ATOM!' RADIO TELEVISION At...and will stand up under the high temperatures, high ripple currents and high voltage surges encountered in TV equipment. Every Sprague TV capacitor rated

RADIO TELEVISIONAt

WILLIAM F. BOYCEPublisher

VICTOR M. TURNERArt and Sales

JOSEPH 1. ROCHEEditor

MORTON SCHERAGAContributing Editor

ISIDOR I. GROSSAssociate Editor

FRANK VAN SEETERSCirculation Manager

Volume 6 January 1950 Number 1

CONTENTSBlock Diagram in TV Troubleshooting Cyrus Glickstein 10

Properly used, the block diagram is one of the mostefficient tools in television maintenance. This articletells how to use it to best advantage.

New Twin Driven Yagi 12

Details about an entirely new television antenna whichhas proven its worth in fringe areas.

How to Construct the 1950 Modern Service Bench 14

Complete instructions for building a bench equipped tohandle radio and television service work efficien+ly.

Flywheel Sync Circuits Morton G. Scheraga 20

G -E has introduced improved fly -wheel sync in its latestreceivers. They are discussed in this article.

Rectangular Picture Tube 22

A preview of what we may expect in the not too distantfuture.

New Sweep Signal Generator Harry R. Ashley 24

Just placed on the market, this new instrument hasseveral features of interest to the service technician.

Perpetual Inventory System Betty Lee Gough 26

Want to set up an inventory system which is simple yetaccurate? This article will tell you how.

Electronically Speaking 5

How's Business 6

Radio Industry Newsletter 9

The Industry Presents 28

Trade Literature 30

Merchandising Corner 32

The Notebook 36

ADVERTISING REPRESENTATIVES

MidwesternStuart J. Osten

333 No. Michigan Ave.Chicago I, Ill.Dearborn 2-3507

Copyright 1950, Boland & Boyce, Inc.Radio and Television Maintenance is published monthly by Boland & Boyce, Inc., at 34 No.Crystal St., East Stroudsburg, Pa., U.S.A.; Executive and Editorial Office, 460 BloomfieldAve., Montclair, N. J. Subscription Rates. In U. S., Mexico, South and Central America,and U. S. possessions, $1.00 for one year, single copies 10c; in Canada $3.50 for 1 year,$6.00 for 2 years, single copies 30 cents; in British Empire, $4.00 for 1 year, $7.00 for 2years, single copies 45 cents; all other foreign countries, $5.00 for 1 year.

Entered as second class matter January 1, 1950, at Post Office, East Stroudsburg, Pa.,under the Act of March 3, 1879.

Change of address: Four weeks' notice required for change of address. When ordering achange, please furnish an address stencil impression from a recent issue if you can. Addresschanges cannot be made without the old stencil as well as the new one.

ATOM!'

WIST-

aeltV

SPRAGUE

TVdry electrolytic

is processed

FOR

I r(85° C.)

gigSprague leads again with

the largest, most completeline of replacement elec-trolytic capacitors for tele-vision receivers. Each typeis engineered especially fortough video applicationsand will stand up under thehigh temperatures, highripple currents and highvoltage surges encounteredin TV equipment. EverySprague TV capacitor ratedat 450 d -c working voltageor less has been processed for185°F. (85°C.) operation.Send postcard for specialTV Bulletin.

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RADIO AND TELEVISION MAINTENANCE JANUARY 1950 3

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4 JANUARY 1950 RADIO AND TELEVISION MAINTENANCE

RADIOI NDUSTRYRADIOINDUSTRYRADIOINDUSTRY

RADIO INDUSTRYEdited by Joseph J. Roche

NEWSLETTER

THE NEW YEAR- The end of 1949 found the industry in a healthier positionthan ever before. TV receiver production was soaring to all time highs, andteleset sales were at record levels. All this meant good prospects in 1950 for

the service technician. If current predictions of a 3,000,000 plus teleset out-put in 1950 come true, he will be busier than he has ever been before.

FCC CALENDAR- The color situation was as indefinite as ever. The dem-onstration of the Color Television Inc. (CTI) system was postponed to thelatter part of February, and the second comparison showing of the varioussystems proposed to date (CBS, RCA, and CTI) was to follow shortly there-after. In the meantime, however, other organizations continued to announcetheir own developments. DuMont let i: be known that it was evolving adevice of its own, and the Rensselaer Polytechnic Institute released the infor-mation that two of its scienists had developed a color system fully compatiblewith today's black -and -white TV. Finally, Optiko Teletube Corp. claimed ithad a new process for color television, using present-day receivers, and atransmission tube which will permit transmission of the entire color spectrum,using present TV channels. In addition, FCC instructed CBS and RCA to dis-tribute a number of colorvision sets among various portions of the populationin order to get their reaction. All in all, it looks as though the final decision oncolorvideo won't be reached for some time.

The Commission had two other items on its TV agenda: Phonovision anda new frequency allocation. Phonovision, Zenith'sfilms and other news events are sent via telephone lines to the properlyequipped telesets of paying subscribers, will get its hearing in the middle ofJanuary. Sessions on the new television frequency allocation are scheduledfor the end of February.

FOR SERVICES RENDERED- John F. Rider, president of the publishing firmbearing his name, has received another award from a servicemen's associa-tion. The latest one was presented to him by the Empire State Federation ofElectronic Technicians Associations (ESFETA) "for his inspiring and pioneeringeducational efforts". The award, a bronze plaque, was made recently at anESFETA banquet. Mr. Rider has been extremely active on behalf of theservice technician, and was instrumental in inaugurating the current ESFETATV lecture series (whose opening talk he delivered).

TOWN MEETINGS- During the recent meeting of the Radio ManufacturersAssociation (RMA), plans were submitted for a continuation of the "TownMeetings" program. Mr. Sprague, of Sprague Electric Co., and chairman ofthe Town Meeting Committee of RMA, was authorized to get together withteleset manufacturers and discuss with them a proposal to hold Town Meetingsin 60 television areas. The meetings would be conducted by manufacturersand distributors through voluntary subscriptions. The plan includes the prep-aration of slide films which will summarize the topics which have been dis-cussed at the seven previous RMA Town Meetings.

TELEVISION COMMITTEE-RMA has instructed its Television Committee topresent to the FCC a plan for the immediate establishment of an industry -wideNational Television System Committee to be composed of top engineers inthe field of television and electronics and to (1) present technical data relativeto allocation of the u -h -f frequencies and the lifting of the freeze on v -h -f alloca-tions and (2) to recommend basic standards for the future development ofcolor television. In 1941 a similar Television System Committee drafted andrecommended to the FCC standards for present black -and -white televisionbroadcasting.

RADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRY'RADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRY.RADIOINDUSTRYIRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYIRADIOINDUSTRYIRADIOINDUSTRY,RADIOINDUSTRY'RADIOINDUSTRY,RADIOINDUSTRY!RADIOINDUSTRY,RADIOINDUSTRYIRADIOINDUSTRYRADIOINDUSTRY,RADIOINDUSTRYIRADIOINDUSTRY1RADIOINDUSTRYIRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRY,RADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRADIOINDUSTRYRAninINDUSTRV

AS outlined in the preceding arti-cle, troubleshooting a teleset is

best accomplished by following thesethree steps:

1. Locating the defective section.2. Finding the defective stage.3. Isolating the faulty component.It was pointed out that for all of

these steps the technician has achoice of several tools to expedite histroubleshooting.

In this and the following article,we will discuss the first step only-the various methods which the tech-nician can employ to locate the de-fective section. These methods con-sist chiefly of three operations whichgenerally take no more than a fewminutes:

1. Analyzing of the sound and pic-ture information coming over theTV receiver being serviced.

2. Applying this information tothe block diagram of the set, in orderto decide which section is causing thetrouble.

3. Checking the appropriate con-trols to make sure that a fault reallyhas developed in the receiver, andthat the defect is not due to an in-correct setting of a control. It isoften necessary to check on everychannel instead of on only iftrouble appears in either sight orsound, before making a definite de-cision concerning the faulty section.

In transformerless sets, there isone extra step, which will be dis-cussed later.

The Block Diagram

As can be readily seen, using theblock diagram is the most importantstep in locating the defective section.

Service

Techniquesave more time by using the

BLOCKDIAGRAM

IN TV TROUBLESHOOTING

by Cyrus Glickstein Let the block diagram be your roadmap

American Radio Institute to find your way around in a teleset

One of the more popular types ofelectro-magnetic receivers consists ofseven basic sections. A block dia-gram of this receiver appears in Fig.1. Each section may consist of fromone to more than nine stages, de-pending on its function and on thPdesign of the particular receiver. Th.sections can be listed as follows :

1. Front End: antenna plus r -foscillator and mixer stages.

2. Video Strip: video i-f stages,video detector, video amplifiers, d -crestorer, and picture tube.

3. Audio Strip: audio i-f stages,discriminator or ratio detector, audioamplifiers, and loudspeaker.

4. Sync Circuits: sync amplifiersand clippers, horizontal discriminatorand reactance tube.

5. Sweep Circuits: horizontal andvertical oscillators, output tubes, out-

put transformers, and deflectioncoils.

6. High Voltage System.7. Low Voltage System.Knowing the function of each sec-

tion of the TV receiver is essentialfor quick servicing. The first threesections listed above are the signalcircuits. The two signals (video and.audio), coming from the transmitter,enter the front end (Section 1), andbeat with the oscillator frequency.The two i-f frequencies resultingfrom the heterodyning process ap-pear at the plate of the mixer. Oneis the video i.-f., the other the audioi-f.

