constant.
2) A variable resistance whosevalue automatically changes in-versely to changes in the powersupply load can be placed in serieswith R1 so that as the value of R2decreases (increased load) the ef-fective total value of R1 and theadditional series resistance alsodecreases a proportionate amount,to maintain a constant ratio be-tween the values of R1 and R2.
BASIC SHUNT -TYPEREGULATING DEVICES
Fig. 3 shows several shunt -typedevices used to regulate powersupply outputs. Fig. 3A is a cold -cathode gas tube, which was usedfor many years in vacuum tubeequipment. Fig. 3B is anothergas -type regulator, a neon glowlamp.
Both of these types of gas -filleddevices provide regulation be-cause the voltage drop across anionized gas cell tends to remain
U1
E E OUT
0
GROUND INTERRUPTED AT "X" FORSERIES POTENTIOMETER TO TRIM
EOUT IN SOME CIRCUITS
Fig. 7-Three-terminal voltage regulator de-vice. Because some are packaged in TO -typetransistor cases, they often are mistaken fortransistors.
constant even though the currentthrough it changes.
In other words, the internal re-sistance of a gas regulator changesinversely when the voltageapplied changes.
Fig. 3C is another type of shuntregulator device, the Zener diode.These devices have a peculiarvoltage -current characteristiccurve, which is shown in Fig. 4.Note that when the PN junction ofthe diode is forward biased, thecurrent flow is identical to that ofany solid-state diode. However,when the Zener diode is reversebiased it operates somewhat dif-ferent than a conventional solid-state diode. When a normal PNjunction is reverse biased, no cur-rent flow occurs. In a Zener diode,this is true only up to the pointwhere the reverse -bias voltagereaches a critical value known asthe Zener voltage. When this volt-age is applied to the junction, it"breaks down" and begins con-ducting current.
Between zero volts and Vz, the
JULY 1975, ELECTRONIC TECHNICIAN/DEALER / 35
Zener diode exhibits the large re-sistance associated with anyreverse -biased semiconductordiode. At voltages from the Zenerpoint on up, though, the Zenerdiode has a very low resistance.This characteristic allows theZener to be used as a shunt -typeregulator, provided that the seriescurrent can be limited to a safevalue by .R3. Although it tends tochange slightly with changes intemperature, Vz is stable enoughto provide relatively good regula-tion.
SERIES -PASS REGULATING CIRCUITS
When either critical stability ormore flexibility is needed, otherregulation techniques and circuitsare used. Some are discrete transistor circuits (Fig. 5), whileothers use either special ICs (Fig.6) or three -terminal devices (Fig.7).
One popular IC regulator, theUA723, comes in several packagestyles and is flexible enough to befound in a wide variety of equip-ment.
Three -terminal regulators arerelatively new but already arebeing used in consumer electronicequipment. Because they come inTO -3, TO -66 and plastic transistorcases, they can easily be mistakenfor transistors. If service informa-tion is not available, circuit loca-tion and the lack of other compo-nents (such as a Zener diode andresistor at the "pseudo -base" ter-minal) are the best means of iden-tifying a three -terminal reg-ulator. This can be an especiallyaggravating problem if the setmanufacturer uses "house num-bers" to identify semiconductorsand yet offers inadequate servicedata.
Fig. 5 is a series -pass transistorregulator. Note that regulator ac-tion in the series -pass design is ac-complished by effectively raisingand lowering the resistance of theseries -pass element of the reg-ulator circuit.
This circuit increases the cur-rent range of the regulator and"amplifies" the regulating effectsof the Zener diode which is used tostabilize the transistor base. Be-cause collector -emitter resistanceis dependent on base -emitter bias,
Fig. 8-This series -pass type of regulator circuitis s miler to that in Fig. 5 except that a secondtransistor. 02. is used to control the base ofseries -pass transistor 01 instead of it being controlled directly by Zener diode D1. This circuitarrangement provides closer regulation thanthat in Fig. 5.
Fig. 9-A series -pass regulator circuit which iscontrolled by a differential operationalamplifier.
the base of Q1 is held at a fixedvoltage by Zener diode Dl. Whenthe demand for output load cur-rent decreases, the emitter volt-age increases, causing the base -emitter bias to decrease slightly.This, in turn, causes the transistorto pass less current, thereby effec-tively increasing the collector -emitter resistance in series withthe load.
When the demand for load cur-rent increases, the emitter voltagedrops and, because this increasesthe forward bias of the base -emitter junction, the transistorconducts even harder. This, inturn, lowers the collector -emitterresistance, causing the outputvoltage to increase back to thesteady state value.
For a regulator equipped withan NPN transistor, the steadystate output will be close to (Vz +
E IN
RI
E SOURCE
O
GISERIES -PASS
AMPLIFIERCONTROLAMPLIFIER
COMPA-RATOR
R S
REFERENCESUPPL
D2
A
EOUT
-0
SENSE AMPLIFIERHERE. IF USED
03 D.
Fig. 10-Block diagram of a more complicatedseries -pass regulator (A). in which a reference(B) is compared with the output voltage.
Fig. 11-A switching, or flyback. type of reg-ulator (A). which uses a variable duty cycleswitching system to control the output voltage. Asimplified illustrative schematic of this systemis shown in (B).
Vbe) or (Vz + 0.7). For a regulatorequipped with a PNP transistor,the steady state output voltagewill be about 0.7 volts lower thanthe Zener voltage (Vz). This is agood guide for selecting replace-ment Zeners in the absence ofcross-reference data.
Figs. 8 and 9 show similar butmore complex designs of series -pass regulator circuits. A secondtransistor, Q2, with a Zenerstabilizing its emitter voltage, isused in Fig. 8 to control the base ofthe series -pass transistor Ql. A
36 / ELECTRONIC TECHNICIAN/DEALER, JULY 1975
RECTIFIER
110 V,!1_60HZ
CHOPPERs
LC FILTERGCS r- - -
L
WEEPER
DRIVER
RUE StWIDTH
MODRATOR
ER ORAMP
130 V REGULATED
r
Fig. 12-Block diagram of the switching type of power supply and regulator used in Sony's KV-1722Trinitron color TV receiver.
REGULATOR
_L CIRCUITS
SCR1RD
RD
EA EOUTRRt ,2
E OUT
Fig. 13-SCR "crowbar" protection circuishown here blows fuse if either the series -passtransistor or Zener fail in a way that causes anexcessive output voltage.
REGULATED POWERSUPPLY FAILURES
(Based on 37 IndividualIncidences)
COMPONENT TOTAL PERCENTAGE
WHICH NUMBER OF TOTAL
FAILEDZener Diode 17 46%Series -PassTransistor 14 38
All Others * 6 16
'Four of these were the "other" transistor in cir-cuits such as Fig. 8.
sample of the output voltage, inturn, drives the base of Q2 viavoltage divider R1 and R2.
The circuit of Fig. 9 uses a Zener(D1) to stabilize one input of a dif-ferential IC operational amplifier(U1), while a sample of the outputvoltage is applied to the other dif-ferential input via voltage dividerR1 and R2. The output voltage,which controls the base of theseries -pass element, is propor-tional to the differential inputvoltage.
COMBINATION REGULATORS
Regulated power supplies comein several varieties, and you canexpect to see more than one type insome equipment. For example, a
recent color TV chassis and sev-eral FM receivers use a simpleZener to regulate some voltages,but for regulation of more criticalvoltages, they use a series -passtransistor or op -amp design.
More complex equipment, ofcourse, requires more complexregulators. An example of such aregulator is block diagrammed inFig. 10A. Q1 is the same type ofseries -pass transistor used in lesssophisticated circuits. Its base,however, is controlled by anamplifier (either discrete transis-tor or IC) driven by a voltage com-parator circuit. Output currentgenerated by the control amplifieris steady as long as the referencevoltage (Fig. 10B) and the outputof voltage divider Rl/R2 (or senseamplifier) are equal. Changingload conditions, however, makethe output of voltage dividerR1/R2 vary, which causes thecomparator to either increase ordecrease the output of the controlamplifier.
SWITCHING REGULATORS
Fig. 11 shows the block diagramof a modern, very efficient powersupply called the switching reg-ulator or flyback regulator. Fig.11B is a simplified version.
Consider the electrical situationacross the load in Fig. 11B whenswitch S1 is closed. Output voltageis zero and the current is limitedonly by any series resistance inthe power source or inductor Ll.During this period, energy isstored in the magnetic fieldaround Ll. When S1 is opened,this field collapses and dumps acountervoltage into the circuit,producing an output voltage equalto the source voltage plus thecountervoltage. This voltage willdecay to the value of the source
voltage if the switch is left openlong enough for the field to dis-charge completely.
In actual circuits, switch S1 willbe a shunt transistor such as Q1 inFig. 11.A. A multivibrator or oscil-lator supplies a pulse train whichdrives a pulse width modulator(PWM) to electronically "toggle"Q1. Use of a PWM causes theon/off state (duty cycle) of Q1 tovary in response to changes in theoutput voltage.
Sony uses a switching powersupply in their KV1722 and otherTrinitron chassis which is similarbut not identical to the circuit ofFig. 11. A partial functional dia-gram of the KV-1722 switchingpower supply is shown in Fig. 12.The electronic switch is a SiliconeControlled Switch (SCS) whichSony calls a Gate ControlledSwitch, or GCS. This device is aPNPN switch which behaves simi-larly to a flip -flop -connectedPNP/NPN pair (hence the two -arrow symbol). Each "transistor"in the pair regeneratively drivesthe other, causing an increased,more nearly perfect, switchingtime. A low-pass filter at the out-put of the supply reduces the prob-ability of hash from high -frequency switching transients,which would interfere with othercircuits.