The video signal then proceedsthrough the video strip (Section 2),,and reaches the picture tube to givethe picture.

The audio signal goes through the

FRONT END

1

FRONTEND

4SYNC CIRCUITS'

1

1

SYNC.AMPS.

VIDEOI F'S

3 AUDIO STRIP

2 VIDEO STRIP

VIDEODET.

HORIZ.OSC.

SWEEP CIRCUITS 5

VERT.OUTPUT

VIDEOAMPS.

HORIZ.OUTPUT

HIVOLTAGE

- -J

Fig. 1 Block diagram of the RCA -630 -TS type receiver. Know-ing the function of each of the sections of this type of receiver

10

is essential for speedy television maintenance. Block diagramsare important in a -m, much more so, however, in television

JANUARY 1950 RADIO AND TELEVISION MAINTENANCE

audio strip;ound.

Part of the video signal is takenJff at the video amplifier and senthrough the sync circuits (Section1). Here the video information is7.emoved and only the sync pulsesIre kept. These are fed to the sweep3scillators to trigger them at theproper time, to prevent the picturefrom being jumbled.

The sweep circuits (Section 5)generate saw -tooth voltages and cur--ents which move the fine stream ofelectrons in the picture tube rapidlyhorizontally and vertically to produce3 raster on the screen. When signalinformation from Section 2 arrivesat the grid of the picture tube (or,in some cases, at the cathode), thebeam becomes lighter and darker,thereby producing the shading of thepicture.

(Section 3) to give the

The high -voltage system (Section6) is of the fly -back type, and mustreceive the horizontal sawtooth inorder to operate. It provides thelarge amount of voltage necessary tobring the beam from the cathode ofthe picture tube to the screen at ahigh enough speed to give the re-quired brightness.

The low voltage system (Section7) is of the standard a -c type. Itprovides the B+ necessary for theoperation of all the other circuits inthe set and the filament voltage foreach tube.

The arrows in the block diagramshow the path of the signal and thesweep voltages, as well as the routeof the d -c voltages.

If a stage in any of these 7 sec-tions becomes inoperative, it has aspecific effect on picture, raster, orsound, or any combination of thethree.

Referring to the block diagram inFig. 1, defects in the various sec-tions will have the following results :Locating Defective Section

If the front end does not operate,two signals are lost : sound andvideo. Result : No sound, no picture..But since the rest of the set is func-tioning, we have a raster. If thevideo strip does not work, there willbe no picture, but there will be soundand a raster. If the audio strip isout, there is a picture, but no sound.With the sync sections not function-ing, sound comes through, but thepicture does not stand still in eitherdirection. If the vertical sweep isout, there is only a horizontal line onthe screen, and sound. If the hori-

zontal sweep is inoperative, there issound and no raster (high voltagedepends on horizontal saw -tooth). Ifhigh voltage does not operate, therealso will be no raster, no picture, butsound. (For that reason, when work-ing back from sound and a blankscreen, both possibilities of trouble-high voltage system and horizontalsawtooth-must be kept in mind.)With the low voltage out, there is nopicture, no raster, no sound.

The troubleshooter just worksbackward. From the effect on pic-ture, raster, and sound he decideswhich section or sections may be atfault, and then makes further checksin that part of the set to get at thefaulty component.

A specific example will demon-strate the application of step one introubleshooting: Isolating the troubleto one of the sections. We assumethe receiver has been functioning andhas developed a fault. The set isturned on and a picture is seen. Butno sound is heard. Off -hand thiswould indicate trouble in the audiostrip (Section 3). However, thisfault might also be caused by mis-tuning of the r -f oscillator, by thevolume control being all the waydown, or by poor orientation of theantenna (the last if the set is on ahigh channel and an adjustable in-door antenna is being used). There-fore, to confirm the diagnosis, thevolume control is turned completelyup. The fine tuning control is ro-tated to see if sound can be broughtin. If it cannot, the channel selectoris switched to all other stations on

-) to page 34

r_

L

FRONT END

VI 6AG5R F AMP

7LO VOLT.

(SEL RECTS.)

V9A V2 7F8CONY.

V9A V2 7F8RE. OSC.

V6-6AU6AUDIO

LIMITER

V2,3,43-6AG5'S

I F. AMPS.

VIOAI/2-12SN7GT

VITA1/2I2SN7GT

SYNCCLIPPERS

SYNC CIRCUITS

3 AUDIO STRIP

V I6-6AL5RATIODET.

IN 34VIDEO

DET.

V7-6507VI2-25L6GTAUDIO AMPS

yIDEO STRIP

V5-6AU6VIDEOAMP

VIIB/2-I2SN7GT

NOR. OSC.

VI4 -I83GTHI VOLT.RECT.

5SWEEP CIRCUITS

VIOB/2-I2SN7GT

0 V8 6SL7GTVERT. OSC.

OUTPUT

6

F- - -

V157JP4 I

Fig. 2 The basic block diagram of the 7 -inch receiver, usingstatic deflection and focusing, inter -carrier sound system, and

an r -f high -voltage power supply. This diagram is essentiallythe same as that shown in Fig. 1, serves the same purpose


New

Development;

For increased gain in fringe area reception

New TWIN DRIVEN YagiAn entirely new antenna which gives out-standing performance in weak signal areas.Matches 300 -ohm line, eliminates ghosts

ACO's new Twin Driven Yagi isJ. a high gain antenna, cut to fre-quency, and designed for fringe areareception on channels 2 to 6. It is anentirely new TV antenna, of fourelements, two of which are drivenand the other two of which are para-sitic. The antenna is equivalent to aYagi system which is energized fromtwo sources. Such an arrangementassures better control of the current -phase relationships of the four ele-ments and, for reasons which we willgo into presently, gives a superiormatch to a 300 -ohm transmissionline. The Yagi antenna, used widelyduring the war, was generally de-signed for a 50 -ohm impedance in-put. The problem which was solvedby Taco engineers was to devise aYagi which would provide a goodmatch to a 300 -ohm transmissionline.

How the match is achieved

This match was obtained by a pe-culiar feeding arrangement developed

for the Taco antenna system. As arule, when a parasitic element isplaced one -tenth wavelength from adriven element, a considerable changeis brought about in the input im-pedance of the driven element. Thereason for this change is the factthat a transformer action takes placebetween the driven and the parasiticelement. It is this reaction which re-duces the operating impedance of aconventional Yagi system to an ex-tremely low value.

The Twin Driven Yagi is not af-fected by this loading condition be-cause the director system, which ismade up of one parasitic element andone driver, is fed by an impedancematching network from the maindriven element. Through this ratheringenious system, Taco has developeda four -element array which is wellmatched for a 300 -ohm system. Forlow signal areas, a single bay isusually sufficient.

For increased gain in sub -fringeareas, two single units can be stacked

CHANNEL10

W..Jo 9a.a

8

z 7wixW u- 6

K0 51-

c3 4.ce4a. 3z0U, 20z I

z40 50

-1 2 J 3 1 4 I I 5 I 6 I

TWO BAY SINGLE BAY

55 60 65 70 75 80 85 90

efficiently by using a Taco -developedtransmission line. Use of this lineassures a 300 -ohm impedance matchat the center terminals. This is animportant factor, since there will beno loss in input impedance whenstacking two single units, and nomismatch will result.

The curve in Fig. 1 shows themeasured voltage gain (in db) of thenew antenna as compared to a refer-ence dipole, for both the single andthe two -bay system.

Fig. 2 shows the horizontal radia-tion pattern for the Twin DrivenYagi. As can be seen, the beamwidth of the antenna array is verynarrow. This means that extremecare must be taken in orienting theantenna and that it can be used to,good advantage with a antenna ro-tating device. It is also apparentfrom a study of Fig. 2 that the an-tenna has a high front -to -back ratio;and it is therefore especially recom-mended for areas with co -channelinterference. "

NO°

210°

180°

150°

120°

270° 300* 330'69 MEGACYCLES ..wq,-..-,SINGLE 80101

/ \ --- ,-TWO BAY dia.

1111/111/,-,

gj-,sistrairs&--,.=1 . ram=

- ---

.'- RELATIVE POWER

N-''--INPUT TO RECEIVER II/4

iioreelealparial

,,-.-t Milltitc.M__ 111, c.qW490* 60 30°

345

0

15°

Fig. 1 Measured gain of new antenna in db, compared to stand-ard dipole. Curves are for both signal and two -bay arrays

12

Fig. 2 Horizontal radiation pattern of Twin Driven Yagi, forboth single and two -bay arrays, measured at 69 megacycles

JANUARY 1950 RADIO AND TELEVISION MAINTENANCE.

"Like having someone to run interference for me on everysale!" Radio -TV servicemen feel that way about the GeneralElectric trademark because experience has shown how highlytheir customers respect the symbol "G -E".

This is only the start of the G -E dealer -profit story. ForGeneral Electric helps you with an unexcelled group of tubepromotion aids-income-builders every one! G.E.'s completeline of tubes includes newest types made possible only bysuperior resources in research, development, and manufacture... meaning that you can go after all the tube business, all the time!

Unwrap this G -E dealer success -package! Give your skill andefforts as serviceman a rich reward! Your G -E tube distributorgladly will cooperate in every way. Phone or write him oday!Electronics Department, General Electric Co., Schenectady 5, N. Y.

eoee mil/bleb/pea cw/eance

GENERALS ELECTRic,

ONE SOURCE FOR

ALL YOUR TUBE

REQUIREMENTS!