TROUBLESHOOTING PROCEDURES
Troubleshooting the more com-plex regulators can be tricky be-cause they are negative -feedbackcontrol circuits. Once you are cer-tain that the reference voltagesource is operating normally,check the series -pass element.After that, test the rest of thesemiconductors.
Analysis of one month's servicerecords kept by one service shopwith which I am familiar revealsthat in 37 repairs of regulatedpower supplies the componentfailures by percentage of typewere as shown in the accompany-ing table. From this table it can beseen that the fastest approach totroubleshooting is to check thehigh -failure -rate items after firstdetermining that the referencevoltage source (if used) is function-ing normally.
Then check the negative feed -
JULY 1975, ELECTRONIC TECHNICIAN/DEALER / 37
back aspect of the circuit.One word of caution regarding
equipment equipped with supplieswhich come in with a blown fuse:don't replace the fuse and turn onthe set until the series -pass ele-ment and the Zener have beenexamined. The reason for this pre-caution is that some regulatorsare equipped with a protection cir-cuit, like that in Fig. 13, whichblows a fuse whenever excessivevoltage appears at the output.This circuit remains inert as longas the sample of the output voltageat point "A" is too low to supply asufficient current through R3 totrip the gate of the SCR. If theregulator should fail in a mannerwhich places excessive voltage ac-ross the output, a larger currentwill flow in R3, and the SCR willbe gated on. This causes theanode -cathode resistance to dropto a fraction of an ohm, drawingenough current to pop fuse Fl.
Some technicians merely checkthe output line with an ohmmeterand, if no short is found, they re-
place the fuse and try a "smoketest." The only trouble is that,after blowing the fuse, the SCRand all other circuits return totheir normal "off" conditions (ex-cept for the fuse and the failedcomponent.) Once the fuse is re-placed without finding the cause,the whole cycle repeats itself.
One of my early employers, Nel-son Moodie, of Colonial Radio inArlington, Va., used to have a say-ing (among many): "Fuses don'tcause trouble, they indicate trou-ble!" Moodie's admonition goesdouble for SCR "crow -bar" pro-tected supplies such as that in Fig.13.
Another difficulty encounteredin the servicing of regulatedsupplies is the possibility that ashort in the equipment, not in thepower supply itself, caused thefailure of the supply circuits. Toeliminate this possibility, use abench supply, or combination ofsupplies, if needed, to substitutefor the set's supply long enough totest the rest of the circuitry. These
supplies, which are available froma number of sources, includingRCA, Heath and Kepco, includecurrent -limiting protection. Dis-connect the set's power supply(even if this means a razor cut onthe PC foil) and connect in the"outboard" power supplies.
Once you are satisfied that theset is working, replace the defec-tive components and reconnect theset's internal power supply.
CAUTION: Should you tryusing two or more electronicallyregulated bench supplies in paral-lel to increase their current capa-bility, you might run into a prob-lem whereby the two supplieskeep fouling up each other's volt-age sensing circuits. In one type ofsymptom, the breaker of one sup-ply will trip and the other will beforced to supply all current re-quirements.
Another symptom occurs withsupplies equipped with auto -resetbreaker. Supply A will shut downSupply B, which shuts down A,which shuts down B, etc.
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TEST INSTRUMENT REPORT
.000 KM
A diode and three fuses protect the TriplettModel 60 from overload damage. For more in-formation about this instrument circle 100 on theReader Service Card.
TRIPLETT MODEL 60 VOM
The most important interestingfeature of Triplett's Model 60VOM is its ability to withstandmisuses and hard everyday servic-ing needs.
The instrument has built-inprotection against accidental highenergy overload, is shock resistantto accidental drops up to a five footheight, modular constructed sothat it can be quickly serviced inthe field, and is designed to meetrigid safety standards to preventelectrical shock.
After throwing the instrumenton the floor a few times and apply-ing an AC input voltage, with theinstrument set to the ohms range,no detectable harm was noted tothe instrument or its accuracy. Wewere quite convinced it could takea lot of abuse.
Safety Features
To help eliminate destructionfrom accidental drops, the instru-ment features a case of moldedblack, high impact thermoplasticmaterial, in combination with asuspension meter module whichliterally floats inside the outercase. The case finish has a non -slip"finger -tread" surface finish forhandling ease.
The meter movement is pro-tected by a diode module and toprevent harm from normal over-
Triplett's Model 60 VOM is shock -resistant toaccidental drops up to five feet
load conditions it is protected by a2 amp, 1000 volt (20 KW on DC; 30KVA on AC) fuse and two zenersare used to protect the instrumentagainst high energy fault currentsand provide protection of the test-er circuits up to 1000 volts.
A separately sealed batterycompartment permits external ac-cess to the batteries and fuseswithout removing other parts ofthe instrument. Also found in thiscompartment are a spare 1/8 ampand 1 amp fuses. There are no ex-posed parts, this design insulatesthe user from the instrument it-self. It also provides an internalelectrical system which preventsexplosive arcs in high energy cir-cuits up to 2 amps, 1000 volts fusecapacity. The test lead jacks on thefront panel are recessed safetyconnectors and a large imprintedlabel spelling out the safety pre-cautions to observe when usingthe instrument are additionalsafety features.
Construction Features
The instrument employs a 45 µasuspension movement with a 41/2inch scale. It is contained in aseparate protective housing ofmodular design which can be re-
moved and replaced in a shorttime in the field if necessary. Onlytwo connecting wires require re -soldering to put the tester backinto operation. The removal ofeight screws completely disas-sembles the instrument.
The single range selector switchhelps to prevent incorrect settingsand enables you to select any oneof the 28 ranges. The scale in-cludes markings for direct read-ings when employing the optionalClamp -on AC Ammeter.
Also featured is a special"Confidence -Test" feature whichis built into the unit for periodicreassurance checks of its meter.
Measurement Ranges
DC Volts. Ranges: 0-1, 3, 10, 30,100, 300, 1000 Volts at 20,000Ohms/Volt. ± 2 percent of fullscale all ranges. AC Volts. Ranges0-3, 10, 30,100, 300, 1000 Volts at5000 Ohms/Volt. Accuracy is + 3percent of full scale all ranges. DCCurrent Ranges: 0-0.1, 10, 100,1000 Milliamperes at 320 Mil-livolts. Accuracy is + 2 percent offull scale all ranges. ResistanceRanges: 0-1K, 10K, 100K, 1M,10M, (12, 120, 1.2K, 12K, 120Kohms center scale). Accuracy is +2 percent of arc length. Decibels.Range: -20 dB to +52 dB Accu-racy is + 2 per cent of full scale allranges. Output volts (AC) Ranges:0-3, 10, 30, 100, 300 volts at ap-proximately 5000 ohms/volt. Ac-curacy is + 3 pecent of full scale allranges.
The instrument measures ap-proximately 31/4 inches by 51/4inches by 71/4 inches and weighs2% pounds with batteries (1-9 volt,and 1-1/2 volt "D" cell).
The instrument comes completewith safety test leads, insulatedalligator clips, batteries, spare 1/13amp and 1 amp fuses and instruc-tion manual. Price is $90.
LECTROTECH MODEL TO -60OSCILLOSCOPE
There are growing needs for adual -trace oscilloscope in thehome entertainment equipmentservicing. The dual trace scope,used in industry and labs for manyyears, is appearing on servicebenches with increasing numbers.
Lectrotech's Model TP-60 solid
40 / ELECTRONIC TECHNICIAN/DEALER, JULY 1975
Lectrotech Model TO -60 Automatic Dual -TraceOscilloscope. For more information about thisinstrument circle 102 on the Reader ServiceCard.
state, 15 MHz, dual trace trig-gered sweep, oscilloscope permitsdual display of waveforms in fivemodes, allowing you to comparethe waveforms for shape, ampli-tude and time duration.
Features
Automatic Triggering Sweeptriggers solidly on all signalswithin the rated band width. Au-tomatic Astigmatism Spot defini-tion is always clean and sharpover entire CRT screen. Automa-tic Horizontal Sweep Special cir-cuit provides free -running hori-zontal sweep in absence of trigger-ing signal in the ground/free-runposition. The time base remains athigh brightness for all sweepspeeds. Automatic Horizontal!Vertical Triggering. When view-ing video signals, the horizontaland vertical triggering is selectedautomatically by the time baseswitch.