-also GERMANIUMDIODES and SELENIUMRECTIFIERS. Stock G -E100 -percent, t, save timeand routine in ordering-to have the benefit of bulkdeliveries from your dis-tributor-to orofit fromGeneral Electric 'ube qual ity and produc- popularity,


How to

CONSTRUCT

the 1950

MODERN

SERVICE

BENCH

By The Staff of

Radio & Television Maintenance

IN designing a new service benchto cover all the essential needs of

servicing and laboratory work inradio, television, and electronics, agreat number of problems are en-countered. Some of these have beensolved and developed in the designand models of the bench describedin this article. Others have beencompromised because of limitationsof space and position, as opposed tooperating needs, size, and optimumlocation of various equipments, andseveral other factors.

The former radio service benchdesign described in the February '46issue of RADIO MAINTENANCE MAG-AZINE, was far simpler in designthan the present model. The reasonfor this is that the requirements atthat time were considerably less com-plex than they are today.

Preliminary analysis showed aneed in a radio service bench for thefollowing: Space for service man-uals, test equipment, power and con-trol facilities, tools, most used, re-placement parts, and a receiver.

complete plans, parts list, and instructions forbuilding this custom designed service bench

There are, in addition, some otherincidental requirements (props, testspeaker, panel details, etc.).

Teleset problems

In earlier designs of a servicebench, TV was a minor factor. Al-though it was taken into account,95% of all the telesets were of thesmall -tube variety, and hardly affect-ed bench design. The situation isdifferent today. For the bench de-signer, the greatest single problem istelevision maintenance - includingservice, repair, and alignment. Toservice a TV receiver of the 16" -tubevariety properly, the width and depthof the bench top required is far inexcess of the ordinary bench in usetoday. True, you can service a tele-set on the old size bench-usuallykitchen - cabinet - size - designed inheight and depth, and about six feetin width-but you cannot do so effi-ciently. The old size and location re-quirements led to the design of abench with all meters, tools and otherneeded equipment within easy reach.

But new space requirements of thelarger television sets themselves makeit necessary that the meters and otherfacilities be set further back on thebench (by as much as a foot and ahalf) and that they be raised (by sixinches), in order to accommodate theset and still leave ample workingspace for efficient service.

In designing the new bench, ourpurpose was two -fold : Improvingthe design of the former bench to ful-fill present day service requirements,and reducing the cost for parts to..below $100.

Design details

To begin, in laying out the design,standard kitchen cabinet top heightwas chosen, so that advantage couldbe taken of the price of mass pro-`duction units, thereby lowering thecost. For the cabinets, Sears, Roe-buck & Co. model 1K0601 (Fall -Win-ter Catalog) was selected. Modelswere built using this cabinet (topdrawer, two shelves, and doors), anda model having four drawers. After


FIG.1

2'

SECTION A -A

0

RADIO & TELEVISION MAINTENANCE

MODERN BENCH DESIGN FOR 1950

3 ANGLE IRON BRACES

0ACROSS TOP

I=1

Ii

8'

1

o 14

L

r--------

II

1_1

II3-1-8 OVAL HEAD WOODSCREWS,NICKEL PLATED WITH

- COUNTERSUNK NICKEL PLATEDWASHERS.

8 FLAT HEAD SCREWS

8-2"-t0 FLAT HEADWOOD SCREWS INWORKING SURFACE

5 ANGLE IRON BRACESUNDER WORKING SURFACE

2Scale0 Feet


'.4iiiriftthw~49.4,C.voomomb.K

I

TABLE I

PARTS LIST

DetailNo.

Name Material Quantity

1. Top 1/2" Plywood 1

2. Bookshelf 1/2" Plywood 1

3. Working Surface 1/2" Plywood 1

4. Side 1/2" Plywood 25. Upper Back Panel 1/2" Plywood 1

6. Lower Back Panel 1/4" Plywood 1

7. Left Instrument Panel 1/8" Tempered Masonite 1

8.. Right Instrument Panel 1/8" Tempered Masonite 1

9. Front Brace 1/2" Plywood 1

10. Top and Shelf Brace 3/4" White Pine 1

11. Drawer Front 3/4" White Pine 212. Door 3/4" White Pine 41.3. Cabinet Side 1/2" Plywood 41.4. Foot Board 1/2" Plywood 215. Horizontal Door Frame 1 1/4"x3/4"x2'White Pine 416. Horizontal Drawer Frame 2"x3/4"x2' White Pine 217. Vertical Door Frame 1 1/4"x3/4x2' 7 1/2"White Pine 418. Cabinet Shelf 1/2" Plywood 419. Drawer Bottom 1/2" Plywood 220. Drawer Side 1/2" White Pine 421 Drawer Back 1/2" White Pine 222. Brace 3/4"x3/4"x3'-11" White Pine 223. Brace 3/4"x3/4"x3' White Pine 224. Brace 3/4"x3/4"xl'-2"White Pine 225. Brace 3/4x3/4"x2'-4" White Pine 226. Brace 3/4"x3/4"xl'-6"White Pine 227. Brace Panel 3/4"x3/4"x3' White Pine 228. Brace 3/4"x3/4"x11" White Pine 229. Brace, Surface 3/4"x3 3/4"x2' 11 1/2"Wh.Pine 230. Drawer Slide 1"x3"x2' White Pine 431. Shelf Support 3/4"x3/4"x2' White Pine 832. Brace 3/4"x3/4"x1'4"White Pine 233. Shelf Bracket 6"x8" Steel 1

TABLE II

LIST OF MATERIALS TO BE PURCHASED

Quantity Material Use (Detail numbers)

51 sheets 8' x4' x1/2" Plywood (1-2-3-9-14-4-13-18-19-5)1 sheet 8'x4'xl/4" Plywood (6)'1 sheet 4'x3'xl/8" tempered masonite (7-8)1 sheet 16"x15"x3/4" White Pine (10)91 ft. l'x3/4" White Pine (12-11)181 ft. 1 1/4"x3/4" White Pine (15-17)4 ft. 2"x3/4" White Pine (16)12 ft. 3"x1/2" White Pine (20-21)43 ft. 3/4"x3/4" White Pine (22-23-24-25-26-28-31-32)12 ft. 3-3/4"x3/4" White Pine (27-29)8 ft.68832

18

3

8

12418012421618

1"x3" White PineDoor PullsKitchen Cabinet Hinges3/4"x3"x3/16" Angle Iron Braces1" - No. 8 Flathead angle IronBrace Screws3/4" -No. 8 Oval Head Screws,Nickel Plated1" -No. 12-24 Flathead MachineScrews, Nuts, and Washers1 -3/4" -No. 1-20 Flathead MachineScrews, Nuts and Washers3/4" - No. 8 Flathead ScrewsFriction Catches1" - No. 8 Flathead Screws3/4" - 8 Flathead Screws2" - No. 10 Flathead Screws11" - No. 8 Flathead ScrewsCountersunk Washers, NickelPlated

(30)

1 Stanley 796-1 (6"x8") Bracket (33)

extensive testing it was concluded'that shelf space with doors was moreconvenient for radio parts storagethan drawer space, with the top'drawer being used in both cases forthe storage of tools.

In the preliminary design of thebench, the test equipment panels wentstraight across the bench, at a 30°angle with respect to the vertical, be-ginning at a normal distance of twofeet from the front.

When a 16" teleset is placed diag-onally on such a bench, however, itssides would protrude considerablyover the edges of the bench. Thisliquidated that type of panel design.The next design was a tapering panel.with a table top one foot deeper.After many sizes and shapes of setshad been placed on the bench andanalyzed, the one shown was chosenfor a test equipment panel with spacefor at least four instruments, and acenter panel space for a large multi-'meter.

VisibilityThe instruments on the two diag-

onally placed panels are within easysight reach for the size meter ( four-.inch scales) ; and the back panelmeter, placed three feet from thefront of the bench, has a large enoughscale (7 x 8") to be highly visible.An outlet plate was also placed atthe back of the bench for 110 voltsa.c. and 6 volts d:c., as shown. Theswitch on the right was intended forthe control of a fluorescent fixture tobe located over the lid of the bench,and the left hand switch to turn on a6 -volt auto power supply, intendedto be located at the rear of the bench,and wired to the outlet adjacent to,the switch.

After the bench was designed andmodels built, it was found by experi-ence that the power outlets were toofar in the rear; and it is thereforesuggested that a plug-in strip bemounted instead on detail #9, thefront brace underneath the bench top.

ModificationsProvision for manuals was made

in the remaining spare section.Please note that the height called for tthis is 16", to provide for the newRider TV Manual. The cover hasbeen put on top to serve as dustcatcher. It has been suggested how-ever that the dust cover is not neces-sary, that lumber can be saved andthe appearance of the bench im-


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proved, and its height reduced, byfashioning the top in book case style,with detail #4 cut down six inches,and its front upper corner roundedwith a radius of approximately threeinches; as well as detail #5 cut to3' 6" from its height of four feet.

If the overall height of the benchneed be reduced because of the heightof the ceiling, it is recommended thatthe space between the work benchand detail #7 and #8 be reduced to14", that details #7 and #8 be re-duced to 12" in height, and that theopen book case style, discussed above,be used.

Construction

The large sections of the benchare cut from plywood sheets, 5Y2 ofwhich are required. This type ofconstruction simplifies the problemsof bracing and assembly and givesgreat strength. Many supply houseshave the necessary equipment andwill cut the plywood pieces to size fora small charge. It is suggested thatthe reader take advantage of such aservice if it is available. Since thelarge sections of plywood are diffi-cult to handle and transport, the pricepaid will be well worth while.

If you have the sheets cut by alumber supply house, have themmake the long straight cuts, and dothe smaller cuts by hand later. Forexample, have the piece from whichthe two sides are made (detail #4)cut across its short dimension, as in-dicated in Fig. 4, and then cut in halflengthwise, leaving the small cuts(where the top of the superstructureis cut back) to be made by hand.

While complete information hasbeen given in the drawings for theconstruction of the two storage cab-inets, the reader who is short ontime and long on cash can substitutecommercial units for them. TheSears, Roebuck & Co. unpaintedknockdown cabinets (see above) willfit exactly. These units are avail-able with a single drawer and doors,or with several drawers. If com-mercial units are substituted, theirtops should be discarded, as they areunnecessary.

After the large plywood sectionshave been cut to size, the smallerparts should be made up. The readerwill note that several of the partsare marked "cut to fit" on the detaildrawings. These parts should not bemade up until they can be fitted intoplace, at which time they can be cut

and planed to an exact fit.The Masonite test equipment pan-

els may be cut to size, with the ex-ception of the small notches whichshould be made when the panels arebeing fitted into place.

Assembly

After all of the parts have beenmade up, the job of assembly begins.The cabinets should be assembledfirst. The following is a step-by-stepprocedure for assembling them:

1. Fasten the drawer and shelfsupports ( #30, 31) to the sides.Each drawer support is held in placeby three 2" #10 flathead woodscrews, inserted from the outside.Clearance holes for the screwsthrough the plywood sides should bemade with a 1/16" drill. Counter-sinking is unnecessary since thescrews will countersink themselvesif they are turned in very tight. Theshelf supports (31) are fastened witha 1" #8 flathead woodscrews, insert-ed from the inside.

2. Fasten the shelves (#18) inplace. Fasten the lower shelf andthen the upper, using six 1" #8 flat-head wood screws for each.

3. Fasten all the front cross pieces(#14, 15, 16, 17) in place, usingPA" #8 flathead screws.

4. Assemble the drawers, using theparts indicated on the detail drawing(#11, 19, 20, 21), using 1" #8 flat-head wood screws.

5. Mount the doors, using kitchencabinet door hinges and 72" #8 flat-head screws, or those supplied withthe hinges.

6. Mount the working surface sup-ports (#29), using 1" #8 flatheadwood screws.

7. Place the cabinets in the relativepositions they will have in the benchand fasten the back piece (#6) tothem, using twelve g" #8 flatheadwood screws. These screws shouldbe fastened into the back end of thedrawer and shelf supports (#30,31).

8. Fasten the front working sur-face brace (#9) in place, using four2" #10 flathead wood screws. Thescrews go through the front braceinto the front ends of the left andright hand working surface braces(#29).

9. Mount the superstructure sides(#4). The sides should be mountedin the following manner: take oneside panel and, holding it in place,drill four holes through both the

side panel and the cabinet to clewthe 14"-#4-20 flathead machinscrews which are used to fasten thsides to the cabinets. The positiolof these holes is indicated on Fig. 2

10. Mount the working surfacsupports (#28), using 1" #8 flathead wood screws.

11. Place the working surface iiposition, and fasten it with eigh2" #10 flathead screws and six 1'#8 flathead screws. Four of thi2" screws fasten to the f ront-to-baclsupports (#29). The others anfastened to the fronts of the cabinet(#16). The 1" screws are fastenecto the corner supports (#28).

12. Mount the two back corne.braces (#23) using PA" #8 flathead screws, placed from the insideout.

13. Mount the top supports (#26;using 1" #8 screws, placed from theinside out.

14. Mount the upper back sectios(#5), using 1" #8 flathead screwsfastened into the back corner braces(#23) from the outside.

15. Mount the back shelf supports(#22), using eight 1" #8 flatheadscrews, fastened from the inside out.

16. Mount the side shelf supportg(#32), using 1" #8 flatheadscrews, fastened from the inside out.

17. Mount the book shelf (#2)susing 1" #8 flathead screws fastenedfrom the top down.

18. Mount the top (#1), using1" #8 flathead screws, from topdown.

19. Mount the eight small anglebraces, three to back top, three toback bottom, and two to front brace(#9), using W' #8 screws.

20. Mount the top and shelf braces(#10, 33). Use nine 2" #10 flat-head screws, three on top, three inthe back, and three on the bottomof the top brace (#10). Use 1"#12-24 machine screws for the backof the shelf brace (#33).

21. Mount the lower test equip-ment panel brace (#27), using 2"#10 flathead screws, two in back,and two in side end. These brace;are cut to fit at the time of mounting.The front edge must be beveled tofit the slanting test equipment panelsHowever, they should be mounted inplace temporarily, and the planingleft until the panels are being fitted,into place.

22. The side panel and top panelbraces (#24, 25) should be mounted,

- to page 38


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late receiver model introduces new

FLYWHEEL

SYNC CIRCUITSby Morton G. Scheraga

Allen B. DuMont Labs.Co-author Video Handbook

A review of flywheel sync circuits found in earlier telesets and a dis-cussion of the improvements which have been made in G -E's TV model 820

THE advantages of flywheel synccircuits in TV horizontal sweep

systems have been amply demon-strated. They give the receiver agreat immunity to noise signals; andmake possible good pictures in weaksignal areas with low signal-to-noiseratio, or in strong signal areas wherenoise signals may be great.

In the triggered -sync system whichwas used in all receivers severalyears ago, the frequency of thesweep oscillator was controlled byeach successive sync pulse. If noisecame through with the sync signal,the sweep oscillator would momen-tarily lose synchronization and causeseveral lines of the picture to tear.This effect was more troublesome inthe horizontal than in the verticalsweep system. For this reason, themore expensive flywheel sync circuitswhich were developed were used onlyto control the horizontal sweep oscil-lator.

With a flywheel sync system, thefrequency of the horizontal sweeposcillator is controlled by a d -c volt-age on its grid. This voltage resultsfrom the phase difference betweenthe incoming sync signal and a volt-age wave obtained from the outputof the sweep generator. The d -c volt-age thus produced is called an auto-matic frequency control (a -f -c) volt-age. It takes many successive cyclesof the incoming sync signal and thesignal from the sweep generator toestablish the level of the d -c voltage.If a sudden noise burst over -ridesthe sync signal, it has little effect onthe a -f -c voltage, and the oscillatordoes not lose synchronization. In ef-fect, like a flywheel, the circuit isimmune to sudden changes ; hence itsname.

Until recently, two types of a -f -c

sync systems were used in televisionreceivers. These have been in ex-istence for several years and mosttechnicians are familiar with them.It is, however, well to review theiroperation briefly before discussingthe latest circuits.

Early flywheel sync

The first a -f -c sync system tomake its appearance is shown in Fig.1. The horizontal sync pulses andthe sawtooth voltage generated in thehorizontal discharge -tube circuit arefed to a phase detector. If the twovoltages are out of phase, a d -c volt-age is produced in the detector. Thisvoltage is proportional to the amountby which the sawtooth generator isoff frequency from the sync pulses.The filter network removes noise sig-nals from the d -c voltage, which isthen amplified and fed to the grid ofthe sweep oscillator. The d -c bias onthe grid changes the frequency of theoscillator, so that it falls into syn-chronization with the incoming syncpulses.

A later variation of this circuit isshown in I. ig. 2. Again the horizon-tal sync pulses are fed to a phase de-tector, but this time the phase -com-parison voltage is a sine -wave whichis generated by a stable Hartley os-cillator. The free running speed ofthe oscillator is 15,750 cps.

If this sine wave signal and thesync pulses are not exactly of thesame frequency and phase, a d -cvoltage is produced by the detector.The d -c signal is filtered by a filternetwork to remove disturbing, high -frequency noise, and is then fed toa reactance tube. The reactance tubeis connected in parallel with the tankcircuit of the Hartley oscillator. Areactance tube circuit acts like a vari-

able inductance or capacitance, de-.pending upon the amount of signalon its grid. This inductance or capac-itance in parallel with the tank cir-cuit of the oscillator affects the oscil-lator frequency. The d -c signal fromthe phase detector causes the re-,

actance tube to change the effectivecapacitance or inductance across thetank circuit by an amount whichmakes the osillator frequency thesame as that of the incoming syncpulses.

In the plate circuit of the oscilla-.tor, a differentiating circuit is em-ployed to derive triggering pulseswhich are used to synchronize thesawtooth generator.

Latest flywheel sync circuit

Both of these a -f -c circuits work -well and are employed in many ofthe latest receiver models. More re-cently, another flywheel sync circuit,has been introduced which performsequally well, but has the advantageof being lower in cost. It requiresfewer tubes and components. A'schematic diagram of this circuit, asit appears in the G -E model 820, isshown in Fig. 3.

The horizontal sawtooth generatoruses one section of a 12SN7(V12B), connected in a blocking os-cillator circuit. Instead of its fre-quency being directly controlled bythe horizontal sync pulses, it is con-trolled by the adjustment of the oper-ating bias on the grid of the tube.A control tube, consisting of theother triode section (V12A), com-t-pares 'the phase between the incom-ing horizontal sync pulses and theblocking oscillator frequencies, andproduces a voltage proportional tothe phase displacement. This voltageis applied as bias to the grid of the _


blocking oscillator tube, V12B, andresults in the oscillator frequency be-ing maintained at the proper phaserelation with the incoming sync sig-nal. Thus far, the circuit is the samein principle as those previously de-scribed. The important differencearises from the method by which thecontrol tube generates the d -c a -f -cvoltage.