TV trigger selector automati-cally converts the trigger amplifi-er to an amplitude selectable SyncSeparator. This feature providesstable triggering on composite TVvideo signals. Unique trigger cir-cuit provides automatic triggeringto frequencies in excess of 15 MHzwith as little as 1 division of dis-played signal. It is an ideal in-strument for the display of sweepalignment response curves. TheDC coupler amplifiers providemaximum stability for thesecurves and minimize the need forboth oscilloscope and sweeper ad-justments and it is compatiblewith all existing sweep genera-tors. Channel A or Channel B cantrigger independently of each
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As popular as ME Sniff is ... a lot of technicians justprefer an old fashioned solvent -lubricant. So we decidedto invent a brand new old fashioned solvent -lubricantfor them. Fi/ is unquestionaLly the finest tuner solvent -lubricant to come along. It washes clean and leaves aslick but not sticky film. And we still have BIIIE STUFF
So now you get to do it your way. ..and either way the best is from
TECHSPRAY
where we find solutions for your problems
...for more details circle 126 on Reader Service CardJULY 1975, ELECTRONIC TECHNICIAN/DEALER 41
T & T VALUE SALERAYTHEON, I.C.C.. RCA. SYLVANIA
FAMOUS MAKE, NEW JOBBER -BOXED TUBESNOW WITH NEW 5 -YEAR GUARANTEE
80% Off LIST
1V2 5 for 53.00 0 6HA5 5 for $4.802AV2 5 for $3.90 u 6HQ5 6 for $6.353A3 for 55.05 0 6H115 6 for 11.803AT2 5 for 0 8JC6 5 for $5.6530 85 5 for $4.85 0 8.1E6 6 for 11.153HA5 5 for $4.80 0 6JS6 6 for $9.303HM5 5 for $4.80 IICI EIJU8 6 for $5.555GH8 5 for $6.90 LJ EIKA8 5 for $9.15O 6AY3 6 for $5.05 0 6KE8 6 for $7.65O 6BK4 6 for $9.35 0 61(78 5 for $6.856003 5 for $4.95 10 6KZ8 6 for $5.156C08 5 for $6.40 D 6LB6 5 for 10.756CJ3 6 for $4.70 0 SLOG 5 for 11.158DW4 6 for $4.70 JI 8FQ7 6 for 3.75SEAS 5 for 54.95 0 12BY7 5 for 4.50
8FQ7 5 for $3.758EJ7 5 for $4.50 17JZ8 5 for 4.50
23Z9 5 for 6.00
6EH7 5 for 54.80 12GN7 5 for 7.00
60F7 5 for 56.65 0 33GY7 5 for $8.0560H8 5 for $3.95 0 36MC6 5 for 11.406GJ7 5 for $3.40 0 38H E7 5 for $9.20
O 6GM6 6 for $5.25 0 38HK7 6 for 9.00O 6GU7 6 for $5.25 U 42K N6 6 for 9.15
What is not advertised -write in at 80%Off List!
O One FREE 613H8 for every 5 Tubespurchased.
O A6GH8 SPECIAL 100 for $49.00ALL SYLVANIA TUBES 70 & 100/. OFF
LIST -SLEEVES ONLYTRANSISTORS XACT. REPLACEMENT (BOXED)
Up To 85% off LISTSK ECG
O 3009 102A 10 for $5.85O 3018 121 10 for $3.38O 3021 124 10 for $4.73O 3041 162 10 for $6.30O 3052 131 10 for $5.85
3054 184 10 for $8.753083 183 10 for $8.303084 196 10 for $7.203103 157 10 for $4.503114 169 10 for 53.60
O 3115 186 5 for $12.40O 3124 123A 10 for $3.15O 3132 10 for $3.90O Zen. 212-46 6 for $10.00LARGE DISCOUNTS ON ALL TEST EQUIPMENT
O B & K Precision Portable Digital Multi -meter Model 280. Reg. Price $99.95 -Our Price $85.00
DIODES & RECTIFIERSROA Damper Diode Equiv. To:
O RCA 120818 $1.35 0 RCA 185832 $2.95O 8500 PIV Color Focus Rect. 10 for $5.000 2.5 amp 1000 PIV 1R170 100 for
D1304 Zen. Voltage Trlpler 212-136 2 for 8.00
10 for 2.600
YOKES - TUNERS - FLYS EQUIV.O Y94 0 Y105 0 Y107 Y109
Y119 0 Y130 0 DY107AC 95.2779 0 Syl. 51-29978-E01O Phllco 76-14328-1 ID Philter> 76-14328-
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60 Min. Cassette Tape 12 for $4.0060 Min. Irish Cassette Tape 12 for $8.0090 Min. Cassette Noreico type box
12 for 510.0084 Min. Irish 8 -track Tape 6 for $8.0084 Min. Shamrock S -track Tape 7 for $6.0040 Min. Shamrock 8 -track Tape 8 for $4.008 -Track Head Cleaner 5 forCassette Head CleanerEmerson Mikes
10 for 4.0010 for 4.00Equly: 0 N77 0 876 8910 Shure 44 0 PickerinV15 ea. 52.95 B5R Cart. 0 132M5 Cl SKIM
E SCSM 4 for $8.0012 Asst. Needles Incl. Diamond $4.95BSR Adapters (45) 6 for S2.005 x 7 Speaker with Grill. pre -wired.3 -position Rotary Switch. ea. $2.95O 6 x 9 Speaker with Grill, pre -wired,3 -position Rotary Switch. ea. $3.95El 3 Stereo Headphones $10.00
E Universal AC Adapter. By. 75V, 9V $4.95Cl 2 of each: 4". 5", 6". 2x4", 406",3x5". all 12 for $13.96
NEEDLESO BSR 1M E 3M [Ti 5M 12 for $4.95 Tetrad TD9 Universal 12 for $4.95 Electro Voice EV 13M 12 for $4.95
ANTENNAS10 300 ohm 2 -Set Coupler 10 for 57.500 300 ohm 4 -Set Coupler 10 for $10.00O 72 ohm to 300 ohm Matching
Transformer 10 for $7.500 72 ohm Signal Splitter 5 for $5.00O 59 OF Connectors 100 for $10.00Ei 8 Antenna Clothespins $1.18
GENERALO 19 & 25" 0 21"
Color Boosters 3 for 511.95 Belfuse 2250.1 25 for $2.50 NV 30K V Anode Leads 6 for $1.290 SHUNT REG. HOODS (681(4) 3 for 51.29n Color CRT Harness 8 for $1.29
T & T SALES CO.4802 AVENUE K
BROOKLYN, N. Y. 11234Phone: (212) 241-5940
other in single channel modes. Indual channel modes the triggeringis provided by channel A.
Other features include: vec-torscope input for color TV servic-ing, external horizontal amplifier,external horizontal input, cali-brated horizontal time base, TVsync selector, and calibrated ver-tical attenuator.
Specifict3ons
Vertical Amplifier Bandwidth:DC to 15 MHz min. Risetime: 23nano seconds. Sensitivity: .01volts/div. to 20 volts/div. in 1-2-5step sequence plus continuouslyvariable control. Input Impedance1 Megohm + 1 percent shunted by30 picofarads Horizontal SweepType: Miller Integrator SweepSpeeds .2 second/per division to .5micro second/per division in 1-2-5step sequence plus continuouslyvariable control. With 5X mag-nifier sweep speed increases to 11micro second/per division. Trig-gering Source, Internal externaland line Type: Automatic oramplitude selection with presetstability External HorizontalAmplifier Bandwith: DC to .5 MHzSensitivity: .5 volt/per divisionInput Impedance: 100 K shuntedby 30 picofarads Cathod Ray TubeDisplay Area: 8 by 10 Cm Blank-ing: DC coupled.
Size and Weight
The instrument measures 9inches high by 10 inches wide by131/4 inches deep and weighs 25pounds. The price is $489.50.
SYSTRON DONNER MODEL 7004ADIGITAL MULTIMETER
The Systron Donner Model7004A Digital Multimeter is a fullfour -digit instrument. It offers thefive selectable functions of DCvoltage, DC current, AC voltage,AC current and resistance.
Some of the outstanding fea-tures of the unit include highinput impedance on the three mostsensitive ranges, extended ACfrequency response, new ease ofcalibration, and improved serv-iceability.
All function and range selec-tions are made from the front -panel pushbutton controls. Thereadout features a nonblinking
Systron Donner Model 7004A Uigital Multimeter.For more information about this instrument cir-cle 103 on the Reader Service Card.
display of four full digits plusoverrange, auto -positioned deci-mal point, and an indicator foroff -scale readings. Polarity indica-tion for DC voltage and current isautomatic with a minus indicatordisplay.
Resolution and Accuracy
All measurements are madewith 0.01 percent resolution on afull four -digit display. A fifthreadout digit allows 30 percentoverrange capability. Accuracy onthe top four DC voltage ranges is+ 0.01 percent of reading + 0.01percent of full scale from + 20 de-grees to + 30 degrees C for 30 daysminimum. To maintain accuracy,it features 1000 megohm imputimpedance on the three most sen-sitive ranges to help eliminateloading errors.
Measuring Ranges
The instrument provides 25measuring ranges. Five DC volt-age ranges and five AC voltageranges permit measurementsfrom 10 microvolts to 1000 volts(500 volts rms maximum on AC).Current measurements (both DCand AC) can be made without theneed for external shunts. Five re-sistance ranges provide readingsfrom 100 milliohms to 13 meg-ohms.
Noise Rejection
A fully floating and guardedinput circuit provides better than100 dB of common mode noise re-jection at all noise frequenciesfrom DC to 1000 Hz. To maintainaccuracy in presence of unwantedripple, or normal mode noise, itcombines the built-in noise rejec-tion characteristics of Dual -Slopeintegration with a full-time noise
...for more details circle 125 on Reader Undo Card
42 ELECTRONIC TECHNICIAN/DEALER, JULY 1975
DELO 'E DIGITAL COLOR
filter to achieve better than 60 dBof rejection at power line frequen-cies.
Portability Design
The unit weighs eight poundsand measures 3'/2 inches high. Itshalf -rack width allows the mul-timeter to be mounted in anystandard instrument rack-singleor two -across. It also is equippedwith a carrying handle and tiltstand for portability. An optionalbattery pack can be purchasedwhich allows approximately sixhours of continuous operation.The batteries are recharged by itsbuilt-in charger when operated byAC power. The battery packmounts inside of the multimeterpackage and includes a conveni-ent self -test feature for monitor-ing the battery condition.
The digital logic and readoutboard swings up to permit accessto components and solder connec-tions. Inter -connections are madethrough plug-in PC connectors.
For use outside of the shop themultimeter may be supplied withaccessories such as snap -off frontand rear covers and a carryingcase with storage compartment forprobes and cables. The price is$675.
TUNER SERVICECORPORATION SUBSTITUNER
Tuner Service Corporation hasrecently added the SUBSTITUN-ER to their growing field ofspecialized equipment.