Several signals are fed simultan-eously to the control tube V12A. Theincoming sync pulses (waveform Ain Fig. 3) are fed to the grid. Thesawtooth voltage (B), generated inthe plate circuit of V12B, is mixedwith the integrated output (wave-form C) of the horizontal sweep am-plifier tube and produces waveformD, which is also fed to the grid ofV12A.

V12A obtains its operating bias bybeing connected to the grid circuitof blocking oscillator V12B throughresistor R51. The blocking oscilla-tor produces a large negative bias inits grid circuit during its normaloperating cycle. When the horizontalsync pulses (waveform A), or thecombined output voltage (D) areimpressed separately on the grid ofV12A, they do not have sufficientpositive amplitude to cause appre-ciable plate current flow in tubeV12A. However, when they are fedsimultaneously to the grid of V12A,they rise above cut-off bias and causethe tube to conduct. The amplitude

'of the signal which rises above thecut-off bias, and hence the conduc-tion time of the tube, depends uponthe phase relationship of waveformsA and D. Three different phase con-ditions are shown in Fig. 4.How if operates

During conduction, capacitors C86and C78 become positive with re-spect to ground. Since resistor R50is in the bleeder circuit across thefilter and also forms a part of thegrid return circuit for the sweep

to page 34

Fig. 1 Block diagram of the first a -f -c syncsystem.

Fig. 2 Block diagram of a later version of:lywheel sync circuits. Phase comparisonvoltage is sine wave, generated by Hartleyoscillator.

Fig. 3 Schematic diagram of latest synccircuit, as it appears in G -E's Model 820.

Fig. 4 Three different phase conditions ofsignals in a -f -c circuit. Each condition isindicated in diagram.

PHASE FILTER D -C SWEEP SAWTOOTH 11'INCOMING DETECTOR NETWORK AMP. OSC. GENERATOR

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FIG.4


Latest

More compacttelesets coming with new

RECTANGULAR

Picture Tubepicture tube design developments

promise improved receivers in near future

As is well known, the aspect ratio(the ratio of length to height)

of the transmitted television pictureis four by three. Until now, no re-ceiver on the market has been ableto utilize this transmitted picture, orthe tube face, fully because the pic-ture tube in the receiver was round.

Three methods have been em-ployed to show the rectangular pic-ture on a circular screen :

1) Showing the entire picture be-ing transmitted on the tube face.Doing this leaves approximately 25%of the tube face unused (and gen-erally masked). This condition isillustrated in Fig. 1A.

2) Enlarging the 4 x 3 trans-mitted picture so that its verticaledges were tangential to the roundsides of the tube, losing the cornersof the transmitted picture (Fig. 1B).

3) Expanding the picture until thetop and bottom of the transmittedimage were tangential to the upperand lower part of the tube. This

filled the whole round tube face withthe image, but over 38% of the tele-vised image was lost (Fig. 1C).

A tube is now available whose faceis rectangular with an aspect ratioof four by three. With a tube ofsuch construction, no part of the pic-ture is cut off, and no part of thescreen remains unused, as illustratedin Fig. 1D.

The 16 -inch rectangular tube an-nounced by Hytron provides a pic-ture of 10%" x 12y2", or a viewingarea of approximately 140 squareinches. Conventional tube screensshowing a picture of the same pro-portion, take up appreciably morespace.

Production difficulties

The new tube will play an im-portant role in the design of futuretelesets. Hytron has already suppliedsamples of the new 16RP4 to a largenumber of manufacturers, and hasdefinite production orders from manyof them. Since the new tube, though

of the 16 -inch type, takes up onlythe space of a conventional 12" tube,we can expect more compact re-ceivers in the near future.

One might wonder why the rect-angular tube was not produced in thefirst place. The reason for this liesin the manufacturing process of tubeenvelopes. When the tube face issealed to the tube funnel, the twoare fused together under intenseheat. In order to assure a satisfac-tory fusion, the heat which is appliedto the various areas must be of uni-form temperature. With circulartubes, this problem was easily solved.While the face and the funnel wererotated on the tube axis, a stationaryflame was applied to the surfaces tobe fused. Because the face and fun-nel were round, the distance be-tween the rotating tube and the flamewas constant, and the heat thereforeuniform. It was, however, a differentstory with rectangular tubes. Whena rectangular tube is rotated, the dis-tance between any point on the, tubeand any other stationary object doesnot remain constant, and the heatwhich would be applied to such atube would not be uniform on thevarious surfaces, making the seal im-perfect. This problem has only nowbeen solved.

There are some other features ofthe Hytron tube which are worthmentioning: the use of lightweightglass plus the rectangular shape makeits weight only about 70% of con-vention 16" glass tubes ; there is nohigh -voltage isolation problem of thetube itself ; a relatively flat face in-corporates a neutral gray density fil-ter to increase contrast; and an ex-ternal conductive coating, which actsas filter capacitor when grounded,provides shielding action against ex-ternal electrostatic fields. '

Fig. 1 Reproducing rectangular transmission on circular corners of picture lost. C) Tube face area completely utilized.screen. A) 25% of tube face area lost. B) 14°0 of face area. 38% of picture lost. D) No loss of tube face or picture area


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essential knowledge of television! Inside thecovers of the VIDEO HANDBOOK is presentedcomplete up-to-the-minute information on tele-vision arranged for quick reference-in easy toread, non -mathematical style.

The VIDEO HANDBOOK is designed to giveyou the practical . . . answers to all )our ques-tions on television-the complete, detailed pro.cedurea on all phases of television work-stepby -step explanations for everyday problems. Thisbook provides the ready information to makeyour television education complete.

The VIDEO HANDBOOK will save you time-improve your efficiency and make your workeasier. It provides the knowledge that meansmore profit for you. Every page adds to yourbackground for greater prestige and income.Here is the means for everyone in television-employed and xecutive-to increase his valueto his firm.

This book is more than a source of informa-tion and interesting reading-it is an investmentin your future in television.

THE RADIO DATA BOOKthe only radio handbook of Its kind . .

over 900 pages ... 12 sections, each cov-ering a radio subject more completelythan any other book!

Used by Engineers, Servicemen, Designers.Laboratory Technicians. Draftsmen, Operators.Inspectors, Amateurs, Experimenters. ResearchDevelopment, Consultants. Broadcast Technicians.Planners, Installation Men, Military, Marine.Police, Fire, Forestry and Railroad Communica-tions.

ANYONE and everyone in radio and elecironies ran use this book!

Plan every operation in radio and electronicswith the Radio Data Book. This new radiobible will be your lifelong tool . . . you willuse it every day, on the board, at the bench, inthe field! Uwe it for engineering, constructiontroubleshooting and testing. The RADIO DATABOOK will be your invaluable aid in design, ex-periment and In layout. It will help make yourproduction better, faster and easier. In any andevery operation in radio and electronics, youwill use the RADIO DATA BOOK!

CONTENTS:

Section I. THE 150 BASIC CIRCUITS IN RADIOSection 2. COMPLETE TEST EQUIPMENT DATA

Section 3. TESTING, MEASURING AND ALIGNMENTSection 4. ALL ABOUT ANTENNASSection 5. SOUND SYSTEMS

Section 6. RECORDING

Section 7. COMPLETE TUBE MANUALSection 8. CHARTS, GRAPHS AND CURVES

Section 9. CODES, SYMBOLS AND STANDARDSSection W. 50 TESTED CIRCUITS DESIGNED FOR OPTIMUM

PERFORMANCESection 1 I. DICTIONARY OF RADIO AND ELECTRONIC

TERMS

THE RADIO & TELEVISION LIBRARY IN ATTRACTIVE

Section I.Section 2.Section 3.Section 4.Section 5.Section 6.Section 7.Section 8.Section 9.Section 10.Section II.Section 12.Section 13.Section 14.

THE VIDEO HANDBOOK

CONTENTS:Television: Past, Present & FutureFundamentals of electronic TelevisionThe Television StationThe Television ReceiverTelevision Antenna SystemsCreating a Television ShowDescriptions of Modern Television ReceiversInstalling Television ReceiversServicing Television ReceiversTelevision Test EquipmentBuilding a Television ReceiverData SectionTelevision TermsBibliography

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(BusinessManagement How to set up a

PERPETUAL INVENTORY SYSTEMby Betty Lee Gough

How can you determine whatmerchandise is wanted by

enough customers to make selling ita profitable operation? How can youdetermine the quantities to carry instock ? How can you be sure whento re -order ? Or in what quantities ?When prices change, how can youinsure the right markup, so that allof your stock-the old and the new- will carry a satisfactory profit?The answer to all these questions issimple : a perpetual inventory system.

The old fashioned method of "tak-ing inventory" at periodic intervalshas been replaced today with the per-petual inventory. Instead of prac-tically stopping work every three orsix months and tying up the businessin a tedious counting job, good busi-nessmen today keep their inventoryrecords in a card file, taking physicalinventory (counting all items instock) not more than once a year.

The perpetual inventory offersmany advantages besides the savingin overhead. It is easy to keep. Afew quick notations give a completepicture of your reserve stock situa-tion at all times; and it can be usedas a efficient pricing tool. An inven-tory which does all these things

Accurate records make for good management. Here'san efficient system to make you a better businessman

should be pretty complicated. Butin practice is it not. All you need issome file cards (8 x 5's do the jobwell) and a place to keep them (forinstance, a visible reference file ofthe Kardex type, a card cabinet, oreven a shoebox).

Each card has space at the top forthe name of the product, its manu-facturer, your distributor's name,and your stock number. There is alsospace at the top to show maximumand minimum stock you should keepon hand, as well as the markup theitem should carry.

The maximum can be determinedby good horse sense. It is the num-ber which you can expect to sell inany given period, 2 months, 3months, a year, etc. The minimumstock is the smallest number of itemswhich will carry you over-should asudden heavy demand arise-untilyou can replace stock in a normalway.

Here is an illustration of how thisworks : You sell Blank Batteries. Ifyou order new stock, it would takethe wholesalers six days to deliver itto you. During these six days, youwould ordinarily sell four Blank Bat-teries. Sometimes during peak sea -

ITEM Crr)70-4-Pt go-Mitx,4-

Sold by

Stock no. 8"2-8

Maximum loMinimum 10

Mark-up 309

No.8 Dote Purchased (I) No 8 Dot. Drown out (2) Totol on Hand(3) COO (4) Unit Cost(5) ExteoSt (6) Selling Price (71

2o 5/11/19 20 2 fo J.?. oo /Zoo /67" 6 o

2 5/29/19 /1If (///49 7

/3 6/2/49 2o /0.6o 12.50 r?: 3o IS: 99

Fig. 1 Here's how perpetual inventory card looks when in actual use. At one glanceyou obtain all information necessary to keep your supply problems well managed

sons, however, you sell as many atforty in six days. So to be safe, youwould need forty batteries to tideyou over till new stock arrives. Fortythen is the minimum stock youshould keep in reserve. Mark thisnumber on the card and, when sale:reduce your stock to forty, you canreorder.

Reordering is easy

The beauty of the perpetual inven-tory system is that it not only tellsyou what is on hand every day, b. 'also tells you when to reorder.

Below the information on top ofthe card, the cards should be ruledas shown in the illustration. Thevertical columns should be headed :Quantity Purchased, Quantity DrawnOut, Total on Hand Unit Cost, Ex-tended Unit Cost, Selling Price.

As you buy stock, enter the quan-tity and date in the first column, andthe total number this puts in yourstock in column three. Enter cost ofthis order in column four. The unitcost (total cost divided by numberof pieces) goes in column five. Toget the figure for column six, takethe cost of all items of this merchan-dise in stock and divide by the num-ber of items (including those youjust purchased). This gives you theextended unit cost, which is an aver-age cost for everything in your stock,taking care of price rises and reduc.tions. Selling price is entered in thelast column. You obtain it by addingyour markup to the extended unitprice.

On the horizontal columns, markthe dates on which you draw outmerchandise from reserve, and thedates on which you add to it.

How it works

To illustrate how effectively thisperpetual inventory system workswe'll consider the case of Joe Brown,


vho operates a service organizationn Main Street.

Joe's present volume of sales runslose to six figures yearly. He keeps. sizeable stock on hand, and special-zes in low -profit, high volume sales.iince he has changed to the per-tetual inventory system, he finds thatLe does not "run out" of his fastnoving items as he formerly didwhen he looked around the store tolecide when orders should be sent tohe jobber.

Portable radios are his fastest sell-ng line. They move so fast that hetas to keep at least 10 on hand at allimes. His normal inventory is about!0. So on the perpetual inventory:ard 20 was marked in the "maxi-num" box and 10 in the "minimum."['he portables cost him $12.00 andie expects to get a markup of 30%na them. So 30% goes into thenarkup indicator. The selling price,vith 30% markup added, is $15.60.

On June 1 the records indicatedhat 18 portables were in stock. On

A date Mr. Brown took out 11 to-eplenish his low floor stock. The-ecord now showed 7 left in reserve,ess than the minimum he wanted onland. So an order for 13 was tele-Atoned to the wholesaler, bringing:he reserve back to 20.

When the sets arrived, he discov-ered that the price had gone up toF12.50 a piece.

Extending his unit cost by aver-aging the costs of the 7 sets he hadNI hand, and the 13 he had just or-lered, he found that the average (orextended) unit cost of his total stockNas $12.30. So $12.30 was enteredn column six. Marking up this fig -ire by 30% gave Mr. Brown $15.99For his new selling price. The $15.99illowed a fair markup on the newstock, and increased the markup onhe old only enough to give him afair selling price for the total stock.!n this way he made sure that hisarice would be competitive, yet stillallow him a reasonable profit.

Of course, the perpetual inventoryan never completely replace thecount 'em" method of keeping in-

ventory. But it can make the count -hg less of a chore, and one that canaafely be done not more than onceL year. The physical inventory servesus a check on the perpetual inven-tory setup. It is vitally necessary tonake this physical check once every:ear, because doing so is the only

to page 29

RADIO AND TELEVISION MAINTENANCE

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3.

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QUESTION-Who has built 95% of all conical antennasinstalled toc.ay?ANSWER-Telrex! Leadership in engineering and qualitykeeps Telrex out in front. The Telrex staff is ever seekingbetter methods, improved materials and design advance-ments. Supply a Telrex antenna on your next TV installa-tion-you'll see the difference!

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HIGH VOLTAGE COUPLERCONTROL

To provide safe insulation for con-trols used in high -voltage circuits,Clarostat has now available a high -voltage coupler feature which theywill incorporate on request in most oftheir controls when ordered. Knownas the type 56-125 high -voltagecoupler, this feature makes use of aplastic straight -through shaft, insteadof the previous insulating strip joiningseparate sections of the metal shaft.This eliminates backlash and providesmore critical settings. An insulatingtube isolates the control proper fromits mounting bushing. The control -to -ground breakdown rating is betterthan 10,000 volts. For full details, getin touch with Clarostat Mfg. Co., Inc.,Dover, N. H.

3"-OSCI LLOGRAPHA successor to the I64 -E has just

been announced by DuMont: the 3 -

inch type 292. Very portable instru-ment, incorporates features found pre-viously only in 5" models. Weight is

2; lbs, dimensions I07/8" x 81/8" x I I".Deflection sensitivity 0.4 rms volt/inch(vertical) and 0.56 rms volt/inch (hori-zontal). Flat tube face minimizes opti-cal distortion. Recurrent sweeps from 8tc 30,000 cps are supplied, and bal-anced deflection is used. Full info ob-tainable from DuMont Labs, 1000Main Ave., Clifton, N. J.

NEW ANTENNA LINECornell-Dubilier has just introduced

the first model of its Skyhawk antennaline. It's called the Skyhawk Strafe -Line, comes in 5 models, all with hi -locoverage. Model 85X has 8 -foot mast,phase line, 6 standoffs & base mount-ing bracket, T85X is similar but comeswith 60 -inch transmission line. Model85XAX is double stacked 85X withfeeder bars, 6 standoffs, 8 ft -mast,phase lines & base mounting bracket.T85XAX is same model with 60 -inchtransmission line. Model K85X is single85X bay, feeder bars, 1.1' bolt mastbracket for converting single todouble stack. For details, write Cor-nell-Dubilier Electric Corp., SouthPlainfield, N. J.

MINIATURE RESISTORSTwo new miniature resist6rs have

been announced by IRC, completingits line of IRC BT Insulated ResistorsThey are 1/3 watt and 2 -watt units.Type BTR at 1/3 watt meets JAN -RC 10 specifications, and type BTB at2 watts is equivalent to JAN typeRC40. They have filament type re-sistance elements, making for low op-erating temperature and good powerdissipation. Phenolic resin providesmoisture protection. Both are charac-terized by their small size. Interna-tional Resistance Co., 401 N. Broac:Street, Philadelphia 8, Pa.


iweep Generatorfrom page 24

erence frequencies)Note how the TV band is covered

vithout the use of bandswitching,liminating a possible source of er-atic operation, and at the same timeeducing the cost of the unit. Forase of operation, the dial is cali-'rated in terms of TV channel num-ters. The sweeping effect is pro-luced as follows :

The fixed frequency oscillator isuned by means of a flat open woundpiral coil (L3), mounted on a bake-ite plate. The plate is mounted onhe chassis close to a unit which isssentially a PM speaker with anetal membrane attached to the cone.[she membrane is free to follow the'oltage variations in the voice coilend will thus vary the frequency ofhe oscillator at a rate determined byhe frequency of the voice coil volt-tge and by an amount (sweepwidth)letermined by the amplitude of theipplied voltage.

The control voltage is tapped fromhe 6.3 -volt filament winding and ap-)lied to the voice coil through R3ind R2. R3 serves to limit the maxi-num voltage applied to the coil atmy setting of R2, and thus prevents:xcessive excursions of the metalnembrane. R2, which is accessible'rom the front panel, then functionsis the sweepwidth control.

The design of the modulator unitillows a sweepwidth of up to 30 Mc,'Mich is more than adequate for usewith any single channel. By usinghe full 30 Mc sweep, it is possiblep compare the relative gain of sev--ral channels. For example, by set-ting the main frequency control tochannel 3 and the sweepwidth tomaximum, the gain of channel 3 canDe compared with that of channels 2and 4, simply by rotating the receiver,elector switch. This procedure isparticularly effective in revealing de-fective r -f coils, switches, etc.

Okffenuation

Another requirement of sweepgenerators is that suitable means ofttenuating the output must be

found. This requirement is met byusing a low value (125 ohms) po-Lentiometer in the cathode of the up-per half of the 12AU7. Since cath-ode follower output is used, no trou-He in coupling to the set under testshould be encountered. Occasionally

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(particularly at high frequencies) ahigh standing wave ratio may be setup in the output cable and result inoscillation and deterioration of theresponse pattern. This may easily beremedied by placing a resistor offrom 50 to 100 ohms across the out-put cable clips, thus matching theimpedance at the clip end of thecable.