The instrument has a brushedaluminum base with a flashanodized finish. The power supplyis transformer -powered with a fullwave rectifier circuit. The outputvoltage is regulated by a zenerdiode to provide good performancewhen operated with varying linevoltages.
Tuner Service Corporation's SUBSTITUNER. Formore information about this instrument circle104 on the Reader Service Card.
The unit employs both a detentVHF tuner along with a detentUHF tuner. The VHF tuner has apush to fine tune feature, withmemory allowing the operator togo from channel to channel with-out readjusting the fine tuning.The UHF tuner allows selection ofUHF channels in the same man-ner.
A manual gain control MGC)located on the front panel of theunit controls its gain. An addedfeature is a LED indicator locatedin the upper right hand corner ofits cabinet, whose intensity variesdepending on the adjustment ofthe MGC. As you increase or de-crease the gain, the intensity ofthe indicator varies proportion-ately.
Separate VHF and UHF inputsfacilitate the checking of home an-tenna systems. Separate VHFOUT, Channel 1 IN, and IF OUTconnections facilitate the check-ing of the TV set's tuner for agood/bad condition. A noted safetyfeature is a cover which enclosesthese connections at the rear oftheunit, which must be removed togain access to the phono-jacks.This prevents exposure to the highvoltage present on the phono plugswhen Substituner is connected tohot chassis TV set.
The Substituner comes com-plete with a three foot cable ter-minated within the extension in -line jack, which allows the use of ashort phono-jack cable or a phonoto clip lead cable for versatility.
The IF output frequency is cen-tered around 44 MHz, the stan-dard IF frequency. This allows theunit to be used for signal injectiontests in the majority of TV sets.
Removal of the back protectivecover, which is held in place by twoscrews, is necessary to gain accessto the UHF OUT and CHANNEL1 jacks.
The Substituner can be used tocheck the VHF tuner, UHF tuner,Channel 1 to VHF tuner and theAGC system.
In many cases the receptionmay be as good as, if not betterthan, the original tuner exceptwhere the bandpass is adverselyaffected by the coupling in the IFsection of the receiver. The price is$39.95.
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FULL 15 DAYS MONEYBACK GUARANTEE
SEE YOUR DISTRIBUTOR OR WRITE:
ELENCO ELECTRONICS INC.8144 W. North Ter., Niles, III. 60648312-564-0919 MODEL SO-
D My check or money order enclosed.
0 COD-Add $2.50 mailing & handling.
NAME
ADDRESS
0
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DISTRIBUTORS' INQUIRIES INVITED
...far more details circle 109 on Reader Service Card
JULY 1975, ELECTRONIC TECHNICIAN/DEALER / 43
TECHNICAL DIGEST
The material used in this section is selected frominformation supplied through the cooperation of therespective manufacturers or their agencies.
ADMIRALColor TV Chassis M10 - Scan Derived Power Supplies
This chassis employs three scan derived DC powersupplies: 33 volt, 24 volt and 235 volt. The 33 volt and 24volt supplies are protected by F1000, a 1.5 amp fuse.
Positive horizontal pulses from terminal 10 of theflyback transformer are coupled through F1000 to theanodes of D1000 and D1001. The pulse is rectified byD1000, filtered by C102B, C102C and R109, to become theB+ 33 volt supply. Diode D105 is used for protection whichdecouples any negative transient energy to ground. Thisprovides protection to the solid state components connectedto the 33 volt supply.
The same pulse is rectified by D1001 and filtered byC1000, producing a 35 volt supply which is dropped byIC1000 to become the B+ 24 volt supply. Diodes D1002 andD1003 act as protector diodes for transient protection in thesame manner as D105. Further filtering of the B+ 24 voltline is provided by C1001 and C1002. Integrated circuitIC1000, the B+ 24 volt regulator circuit, maintains thissupply at 24 volts during normal load variations.
The third scan derived supply is provided by the D100circuit. A positive horizontal pulse from terminal six of theflyback is coupled to D100 by R101. This supply is unique inthat the horizontal pulse is "stacked" on the B+ 120 voltsupply from the power supply board and therefore, only
Patent 3,778,713
The Wayne Model WT2A
!makes YOU moneyssaves much timemakes trouble-shooting easierA new concept in transistor testingbased on proven methods of circuitanalysis. A current limited AC volt-
age is applied to each semiconductorjunction under test. The resulting DC
voltage is monitored while the rec-tifying junction is passing normal
rated current. Abnormalities areeasily identified.
Indicates PNP or NPN Measures relative gain
Test leads applied without prior basing knowledge Locates base and collector during test
Indicates silicon or germanium Indicates transistor non -linearity
In -circuit tests with shunt impedancedown to THREE ohms
Performs all of above and more in less thanten seconds
WfkflELECTRONICS
5412 Nordling St./Houston. Texas 77022...for more details circle 129 on Reader Service Card
44 / ELECTRONIC TECHNICIAN/DEALER. JULY 1975
01111011.
SCAN DERIVEDDERIVED POWER SUPPLIES
(24.1 V 4.21110C4T 414,1)
requires a half - wave rectifier to achieve 235 volts of B+.The pulse at the D100 anode is rectified by the diode wherethe derived voltage is added to the B+ 120v referencesupply and becomes the B+ 235 volt source. Diode D104provides transient protection in the same manner as D105,D1002 and D1003. Filtering is provided by C102A, C102Dand R100.
All of the scan derived B+ supplies are dependent oncorrect operation of the power supply board. This is the casebecause the pulse amplitude in the flyback transformer(from which all three derive) is a function of the B+ 120 voltregulated supply as well as proper horizontal circuit opera-tion.
GENERAL ELECTRICColor TV Chassis MC-No Raster, But Sound Normal
If you encounter a no raster problem, but the sound isnormal, and resistor R1103 on the Buffer Module is over-heated or open, inspect the assembly and make the follow-ing changes: 1) Remove the high voltage assembly mount-ing screw and turn the assembly to view the back side.Check for a broken wire to capacitor C1702B (can typeelectrolytic). In early production the wire was stretchedtight and may have been broken in shipment. 2) Replace orredress the wire to provide slack, and resolder to C1702B.3) Replace Resistor R1103 (EP14X63) if overheated oropen. 4) If raster is not restored, check Q1702. If set wasleft on, it may have failed.
MAGNAVOXColor TV Chassis T985/986 - Vertical Jitter
Vertical jitter may occur on some of these portable colorTV chassis. When the amount of jitter varies as the bright-ness is changed, the problem is probably caused by a lowhigh voltage setting or high line voltage. Ensure that thehigh voltage is set to 22 kv for the T985 and 24 kv for theT986 (zero beam current). The condition can be furtherimproved by changing the value of R7 on the 120v regulatormodule. The resistor should be changed from 220 ohms to470 ohms.
A second condition of vertical jitter which is not as-sociated with brightness change may be corrected by add-ing a .1 mfd capacitor across R12 on the Vertical Oscillatormodule.
21 Detent Tuners - Replaceable UHF Pot Strips
The 21 detent tuner is a combination of VHF tuningstrips and UHF potentiometer strips. The UHF strips applyvoltage to a separate varactor UHF tuner. The PN for theUHF strips is 171356-1. If a UHF pot strip becomes defec-tive, it should be replaced in lieu of replacing the completetuner. IN
NEW PRODUCTS
UHF -TO -VHF CONVERTER 135
'the Blonder - Tongue Model UX - 3single - channel UHF - to - VHFcrystal - controlled converter will nowbe avant- hie with a 0.002 percent
crystal in place of the standard 0.005percent crystal. The new crystal,available at an extra charge of $45,improves stability and maintains FCCCATV rules tolerance specifications of25 KHz carrier frequency drift. Theconverter is a solid - state, low - noiseUHF to VHF converter in CATV andMATV systems. Each converter is de-signed for a specific conversion fromone UHF channel to one VHF channel.The circuitry eliminates the possibil-ity of deteriorating the UHF noise fig-ure with the indiscriminate use ofhigh - noise external amplifiers. Inweak - signal areas, a mast - mountedpreamplifier would be used to preservethe best signal - to - noise ratio. Inareas where signals are medium tostrong, the converter input comes di-rectly from the antenna. The unit hasa 75 - ohm input and two 75 - ohm"Loop - Thru" mixing outputs. Thisoutput feature permits low - loss mix-ing of non - adjacent VHF channelsinto head - end amplifiers.
OSCILLOSCOPE 136
A 10 MHz dual channel, generalpurpose portable oscilloscope Model1010A is introduced by BallantineLaboratories, Inc. This all solid - state
,G
instrument provides 5 mV/cm sen-sitibity in two identical input chan-nels over the full bandwidth of DC to10 MHz. In the dual channel display
mode switching from alternate tochopped sweeps is automatically ac-complished by the sweep range switchoperation. The amplitude and sweepranges are fully calibrated. The trig-ger system is flexibile, and provides abright baseline display in the absenceof an input signal. The 3.6 kv ac-celerating voltage on the 8 x 10 cmCRT provides bright easy to readtraces, even at the sweep rate of 100ms/cm. The trigger selection providesmodes optimizing video frame and linesync. Lissajous patterns are quicklyset up by switching into the X - Y modeof ope. .ation. The instrument weighs15 lbs and is priced at $495.