A desirable adjunct to an instru-ment of this type is some means ofproviding a sync signal or horizontalsweep voltage to the oscillograph.This sweep must be in sync with thesweep voltage used f Dr frequencymodulation. To accomplish this, the

6.3 -volt filament voltage is againtapped off and applied to the networkconsisting of R18, R17, and C17. Aportion of this voltage is availableat the front panel from a connectormarked 60 CYCLES. R17 providesa phase control adjustment so thatdouble trace patterns resulting fromphase shift may be resolved into asingle response pattern. It must,however, be remembered that phas-ing control may become ineffective ifthere is 60 -cycle hum pickup in theteleset or the 'scope connecting leads.Failure to use shielded test leads forthe oscillograph, neglect of proper

to page 37


Block Diagramfrom page 11

the air. If in every case no soundcomes in, but a picture is received,it is reasonable to assume the troubleis in the sound strip. Obviously, theantenna, front end, video strip, andall other sections except for thesound strip, must be operating sincea picture comes in on all channels.

Design Differences

It should be kept in mind that evensets of the same general type (elec-tro-magnetic, flyback high voltagesystem, standard a -c low voltage sup-ply) may not have exactly the samedesign. For example, a large num-ber of Admiral models follow theblock in Fig. 1 very closely, exceptthat there are two low voltage' sup-plies, one feeding B+ to the tunerand audio strip, and the other pro-viding B+ for the other circuits. IfB+ fails in the first low voltagepower supply, there is a raster, butno sound or picture. If the secondgoes, there is no raster, but there issound. This does not throw out whathas been said about using the blockdiagram in servicing. It merely em-phasizes the point. The block dia-gram of the receiver must be keptin mind, including the connectionsfrom the low voltage supply or sup-plies to the other sections of the set.

Most 7 -inch receivers being soldtoday use static deflection and focus-ing, inter -carrier sound system, andan r -f high voltage power supply.The basic block diagram for thisgroup of receivers follows generallythe block diagram in Fig. 2.

Flywheel Sync from page 21

However, there is one complica-tion. Practically all of the 7 -inchsets, and several larger ones, eventhough designed for a -c operationonly, do not use transformers to en-ergize the tube filaments. Instead,the filaments are hooked up in aseries -parallel circuit across the line.For example, in the Motorola VT 71,the filaments are connected as shownin Fig. 3.

Fig. 3 Filament hook-up in the Motor-ola VT -71. Filaments are hooked up inseries parallel circuit across line

This, apparently, throws the blockdiagram out of the window. Onefilament opening up can knock outseveral other stages in various sec-tions of the reeciver or even all otherstages (if, for instance the filamentof V15 opens) and make the blockdiagram appear to be useless fortroubleshooting purposes. But the

reverse is true. It is only necessar:to keep in mind the servicing situation of the ordinary ac -dc superhetWhen the set is turned on and n(tubes light, an open filament is suspected (since the filaments are it

series). Once all the filaments lighand there still is trouble, the standand procedure is followed : Find th*defective stage, locate the fault:component.

The same approach is used in thetransformerless type of teleset. Thifirst step will be to check if all filaments are lit. If all or some are outan open filament would be suspectec(In Fig. 3, an open r -f choke aballast resistor could also open urone string of filaments). Once th(filaments are lit and there still i,

trouble, the standard servicing approach outlined here is followed.

An increasing number of large:receivers are using the intercarriesound system. With this systemsound is usually not taken off ancfed to the audio strip until after th(video amplifier stage. Therefore,larger number of stages are commorto the video and audio i-f signalWhere there is a raster, but no souncor picture, not only the front end buialso the common stages would besuspected and further checks madethere too.

To sum up : knowledge of theblock diagram of the receiver beingserviced, which includes the arrange-ment of the low voltage supply andthe filaments, is one of the best in-surances for quickly locating the defective section. V

generator tube V12B, any change involtage across R50 will result in achange of frequency in the horizon-tal sweep generator. Thus, if thecontributing voltage of R50 makesthe grid of V12B less negative, thefrequency will be raised; likewise, ifthe contributing voltages make thegrid of V12B more negative, the fre-quency will be lowered. It will beseen that the longer the conductionperiod of tube V12A, the higher willbe the frequency of the blocking os-cillator and of its sawtooth output.

Referring to Fig. 4, curve 2 showsa sync pulse phased so that about 50percent of the horizontal sync pulsewidth is riding on top of waveform

D, while the remainder of the pulse,after point P, falls down into thetrough, making the conducting por-tion have a width which is averagebetween the curves represented by(1) and (3).

If each successive sync pulse fallsin the same phase relation as shownin curve (2), the horizontal holdcontrol, which controls the amount ofcurrent flowing through V12A, is setso that this phase relation does notchange. This would cause the sweepgenerator V12B to run at the samefrequency as that of the incominghorizontal sync pulses. Under thiscondition, if the sweep generatortends to run slower than the incom-ing sync signal, the conduction periodwill be made longer through V12A,

because the pulse will move forwardin relation to waveform D with theresult as shown in curve (1).

It will be noted that the conductingpulse is of greater duration (wider)than in curve (2). Therefore, tubeV12A will conduct for a greater period of time, thus decreasing thenegative potential across R50. Thisgreater conduction period causes tit -sweep generator to speed up until itattains the condition in curve (2).Likewise, if the sweep generator isoperating at too high a frequency,the pulse will advance along the inte-grated sawtooth wave until a largeportion of it falls down into thetrough of waveform D, as shown incurve (3). This conditon results inthe shortening (narrowing) of the


:onducting pulse, causing the f re-luency of the sweep generator to be-educed until the condition in curve(2) is again restored.

The horizontal frequency capacity(C49) forms part of the discharge:ircuit in the grid of the blocking3scillator, V12B. By varying its val-ae, the free -running speed of this3scillator can be adjusted to supple-ment and act as a coarse control forthe horizontal hold control on thefront panel. The free -running speedDf the blocking oscillator is also ad-justed by the inductance variation ofthe blocking oscillator coil T16.

Because this type of a -f -c circuitdepends upon the width of the pulsesabove the cut-off bias of the controltube, it is often called the pulse -widthflywheel sync circuit.

A slight variation of this circuitis worth noting. In some receiversa parallel tuned circuit, consisting ofa variable coil and a fixed capacitor,is used in series with the B+ lead to.he blocking oscillator. This tunedcircuit is inserted at the point markedX in Fig. 3. The resonant frequencyof the tuned circuit is adjusted to15,750 cps. It is shock excited intooscillation by the pulses of plate cur-rent and adds to the sawtooth wave(developed across C50) in properphase to increase the slope of thewave just prior to discharge (retraceportion of sawtooth). This increasein slope affects waveform D, asshown in Fig. 5. The increase in

A

WITHOUT TUNEDCIRCUIT

BWITH TUNED

CIRCUIT

rig. 5 Comparison of a -f -c waveshapes,with and without additional tuned circuitin plate of blocking oscillator.

slope gives greater sensitivity ofcontrol, for it defines more sharplythe shape of the pulse which risesabove the cut-off bias on tube V12A.The net effect is to stabilize the sync,especially in the presence of noise.

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Heethk its are beautiful factory ens'.veered quality service instrumentssupplied unassembled. The buildernot only saves the assembly laborcost but learns a great deal aboutthe construction and features of theinstrument. This knowledge aidsmaterially in the use and mainte-nance of the equipment. Heathkitsare ideal for and used by leadinguniversities and schools throughoutthe United States. Each kit is com-plete with cabinet, 110V 60 cycletransformer (except Handi-Tester),all tubes, coils assembled and cali-brated, panel already printed,chassisall punched, formed and plated.every part supplied. Each kit Is pro-vided with detailed instruction man-ual for assembly and use. Heathkltsprovide the perfect solution to theproblem of affording complete serv-ice equipment one, limited budget.Write for complete catalog.

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"Snap-OnInsulatorsNo other clamp likeit. Snap .. . click . . .and it's on with atight, spring steel grip.Polyethylene inserts fortwin lead.

LIST 10

No. SPT100 (for 1" Mast) ea. $.10No. SPT1.16 (for 1" EMT Conduit) ea. .10No. SPT125 (for 11/4" Mast) ea. .10No. SPT138 (for 11/4" Mast)No. SPT150 (for 11h" Mast)No. SPT175 (for 13/4" Mast)No. SPT178 (for 17/a" Mast)Na. SPT200 (for 2" Mast)

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Increasing Audio OutputTo increase the audio output on

the "30A, B, C, and D Series" Ad-miral TV Chassis for fringe areaoperation, the following changesshould be made:

a. Remove R620 (the 150,000 -ohm resistor) in the 4111 tunerchassis.

b. Increase the values of R219and R220 ratio detector 15,000 -ohmload resistors to 27,000 ohms.

c. Remove the 6AG5 r -f amplifierV101 grid return from the centerarm of R306A contrast control andconnect the junction of R305 andR307. This fixes the grid bias on the6AG5 r -f amplified tube at about .25volts, resulting in more r -f gain.However, if the receiver is locatedin an area where strong signals areto be received as well as weak sig-nals, this change may cause the con-trast control to function improperlyon strong signals. If this happens,fix the bias at a higher negative volt-age by reversing the grid returnfrom the video i-f and the 6AG5 r -famplifier from the original wiringshown in the schematic, by chang-ing the i-f grid return from thejunction of R304 and R305 to themovable arm of the contrast control.The r -f grid return of the 6AG5 r -famplifier should then be changedfrom the contrast control arm tothe junction of R304 and R305.

d. Realign the ratio detectortransformer.