DIGITAL MULTIMETER 137
A portable Digital MultimeterModel IM -2202 is the lowest - priceddigital multimeter Heath has ever of-fered. Included in the unit are fourrechargeable nickel - cadmium bat-teries and a built - in charging circuit.Up to eight hours of continuous opera-tion can be obtained from each chargeor it can operated from 110 to 220 VAC
When necessary. Its 26 ranges includefull scale ranges of 100 mV to 1000volts DC, 100 mV to 750 volts AC, 100µA, to 1000 mA and 100 ohms to 1000kilohms. The 100 percent overrangecapability allows measurements up to1.999 on all ranges except 1000 VDCand 750 VAC, giving full 2 amp or 2megohm capability. Overrange condi-tion is automatically indicated by aflashing "1" display. If a lab standardis used for calibration, DC accuracy is+ 0.2 percent. For AC, accuracy with alab standard 0.2 percent. For AC, ac-curacy with a lab standard is + 0.5percent to 10 KHz. Internal standardssupplied with the kit allow easy fieldcalibration to + 0.5 percent for DC and+ 1 percent for AC. The large 3'/2 -digit display features automatic polar-ity indication and decimal pointplacement. A continuous - rotationrange switch and four pushbuttonfunction switches select any of themeasurement ranges. Price is$179.95.
FM SIGNAL GENERATOR 138
The Model 1012 FM SignalGenerator, introduced by Gaw Co.,Inc., is designed specifically to meetthe requirements of the mobile com-munications industry. It features digi-
Some storessell testequipmentat discountprices.At Fordhamwe discounttheir discountprices.B&K, EICO, RCA, SENCOREFLUKE, HICKOK and LEADER
Complete line of tubes,tools and electronic supplies
FREE CATALOG
FORDHAMRADIO SUPPLY CO., INC.
558 Morris Ave., Bronx, N.Y.Tel: (212) 585-0330
...for more details circle 113 on Reader Service Card
BRAND NEW FROM ENDECO
the solderingiron with alight r41:
i7.\Exclusive new safety lightshows when power is on
MODEL 540S $10.95 NET
Two heats -20w and 40w-to handle any job On -off switch Cool, unbreakable polycar-bonate handle Ironclad tips for longer life
Burn -resistant neoprene cord 81/2" long,
2 oz Converts to a desoldering iron withlow cost attachment Also desoldering ironsand soldering/desoldering kits.
See your distributor or write . .
ectdeCU
5127 EAST 65TH ST.
)enter ise
INDIANAPOLIS,INDIANA 46220PHONE 317/251.1231
corporation...for more details circle 110 on Reader Service Card
JULY 1975. ELECTRONIC TECHNICIAN DEALER 45
tal frequency read - out, eight fre-quency ranges, low frequency outputfor IF alignment, internal/externalmodulation - DC coupled, double -
trace sweep modulation, automaticoutput leveling, external counter tobeyond 20 MHz, electronic fine tuning,double shielding, spectral purity, andless than 100 Hz residual FM. The de-sign of the instrument offers the user afrequency source and a standard of RFvoltage and deviation. The spectralpurity of the unit, in combination withthe frequency counter, give the unitwide application.
FUSED POWER -TAP 139
A new product that greatly simp-lifies power connection for the instal-lation of auto radios, stereos, and otherelectrical appliances is introduced by3B&D Products, Inc. Called "Add - a
fuse," the device has prongs on oneside of an insulating board that snapinto an existing fuse clamp. On theopposite side of the board there are twofuse clamps. One receives the fuse forthe circuit in which Add - a - fuse isplugged, and the other picks up andfuses the hot side for power to the newinstallation. A piece of hookup wire isattached for connection to the ap-pliance. The arrangement makes bothcircuits independently fused.
SWEEP/FUNCTION GENERATOR 140
Dana Exact Electronics, Inc., an-nounces a low cost Sweep/FunctionGenerator with 50 ohm output. TheModel 196A offers sine, triangle,square, pulse, and sweep waveformsover a frequency range of 0.1 Hz to 1MHz. Signal amplitudes of 20 volts p -
p open circuit or 10 volts p - p into a 50ohm load are available. The instru-ment has an internal sweep generatorto sweep the frequency of the maingenerator with a variable sweep widthup to three decades (1000:1). Thesweep rate is adjustable from 1 msec to10 secs. Other features include DCoffset, variable ramp or pulse
waveform with inverting capability,square/pulse risetimes of less than 100nsec, and a separate 1 -TL compatibleoutput with less than 25 nsec risetime.Price $350.
CABLE SHEATH SLITTER 141
P.K. Neuses, Inc., introduced a cableslitter tool for slitting most any type oflarge or small cable jackets. The No.N-62267 slitter has a very sharp,tough hook blade which digs in bet-ween the sheathing and wires andwith the side supports, guarantees theuser an accurate jacket stripping. The
QQ III I^1 1 1 1 111 11111 1141 111 1 1 1 111 111 t 1111114 VIII 11111111111 I 111 1444 # Pig
RAYTHEON
Rapid RebateTake this ad to your participating Raytheon Distributor and receiveA Free Raytheon 6GH8A Receiving Tubewith your purchase of $15.00 or more (dealer cost) of Raytheon RE replacement semiconductors.
Raytheon RE-the only broad line of semiconductorsthat gives you all of these:
individual packaging with replacement cross references printed on the bag comprehensive coverage of both domestic and foreign types listings in Sam's Photofacts® a complete reference guide and catalog
Plus a Rapid RebateOffer expires October 15, 1975. Good at participating distributors, or send proof of purchase to:Raytheon Company, DPO, 4th Ave., Burlington MA 01803
OVOIVIVA151ItIII 111111111
ET -7
I I 1111111111111111111 111111111 11111111111111111111111111
...for more details circle 122 on Reader Service Card
46 / ELECTRONIC TECHNICIAN/DEALER, JULY 1975
razor sharp hook allows the user to cutinto cable at any point without anyprevious notching, thus avoidinghazard to the inside wires as well ashands. Two screws hold the blade incutting position and also secure anextra blade with the cutting end pro-tected until used. The forked ends ofthe slitter are ductile aluminum, andmay be carefully bent to fit endlesscable sizes. The tool is 6 inches by 11/2inches and weighs only two ounces.
CB SERVICE MONITOR 142
The Lampkin Model 109 CB ServiceMonitor measures and generates RFand audio frequencies, monitorssingle sideband, measures AM andFM modulation, generates CW andAM signals and serves as a digital fre-
quency counter with a range of 50 Hzto 30 MHz. The Model 109 is designedto easily accommodate future growthof CB. For example, if Band E is acti-vated, a 220-230 MHz band and FMdeviation feature can be quickly addedat a nominal cost. As the service shopgrows, up to six other 10 -MHz bands inaddition to CB can be added to allowservicing of marine, aviation, andbusiness frequencies through 512MHz. Other options allow the additionof a frequency error meter, sweep and12 volt DC operation. Other features
include: The ability to measure fre-quencies to accuracies of better than 1part per million; an eight -digit LEDfrequency display; capability of eight10 -MHz bands and measurement ofAM modulation (0-100 percent) andFM modulation (2 KHz and 6 KHzscales). The unit weighs 17 poundsand measures 634 inches high by 17inches wide by 11 inches deep. Basicprice is $1,550.
TRIPOD ROOF TOWER 143
A new 10 footTripod Roof Towerhas been developedby South River. Car-ton packed, thisheavy duty 10 foot,galvanized, rust -resistant, tower isshipped particallydisassembled. It canbe assembled in ashort time with noprevious assemblyexperience. The tow-er, Model HDT-100KD was designed for TV/FM/CBantennas that required un-guyed,roof -top installation. It incorporates aclimable ladder in its design for easein mounting the mast and antenna.This unit includes pitch patches forwatertight leakproof roof mounted in-stallation. Diagonal, torque -buttressing structural members con-tribute to the high strength, lowweight, special design of this unit.Weighing under 28 lbs., this unit hasbeen designed to come within the 108inch dimension limitation imposed byUPS on shipments. A 15 foot ModelHDT-150 tower is also available forUPS shipment within the same di-mensioned carton.0
New 21/2 digit Heathkit DMM-only $7995The new Heathkit IM -1212 Digital Multimeter is the DMM you've beenlooking for...it's easy to read, has built-in calibration standards, serv-ice bench styling, easy assembly...and it's low cost. Four overlappingAC and DC voltage and current ranges and five resistance rangesmake operation fast and easy. Accuracy is very good for a meter inthis price range: 1% on DC volts, 11/2% on AC volts and AC/DC cur-rent, and 2% on resistance. Full scale ranges are: DCV, 2, 20, 200,1000V; ACV, 2, 20, 200, 700V rms (25 Hz to 10 kHz); DC current, 2, 20,200, 2000 mA; AC current, 2, 20, 200, 2000 mA (25 Hz to 10 kHz);Resistance, 200, 2k, 20k, 200k, 2000k ohms. Lighted panel indicatorsshow overrange, positive and negative DC voltages and current. Allsolid-state design uses IC circuitry for clear, non -blinking display withreadout update every 16 msec. and automatic decimal positioning.Overload protected. 120/240 VAC. Also available assembled for only$125*.
See the complete line ofHeathkit instruments inyour FREE Heathkit catalog.
HEATH
SchlumbergerHeath Company,Dept. 24-07Benton Harbor, MI 49022
Please send my 'Tee 1975 Heathkit Catalog.
em
11161A. ORDER PRICES; F.0.. FACTORY.LN cEs a SPEC, iCrpONS SOW,' TO CHANGE WITHOUT 140/ICE.
ZIP
1
TE-326.
...for more details circle 114 on Reader Service Card
.:ULY 1975. ELECTRONIC TECHNICIAN/DEALER 47
CLASSIFIEDRATES. 35v per word. 450 per word Bold FaceType. Add $3.00 if you wish Box Number. Minimum$10.00 charge. Classified Display Rate billed$40.00 per inch, 1 inch minimum. Remittance mustaccompany order. Mail ad copy to: Roz Markhouse,ET/D, 757 3rd Ave., N.Y., N.Y. 10017.
Business Opportunities
OWN YOUR OWN PICTURETUBE REBUILDING BUSINESS
With Lakeside Industries rebuilding equipment you canrebuild any picture tube.
For complete details sendname address zip code toLAKESIDE INDUSTRIES3520 W Fullerton An.Chicago. III 60647Phone 312 342,3399
Improve sagging sales with high profit -quick turnover CB equipment. Write fordealer application. Wheeler -Dealer Elec-tronics, Dept. ET/D, Bascom, Florida32423.
For Sale
RADIO & T.V. TUBES - 36 cents each.Send for free Catalog. Cornell, 4215-17University, San Diego, Calif. 92105.
CANADIANS SAVE BIG MONEY!SURPLUS, CLEAROUTS AND BANK-RUPTCY INVENTORIES. HIFI ANDPARTS. CATALOGS $1.00. ETCO-DELECTRONICS. Box 741, MONTREALH3C 2V2.
HARD -TO -FIND TV & RADIO PARTSNEW AND USED. ASK ANYWAY CMC4329-4 WOODMAN, SHERMAN OAKS,CA. 91423
FOR SALE
Established Radio & TV Sales and servicein Sunny Arizona. Retiring. P.O. Box 236,Mesa, Arizona 85201
REBUILD PICTURE TUBES. We sell new& used equipment with complete instruc-tions in our plant. We buy used equipment.Factory Outlet, 951 E. Hudson St., Colum-bus, OH 43211 614-263-0645.
CHEMTRONICS CHEMICALS* WhalSoldering Irons and Heat Guns* Transis-tors, Diodes, Resistors, etc. For the tech-nician or the do it yourselfer. DistributorPrices. Send 25(t for catalogue Box 100ETD
TUBES receiving, factory boxed, lowprices, free price list. Transleteronic, Inc.1365 39th St., Brooklyn, N.Y. 11218A,Telephone; 212-633-2800.
FOR SALE -RIDERS MANUALS 23 Radio,21 TV, Vol 1 Sams Best offer lot over $7.50@ LYSTEMS, 106 Eddy, Dix Hills, NY11746
For Sale: Howard W. Sams Photofacts,complete set -folder #14041402. In fourfiling cabinets, complete price $1400.00.Valley TV & Appliance, 29465 ChualarCyn. Rd., Chualar, Calif. 93925.
TV & RADIO TUBES .36¢ EA!! Send forfree color parts catalog Your order free ifnot shipped in 24 hours. Cornell Elec-tronics 4215-17 University San DiegoCalifornia 92105
UNUSUAL SURPLUS, CLOSEOUTSAND PARTS CATALOG. RUSH $1ETCO-4 ELECTRONICS. Box 741,MONTREAL H3C2V2.
BURGLAR alarm police dialing unit au-tomatically calls police or any number.$29.95. Easy to program and easy to in-stall. Free literature. S&S Systems, Box12375 E, North Kansas City, Mo. 64116
For Sale: Used picture tube rebuildingequipment, complete -and equipment forlaminating and delaminating face plates,and supplies. Escom Pack Sr., PaverBarnes Road, Marysville, Ohio 43040 (513)642-7161
L
send a message......write here.
1. Number of insertions: (circle) 1 2 3 6 122. Start with (month) issue (Copy must be in by 1st of month preceding)3. Amount enclosed: $PAYMENT MUST ACCOMPANY ORDER WE'LL BILL RATED FIRMS NO AGENCY COMMISSION
NAME COMPANY
STREET
CITY STATE ZIP
MAIL COPY FOR AD(S) TO: ROZ MARKHOUSE, Electronic Technician/Dealer, 757 Third Ave., New York, N.Y. 10017
RATES: 35v per word; 45v per word Bold Face Type. Add $3.00 if you wish Box Number.Minimum $10.00 charge. Classified Display Rate billed $40.00 per inch, 1 inchminimum.
ELECTRONICTECHNICIAN/DEALER CLASSIFIED
48 / ELECTRONIC TECHNICIAN/DEALER, JULY 1975
Construction PlansConstruction Plans Repair your own TV. Valuable Information
$2.00. TIP$ Bruce, Miss. 38915.
DIGITAL CIRCUIT plans are availablefor; Automatic 125 Meg. freq. counter withmany features, Delux Logic Probe withpulse indicator, Digital Clock 6 digit read-out, 60 Hz. time base for all digital clocks;Digital tachometer. Plans $2.50 each,Boards available for all plans, drilled,etched and plated, Com-Tronics, 144Cloverside Ct., Buffalo, N.Y. 14224. 7/75
YOU'REWHISTLINGIN THEDARK,,,
cirZI J44
IF YOUTHINKHEART ATTACKAND STROKEHIT ONLY THEOTHER FELLOWSFAMILY.
Help yourHeart...Help yourHeart Fund J)
n. .h, PsNuFn
Complete Construction Plans - TELE-PHONE: Answering Device, AutomaticDialer, "Black Boxes," Call Diverter, CallLimiter, Conference Bridge, Central DialExchange, Melodic Ringing, Recorder -Actuator, Remote Control, Schematics,Speakerphone, Telelink Burglar Alarm,Voice Schrambler, $3.00 each. ELEC-TRONIC: Biofeedback Conditioner, Hor-ticulture Stimulator, Multifrequency En-coder Network (Speeds telephone calling100%!). $5.00 each. ONE YEAR SUB-SCRIPTION to Telephone Electronics Line(TEL) $6.00. "The Legal Aspects of Inter-connection" book, $29.95. All of the con-struction plans above plus a one year sub-scription to TEL $29.95. TELETRONICSCOMPANY OF AMERICA, 22035 Bur-bank Blvd., Suite 122, Woodland Hills,Calif. 91364.
WHY BUY A CRT RESTORER? If youhave a B&K 465 or 466 rejuvenator, con-vert it to a CRT Restorer. For informationJames R. Chancellor, 1708 Edgerly Av-enue, Albany, GA 31707
COMPLETEComoraucnom NAM
TELEPHONE PLANS. SI mesa.kmoenm Drain. Amoomite Dialer. "Illnel Roe". 1.1111 %eerier. Call broodlooleteete Bridge. Control Nal Exchange. Melodic Losing Generator.Recorder Arius, Rearm Control. Sebeinaties, Spealtrabone. Tekliu1Burglar Maim. fence krambkr. Dial/Tom Comm, Tom/Dial Convener
NISI.. PLANS: SA .n eadiBiofeedback Ismlitioort. Alshirfresoemy Encoder Seined. 110fIN1111tt
Stuadator. Dodecahedron Smoker Eatleasme. Photograpluc Pinhole Camera
ALL OF THIPPPPp FRICTION PLANS ABOVE, S14.g5 ASSAILED.
s" LEARN THE SECRETS tia
'IS OF YOUR TELEPHONEloom Eltdrillaks
der ftodeted I.,. bellied that [tiepin. dial, Nee diti cankm, the trick. On idealism oak Get the inside oar, of idealismsee.,- tiro said. nod flan, and remain up to date vital femme,soils lie telephone missed TELEPHONE ELECTRONICS LINEnoil.cation demeord lot Om telephone e.Ilnv Moor Piteek. and
dmrinevid ..maiming 'toddling article, shich eller a sealti ofInd .nintrnat...n Technical them, n ale diAcmaed, dam, the [album ado,
Current News Items Code NumbersIllustrations Games Facts PlansProjects History Comics StoriesFacts prieviously Tel. Co. confiden-
tial is now published in TELLOm year mined/tin ram Anted Staid Soo. Comdian A foreign Soo
ALL OF THE CONSTILI T ION PI ANA ABOVE PUS A ONE TEAR SLI-M RIPTION TO TEUPHOAt F I II I Roma UNE, 329.9% AIRMAILED.
TIE LEGAL REMOTEAF IIIITERCOMMECT1ON
V. 11 RS Fillip
The complete reference book to yourLEGAL RIGHTS as a telephone sub-scriber. Study toll evasion, tariffs,wiretapping, customer provided equip-
ment, and many more!AIL Of THE CONSTRICTION PUNS 1501E AND A 11.11141 SEBSCRIPTIONTO TEL PU S "THE LEGAL ASPECTS Of lATFRLONSII SAO. ASSAILED.
TCRTELETRONICSCOMPANY AJVIERICAe2035 BURBANK BLVD.,WOODLAND HILLS CA 91364 US%
Educational Courses
REPAIR TV TUNERS -High Earnings;Complete Course Details, 12 Repair Tricks,Many Plans, Two Lessons, all for $2. Re-fundable. Frank Bocek, Box 3236, Ent.,Redding, CA 96001.
EDUCATIONUNDERSTAND digital electronics-calculators, microprocessors, clocks. Newprogrammed learning courses. Design ofDigital Systems, 6 volumes, only $14.90.Digital Computer Logic, 4 volumes, $9.90.Both $19.90. Unconditional refund if dis-satisfied. CAMBRIDGE LEARNING EN-TERPRISES, Box 428, FDR Station, NewYork, NY 10022
BUILD THAT ELECTRONIC ORGANYOU ALWAYS WANTED AT A PRICEYOU CAN AFFORD. Third edition of "Or-gan Builder's Guide" pictured product kitline, circuits, block diagrams, designrationale using IC divider and independentgenerators with diode keying. $3.00 post-paid. Also, free brochure on keyboards.DEVTRONIX ORGAN PRODUCTS, Dept.A., 5872 Amapola Dr., San Jose, CA. 95129
How to save money on tuner repairs. In-formation $2.00 TIP$ Bruce, Miss. 38915
Manuals and Periodicals
HEAR POLICE/FIRE Dispatchers! Cata-log shows exclusive official directories of"Confidential" channels, Send self-addressed stamped envelope. Dealerswanted. Communications, Box 56 -ET,Commack, NY 11725
NEW CANADIAN MAGAZINE. "ELEC-TRONICS WORKSHOP". $5.00 YEARLY.SAMPLE ETCO-C, Box 741MONTREAL H3C2V2.