C1046AG5

R.F. AMP.V101

TO HEATERSPIN 7 OF V411

R103

0104

R301

e. Check the 6AU6's in the audiIF. Be sure these are good tube

f. Change the 6K6GT audio ouput tubes to 6V6GT. No circa:change will be needed.

The above changes will improvaudio sensitivity and output, but iis recommended on receivers wherthe complaint is low volume on T'in fringe area operation. It must bremembered that in some areas thTV transmitter is only deviating iiaudio transmission 7 to 10 kc itstead of the allowable 25 kc, whit]will result in low audio volume athe receiver.

If stations are found to be thcause of low TV audio, these changewill improve output but may noproduce more than room volume.

From Admiral Service BulletiiTV -44

Coupling Sweep and MarkerGenerators to Receiver

When using a sweep generatormarker generator, and oscillograplto check the i-f response curves ofa television receiver, it is sometime:difficult to obtain the correct balance between sweep output ancmarker output. This is particular')true when the ranges of the individual attenuators are limited. For bestresults, the amplitude of the applied sweep voltage as well as thatof the marker voltage must be ad-justed to a fairly critical level.

-> to page 38

6AG5IST. VIDEOI.F V301

R302

C302

II1R303

C301-I

c.L 3 01

PH.TELV. RAD

0

R620C304 t 150K SW.602

0 0 03 0 2

R304 R305

CONTRAST

TO TVAUDIO SECTION

F.)

36 JANUARY 1950 RADIO AND TELEVISION MAINTENANCF

iweep Generatorfrom page 33

rounding provisions, etc. are allrobable sources of unsatisfactorysults. Finally, the sweep generator

hould supply an extremely accurategnal for marker pips. One answer; to incorporate into the unit a vari-ble frequency oscillator with excep-onally high frequency stability anddibration. This solution would re -Alt in high expense, which may note necessarily justified.

requency stability

In the Model 360, the problem islet by providing a crystal oscillatorlower half of 12AU7) and a crystalolder mounted on the front panel.'he most obvious procedure is to userystals at the exact frequenciespecified for alignment. However,iis too can be a costly process. Aimple and very effective alternative;to use a crystal of any frequencynd use its harmonics to calibrate atandard r -f signal generator, whichsien becomes the marker generator.'or example, assume that a f requen-y of 21.25 Mc is required for sound-ap alignment. A 5000 kc crystal isvailable. The external r -f generator; set to 20 Mc and checked againstle 4th harmonic of the crystal oscil-stor. If the external generator is outf calibration, it may be realigned.)r the amount of error may be notednd allowed for when setting to theesired frequency. Naturally, a judi-ious choice of crystal is important.t reduces the amount of necessary-iterpolation, and increases the e f-ectiveness of this method.

Aid1111111\AJACENTCHANNELS

CHANNEL 3 _111111PIX CARRI

25.75 MC.ER 11CHANNEL 3

SOUND CARRIER21.25 MC.

CHANNEL 4>IX CARRIER

19.75 MC.

CHANNEL 2"" SOUND CARRIER

27.25 MC.

2 Typical video i-f response curve

Inasmuch as most service organi-ations are equipped with a reason-bly high quality r -f generator, therystal marker becomes a very desir-ble feature, increasing the versatil-ty and utility of the instrument.

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HI-FREQ PROBE

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Industry Presentsfrom page 29

MULTIPLIER PROBEThis probe, known as the "Kilovolt-

er", extends the usefulness of existingd -c voltmeters into the television rangeby effectively adding 5,000 volts tothe scale of readings of conventionalhigh -resistance voltmeters. Fully in-sulated against high TV voltages, thisinstrument is 81/2" long, built withphenolic barrel and clear lucite nosepiece. Three models are available, for50, 100, and 200 microampere metermovements. Insuline Corporation ofAmerica, 3602-35 Ave., Long IslandCity I, N. Y.

ANTENNA ROTATORAntenna rotators have been used

for some time to insure clearer recep-tion. Now Radiart has added its ownmodel, called the Tele-Rotor. It has

375 -degree rotation in either directionat I r.p.m. and positive electrical stopat the end of each rotation. Lights onthe remote control unit indicate theposition of the antenna. The aluminumcast frame of the rotator will take a150 pound load and up to 11/2" diam-eter mast. Power consumption is a low20 watts. Radiart Corporation, Cleve-land, Ohio.

SIGNAL TRACERCalled the Dynatracer, the new

model 777A is a signal tracer whichprovides high amplification, allowingactual gain measurements for receiver;uses meter instead of "magic eye",and traces all disturbance or circuitdefects from antenna to speaker. At-tenuation is 10,000 to I, sensitivity10,000 microvolts for full scale deflec-tion, freq. range appr. 160 Mc. Haslittle hum or noise pickup because oflow 3 mmf input capacity. Radio CityProducts, 152 W. 25 St., N. Y. C.

'ADIO AND TELEVISION MAINTENANCE JANUARY 1950 37

Notebook-0 from page 36

The coupling method shown inthe diagram provides additionalcontrol of the sweep and markervoltages. By sliding the tube shieldup or down on the tube, the capaci-tance between the shield and thetube elements is varied, and thecoupling can be adjusted as desired.Another advantage of this methodis that it is not necessary to makea direct connection to the circuitunder tests; simply slide the tubeshield over the converter tube.

SNUG -FITTING TUBE SHIELD

.005 MFD.

SOLDER

CONVERTERTUBE

TO SWEEPAND MARKERGENERATORS

The system is particularly applic-able with a Mega -Sweep and Mega -

Marker. When using the two piecesof equipment together, the outputof the Mega -Sweep should be con-nected to the Mega -Marker, and thecommon output should be takenfrom the Mega -Marker. Then, byadjusting the attenuators on the twogenerators and sliding the tubeshield up or down on the tube, thecorrect relative voltage amplitudescan be obtained. During the prelim-inary peaking, when only the Mega -Marker is used, the Mega -Sweepoutput cable should be disconnectedfrom the Mega -Marker for best re-sults.

Any tube shield can be used, pro-vided that it fits the tube snugly anddoes not ground to the chassis.

from Westinghouse Service Hints.

Emerson Model 6C448Most frequent complaint on this

model is that it plays on batteries,but will not play on a -c or d -c lines.You will find upon checking thesesets that resistors R16 and R17, 1500and 50 ohms respectively, very oftentend to increase in value. You canvery easily locate these units as theyare mounted upright near the 117Z4rectifier. Make sure to replace theseresistors with 10 watt units of theproper value. This will clear up thetrouble.

Albert LoischDarby, Pa.

the NEW

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model 103-only $4950Now you can buy a genuine Jackson Dy-namic Tube Tester at an amazing lowprice. It's ideal for the serviceman whoneeds an extra tester, for the man juststarting in business, or the ham or ex-perimenter. Look at these specifications.Dynamic* Test Method-First used byJackson test tubes under actual loadconditions.Tests Over 700 Types-Including TVrectifiers and sweep tubes.

TM Reg. U. S. Patent Office

JACKSON ELECTRICALINSTRUMENT COMPANY

Dayton 1, Ohio

Built -In Roll Chart-With free 1 yearreplacement.Quick Set-Up-Combination Push -But-ton and rotary switch selectors.Tests For Shorts-With neon indicator.Many other famous Jackson features!Two More Low -Cost Jackson Instru-mentsl-A new Jackson ChallengerVTVM, and a new Jackson ChallengerRF Oscillator are on the way. Only$49.50 each!

Makers of Jackson "Service -Engi-neered" Test Equipment Tube Testers VTVM's Condenser CheckersAudio Generators RF GeneratorsFM -AM Sweep Generators TelevisionSweep Generators Oscilloscopes.

ASK YOUR DISTRIBUTOR FOR FULL INFORMATION

Service Bench-+ from page 18

in place temporarily, using 1" #8flathead woodscrews, fastenedthrough the braces into the plywood.The upper braces are fastened to theunderside of the shelf.

23. The Masonite panels (#7, 8)should now be held in place tem-porarily, and the small notches in theupper inside corners marked andthen cut. Following this, the testequipment panel braces should bebeveled with a plane until the testequipment panels fit snugly intoplace. This procedure is best doneon a cut and try basis. After thebraces have been properly beveled,they may be mounted permanently inplace. The test equipment panels aremounted with 3/4." #8 nickel platedovalhead woodscrews and washers.The test equipment panels shouldnot be mounted until after the cut-outs for the test equipment have beenmade.

Glueing

Considerably greater strength canbe achieved by glueing all of the sur-faces which come into contact withone another. If there is a possibility

that the bench will have to be moveat some time after assembly, not a;surfaces should be glued, since thbench is so large that it can best bmoved in a semi -knocked down condition. In the event that the bendis to be moved, glue only the following

#23, 26, 28, 32-to sides only.#22-to back only.#25-to shelf only.All parts of the cabinets.The plywood working surf ac

should be covered with a more durable material to improve its appearance and lasting qualities. Materialwhich can be used, in order of preference are : hardwood tongue -ingroove flooring, tempered Masoniteand linoleum. Formica may also lrused, but is quite expensive.

PaintingTwo coats of paint (any color

are sufficient for a utility job to protect the surfaces. The first coacan be thinned out for priming purposes. Where appearance is important, the various wood ends and surfaces should be carefully sanded an,the entire bench covered with a fitscoat of Firzite. 1"

38 JANUARY 1950 RADIO AND TELEVISION MAINTENANC

Documents

ATOM!' RADIO TELEVISION At...and will stand up under the high temperatures, high ripple currents and high voltage surges encountered in TV equipment. Every Sprague TV capacitor rated