Wanted
WANTED: PICTURE TUBE REBUILD-ING EQUIPMENT used or new..Call orwrite Atoll TV, 6425 W. Irving Park,Chicago, Illinois 60634. (312) 545-6667.Evenings until 11 PM call (312) 235-0420
Want Schematic for Korvettes TV set XAMModel 1269 and need part number for yokeand horiz. trans. Arthur R. Vickery, TheMusic Shop, 548 Main St., Torrington,Conn. 06790.
ELECTRONIC
TECHNICIAN/DEALERis not responsible forany of the items,plans, courses orquality of productsoffered through ourclassified section.
JULY 1975, ELECTRONIC TECHNICIAN/DEALER / 49
DIGITAL
PERFORMANCE
YOU CAN
RELY ON.
The Hickok Model 334 DMM isa rugged, non -temperamental,hardworking tool that's easy touse and easy on your eyes.Hickok has established a uniquereputation in digital electronicsduring the past 10 years. TheModel 334 is another exampleof our engineering expertise -an economical lab qualityinstrument with exceptionaldurability and accuracy. Easy reading, green
fluorescent display 31/2 digit - auto polarity 26 ranges including 200 mV
AC & DC ranges Fast response -
2.5 readings/sec
Basic Accuracies (% of reading)DC Volts; ±0.2% (±0.5% on 200V,
1200V ranges)AC Volts; ±0.5% (±2.0% on
200 mV, 2V ranges)OHMS; ±0.5%DC Current; ±1.5%AC Current; ±2.0%
Ask to see the Model 334 at yourHickok distributor. It's a nocompromise DMM at a priceyou can afford.
$22900
HICKOKthe value innovatorINSTRUMENTATION & CONTROLS DIVISIONTHE HICKOK ELECTRICAL INSTRUMENT CO.10514 Dupont Avenue Cleveland. Ohio 44108(216) 541-8060 TWX: 810-421-8286
...for more details circle 115 on Reader Service Card50 / ELECTRONIC TECHNICIAN/DEALER. JULY 1975
READER
SERVICE INDEX
ADVERTISER'S INDEX
131 AMP Special Industries 50
132 Astatic Corp. 39
105 Blonder -Tongue Laboratories ..8
106 EICO Electronic Instruments
Co 4
107 Electronic Book Club 16-19
108 Electronic Devices 50
109 Elenco Electronics 43
110 Enterprise Development
Corp. 45
111 Fluke Manufacturing, John 33
112 Fluke Manufacturing, John 33
133 Ford Motor Co 26-27
113 Fordham Radio Supply Co. ...45
GTE Sylvania, Consumer
Renewal
General Electric Co., Tube
Div. 23, 32
114 Heath Co, The 47
134 Hewlett Packard 38
115 Hickok Electrical Instrument
Co. 50
116 Leader Instruments Corp. 6
117 Mountain West Alarm
Supply Co. 50
118 Oelrich Publications 50
119 PTS Electronics Cover 2
Quasar Electronics Corp 31
120 Quietrole Co. 4
121 RCA Solid State 5
122 Raytheon Co., Receiving
Tubes 46
123 Simpson Electric Co 3
124 Sprague Products Co. 7
125 T & T Sales Co 42
126 Tech Spray 41
127 Triplett Corp. Cover 4
128 Tuner Service Corp 11
129 Wayne Electronics 44
130 Weller-Xcelite Electronics
Div. Cover 3
FREE FREEto introduce you to
SOLID STATE
REPLACEMENT
RECTIFIER rijiTUBES
Solid state rectifier tube replacementsoffer many servicing and profit advan-tages: 6 Solid -Tube Ca types replaceup to 37 different high voltagevacuum tubes. They're somethingyour customers will appreciate.
' Eliminates need to replace defectivefilament winding on flyback. NoX-radiation. Reduces fire hazards. No filaments to fail. Reliable. Solidstate. Faster warm-up for picture. Modernizes older sets. Much higherprofit than vacuum tubes.
Get the full story on EDI Solid -Tubes', rectifiers, and get a freeSilicon Focus Rectifier too, just byasking -on your letterhead or businesscard, please.
Am ELECTRONICDEVICES, INC.
21 Gray Oaks Ave.,jYonkers, N.Y. 10710Telephone 914-965-4400
...tor more details circle 108 on Reader Service Card
0011111 UY AMPCABLE TIES
BY MAIL!Up to twice as strong. Self-locking.Nylon with dual stainless -steel pawls.Four sizes. Various colors. Send $1.00for generous trial package 25 ties.
We'll include new AMP mail-ordercatalog free. Describes hundreds ofelectrical items for servicemen. Orderfrom: Ties, Dept. 3006,
AMP Special Industries,Valley Forge, PA 19482.
AMP Offer expires
SPECIAL Sept. 1, 1975
INDUSTRIESD,vision of AMP Products Corporation Valley Forge. Pa
.. for more details circle 131 on Reader Service Card
IT'S NO PUZZLETO ORDER
OELRICH SERVICE FORMSFOR TV.I1A010 8 2 WAY RADIO SERVICE LEGAL FORMS FOR CALIF. FLA.UTAH NOW AT YOUR PARTS JOBBER OR WRITE FOR CATALOG AM
OELRICH PUBLICATIONS4040 N NASHVILLE AVE CHICAGO. ILLINOIS 00634...for more details circle 1111 on Reader Service Card
FREE ALARM CATALOGHuge selection of burglar & fire sys-tems. supplies. Motion detectors, in-frared beams: controls, door switches,bells, sirens. 500 items, 99 pp. packedwith technical details. notes.
(Outside U.S.. send $1.00.10 mountain west alarm4215 n. 16th st., phoenix, az. 85016
...for more details circle 117 on Reader Service Card
@ PO, at produttoo
ELECTRONICTECHNICIAN/DEALER
17-#=-6COMPLETE MANUFACTURERS' CIRCUIT DIAGRAMSAND TECHNICAL INFORMATION FOR 5 NEW SETS
ADMIRALColor TV Chassis 4M10
ADMIRALTV Chassis TL6
MAGNAVOX 1595Color TV Chassis T995
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R333 - 100K, brdeness Control 75A1-212R339 - 400 ohm AGC delay 75A101-35L201 - cod. 4.5MHz 72A317-1L301 - coil. 47 2SPAH2 trap 72A415-8L306 - coil, det. 72A316-8L310 - coil, 4.5MHz. trap 72A317-9L501 - coil. honz. lock 94A480-1T201 - xformer, audio output 79A172-1T401 - yoke deflect T2L6 94A372-3T401 - yoke deflect T3L6 93A372-4T501 - xformer, honz. drive 72A417-1T503 - xformer, honz. output 79A166-4R203 - 25K, vol control w/Sw 75A1-225R326 - 500 ohm, contrast control 75A1-211R333 - 100K, bnteness control 75A1-212R339 - 4000, AGC delay 75A101-35R411 - 2 M, vert size 75A101-61R407 - 1.2 M. vent hold 75A191-3F601 - fuse, 1.5a 84A7-15
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COPYRIGHT 1975 BY ELECTRONIC TECHNICIAN/DEALER 1 EAST FIRST STREET, DULUTH, MINNESOTA 55802
SYMBOL DESCRIPTION ADMIRAL PART NO.
JT
502
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F1000 - fuse 1.5 amp 84A4-7L900 - line choke 73A31-23R153A,B - 250K, dual tint control 75A195-21R154A,B - 5K, dual color control 75A195-20R155A,B - 10K, dual brite control 75A195-17R156A,B - 5K, dual contrast control 75A195-20R630 - 200K, vert size 75A101-28R631 - 60K, vert hold 75A191-2R634 - thermistor 61A41-9R741 - 20K, brite limit 75A101-47R901 - 22K, B+ 120V, adj 75A199-31800 - coil osc adj 94A351-3
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SAFETY NOTICETHE ENSIGN Of THIS RECEIVER CONTAMS MANY
CMCKTS AIM COMPONENTS INCLUOE0 SPECIF1
CALLY PON SAFETY PURPOSES. 105 CONTINUO
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COPYRIGHT 1975 BY ELECTRONIC TECHNICIAN/DEALER 1 EAST FIRST STREET. DULUTH, MINNESOTA 55802
1595WARNING
MAGNAVOXColor TVChassis T995
120 VAC60 HZ
JULY 1975
J2
TO GROUND.
TO TUNER24V INPUT "I
TO TUNER ACC
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I1 7
2
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ELEcT,...0472197 r-1,=7.4^13irCOMPLETE MANUFACTURERS' CIRCUIT DIAGRAMSAND TECHNICAL INFORMATION FOR 5 NEW SETS
P2
TPI AFT
6.2V1
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6.2171 2
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TONE'rRI5000 1,-,
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Magnavox Consumer Electronics Company is committed tomarketing safe products which meet or exceed applicablesafety standards of industry, government agencies and in-dependent laboratories. It therefore uses parts in its productsdesigned for maximum safety, reliability and performance.
For continued safety of this product, parts shown in theshaded areas of this schematic must be replaced with onlythose identified in the Parts List of this manual. Use ofsubstitute replacement parts which do not have the same'safety characteristics as specified, may create shock, fire or;other hazards.
For maximum reliability and performance, an other partsmust be replaced by those having identical specifications.
Under no circumstances may the original design be modified.or altered without permission from The Magnavox Company,otherwise the consumer may be exposed to fire and/or shockhazards.
TOVIDEOMATIC
SW(PIN
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COPYRIGHT 1975 BY ELECTRONIC TECHNICIAN/DEALER 1 EAST FIRST STREET. DULUTH, MINNESOTA 55802
793e
TP40
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703653
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T995 Signal Flow Block Diagram
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COPYRIGHT 1975 BY ELECTRONIC TECHNICIAN/DEALER 1 EAST FIRST STREET. DULUTH. MINNESOTA 55802
1596PANASONICColor TV ModelCT -324
JULY 1975
CR
C'J 6
0
L11
A -A
ELECTRONIC 7 /-1,7z7-Li_qjdna xic
COMPLETE MANUFACTURERS' CIRCUIT DIAGRAMSAND TECHNICAL INFORMATION FOR 5 NEW SETS
UHF TUNER TNK36100EA
TR,KR 25C 2 1 5
28C611425[2116
VHF TUNER TNT0624KFE
- zl 110 IF CM-0 0-
13
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26360 11210 254245261144
0103. T104. TIOS. 1104 T151.1201.0202.
0903, T404.1902. T903 3106.
NOTICE1 RESISTORA1I 44. 1 *IV. 515
55.4 MaI.A1 CNN 11 R-1000 111.1 0.090
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COPYRIGHT 1975 BY ELECTRONIC TECHNICIAN/DEALER 1 EAST FIRST STREET. DULUTH. MINNESOTA 55802
UHF TUNER PARTS
C 130VB 7.6VE 7.2V
iht
6Vp p
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1.6Vp-p
3
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C 130VB 7.3VE 7.1V
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m
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L354
R364
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TTTR351
- R362 -L 351
R35IL 352
3 32V 12 190V4 570V 13 520V5 600V 14 6.3V (AC)
[6 30V
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28
SYMBOL DESCRIPTION
R118 - sound reject 500 ohm B EVLR6BAOOB52R182 - delayed AGC 5K B EVTVOUOOMB53R903 - AFT adj. 50K 8 EVLR6BAOOB54R820 - fuse resist 68 ohm + 5% ER012HJ680R450 - sub Vertical -hold 50K B EVTS3BAO0B54R465 - height 200K B EVIJOUS15825R468 - sub Vertical-lin 2K B EVTS3BAOOB23R469 - Vertical - lin, 200K B EVTJOUS151325R479 - Vertical -balance 1K B EVTS313A001313R614 - ACC 10K B EV753811001314
PANASONIC PART NO. R817 - B+ adj. 1K B EVTS3BAOOB13R610 - kill 10 K B EVTJOUS15B14L502 - choke coil TLP408T505 - flyback )(former TLF6404SFt - fuseR220 - sound control 50K LR259 sound control 50K L EVA85A06A54LR380 - bana-brite 100K B EVX59AF25550R381 - 2ohm CR386 - sub contrast control EVV58AF25C53
5K CR387 - sharpness control 5K C EVV85AF25C53
TSF35503PANASONICColor TV ModelCT -324
Ref. No. i Part No. Description Ref. No. Part No. Description
UHF TUNER (TNK36108EA) PARTS 0 D M01-0007-00 Indicator Shaft DM -01A
A Indicator Ass'y DM -01B 16 DM01-0015-00 Pinion Gear DM -01B
t DM01-0051-00 Supporter DM -01A lit DM01-0006-00 Indicator Gear DM -01A
0 DM01-0074-00 Indicator Drum DM -01D @ DM05-0002-00 Shaft Assembly DM -01B
® DM01-0073-00 Indicator Drum DM -01C 14 N8-827-07 Stopper 07
® DM01-0044-00 Indicator Spring DM -01A '20 DM01-0017-00 Stopper DM -01B
DM05-0005-00 Indicator Bracket Assembly CM -016 21 DM01-0018-00 Stopper DM -01C
6 DM01-0046-00 Geneva Stop DM -01A 21 DM05-0013-00 Double Gear Assembly
7 DM01-0070-00 Idle Gear DM -01C 21 N15-812-11 Screws
8 DM01-0071-00 Hub Gear DM -01C 21 N9-814-02 Double Gear Spring 02
:9.7 N15-812-11 Screw 24 DM01-0002-00 Housing DM -01B
10 DM01-0071-00 Hub Gear DM -02C 24 UY01-0047-00 Inner Cover UY-01A
L N17-818-04 E -Ring 8 UY01-0026-00 Cover UY-01A
g DM01-0069-00 Idle Gear DM -02B # UY01-0027-00 Cover Spring UY-01A
13 DM01-0045-00 Indicator Spring DM -018 t0 N7-811-03 Ball 03
B Complete Tunern (3.0 DM01-0062-00 Detent Spring DM -03A
14 DM01-0001-00 Housing DM -01A t DM01-0063-00 Spring Retainer DM -01A
CONVERGENCE ALIGNMENT
Convergence board of CT -324 is different from that of CT -914. Proceed with the steps as shown
R
TILT-RG
RG-DIFF
RG-AMP. LEFT
RG-AMP
R. StaticMagnet
B. LateralMagnet B. Static
Magnet
B -AMP
G. StaticMagnet
TILT -B
B -AMP. LEFT
B -AMP. RIGHT
RG-AMP. RIGHT
COPYRIGHT 1975 BY ELECTRONIC TECHNICIAN/DEALER 1 EAST FIRST STREET. DULUTH. MINNESOTA 55802
1597TRAV-LERTV ChassisTR2- 1 A/2A
ELECTRONIC E77=Fiza 36TECHNICIAN/DEAIER
JULY 1975COMPLETE MANUFACTURERS' CIRCUIT DIAGRAMSAND TECHNICAL INFORMATION FOR 5 NEW SETS
MODEL CHART
MODEL COLOR TUNER CHASSIS
T9P800T9P802T9P803T9P805T9P827
BlackWhite/RedWhite/GoldWhite/AvocadoBlack/Walnut
94A363-6 VHF94A361-3 UHF
TR2-1A
T9P800MT9P802MT9P803MT9P805MT9P827M
BlackWhite/RedWhite/GoldWhite/AvocadoBlack/Walnut
94A281-15 VHF94A296-4 UHF
TR2-2A
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1.1034
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COPYRIGHT 1975 BY ELECTRONIC TECHNICIAN/DEALER I EAST FIRST STREET, DULUTH, MINNESOTA 55502
no stringsattached
NEW Weller®CORDLESS SOLDERING IRONGOES ANYWHERE
A professional quality tool, Weller's feather -light andfingertip -handy WC -100 Cordless Soldering Iron allowsyou to make connections anywhere...withoutdependence on an AC cord and outlet.
The heart of the WC -100 is its high-energy,long -life, nickel -cadmium battery which springsinto action at the touch of your finger, heatingthe tip to over 700°F in just 6 seconds.And no danger of accidental discharge.Weller's exclusive sliding safety switchbreaks the circuit when your finger isremoved, won't lock in "on" position, anddoes lock in "off" position for addedsafety while restoring energy with fast -
power recharger (UL listed).Loosen two slotted set screws and
you've got instant choice of four tips...regular, long -reach, fine -point, or miniature...each mounted on an extra -strongstainless tube to resist bending. Tip iscontinuously illuminated by the built-in lightwhich focuses on the work area, a specialadvantage under poor lighting conditions.
Try this for size! It's a full-scale photo of thecompact WC -100. And the real thing is waitingfor you at your dealer or distributor...right now.Need to know more? Request literature.
41COOPERINDUSTRIES
Weller -Xcelite Electronics DivisionThe Cooper GroupP. 0. BOX 728, APEX, NORTH CAROLINA 27502
...for more details circle 130 on Reader Service Card
The reader that canstayon, and on, andon.The 603.The price Jf the Model 603V -O -M is only $173.
The one V -O -M you can forget aboutforgetting to turn off. The incredibleModel FET V -O -M withexclusive Triplett Micro-PowerTMdraws only 10 uA, can stay onindefinitely without impairing per-formance. Ideal wherever frequenttest changes, interruptions, distrac-tions-or gremlins-keep your V -O -Mworking when you're not.
Truly outstanding features:1. Exclusive Triplett Micro -
Power (TMPTm) providesbattery life in excess of a yearfor carbon batteries with unitleft or continuously 24 -hoursa day.
2. Low -Power Ohms (LP,JT^^)-6range:, with 70 mV powersource for in -circuit measure-ments without damage tocornp-ments.
3. FET V -O -M with PatentedAuto -Polarity --convenientand time -saving, always readsup scale.
Accurately measures electric andelectronic circuits on productionlines, in quality testing, during main-tenance, in service shops and oncalls, in the laboratory or classroom,in the field.
One range selector switch operatesthe unit. One probe handles allfunctions-AC, DC, MA, Ohms-anda simplified scale utilizes only 4 arcsfor all 44 ranges. The Low PowerOhm circuii permits fast circuitmeasurements without biasing semi-conductor device junctions. The
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Model 603 also has a unique,Patented Auto -Polarity circuit: pusha button, measure either plus or minusvoltages without switching leads.Make very fast voltage checks wherepolarity is known or doesn't matter.
See for yourself. Try the 603. Haveyour Triplett distributor or salesrepresentative give you a free
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demonstration of the tester that canstay on indefinitely without impairingits testing performance. You'll beglad you did. Triplett Corporation,Bluffton, Ohio 45817.
111111.TRIPLETTALL YOU'LL EVER NEED IN V -O -M's.
Triplett. The easy readers....tor more details circle 127 on Reader Service Card