C -D PRWIDENCE,R.I.,PLA

"-. C'0 WORCESTER, MASS., PLANT

D BROOKLINE,MASS.,PLANT

C -D SOUTH PLAINFIELD, N J. PLANT

Vol. 16!, CORNELL-DUBILIER ELECTRIC CORP.

Hamilton Boulevard, South Plainfield, N. J.

JANUARY, 1951

POSTMASTER: If undeliverable for any reason.aotify stating reason, on Form 3547 postage for

which is guaranteed.

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The RADIART Corp,CLEVELAND, OHIO, PLANTS

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C0 NEW BEDFORD, MASS ,PLANT

No.1Sec. 34.66 P.L.&R.U. S. POSTAGE

PAID

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PRACTICAL DESIGN OF METER SHUNTSAND MULTIPLIERS

The basis of the multimeter em-ployed in radio and electrical troubleshooting is the simple movable -coil(d'Arsonval) milliammeter or micro -ammeter. Since this current meter hasa characteristic resistance, which isthe resistance of its internal move-ment, it essentially is a d. c. milli -voltmeter, although its scales are grad-uated in current units. The voltagerequired for full-scale deflection isequal to the internal resistance (R.)of the meter multiplied by the full-scale current value (I). Thus, thefamiliar 0-1 d. c. milliammeter em-ployed in many radio circuits has aninternal resistance (in most models) of105 ohms and a full-scale current de-flection of 0.001 ampere. It according-ly is a 105 -millivolt meter, since IR1= 0.001(105) = 0.105 v. = 105 mv.If the reader keeps in mind the fact thatthe basic current meter essentially isa d. c. millivoltmeter, he will be aidedtoward a clearer understanding of thebehavior of multiplier and shunt re-sistors in multimeter circuits.

The basic current meter cannot safelyhandle an applied voltage which ishigher than its full-scale millivoltagcrating. 1 volt, for example, is 9.5times the 105 -millivolt full-scale de-flection of the 0-1 d. c. milliammeterand will damage the meter if applieddirectly to its terminals. The metercan be adapted to give full-scale de-flection at 1 volt, however, by connect-ing a properly proportioned multiplierresistor in series. The multiplier servesto introduce a voltage drop equal tothe applied voltage minus the basicfull-scale voltage deflection of themeter. In the case of the 0-1 milli -ammeter (0.105 volt full-scale deflec-tion) used as a 0-1 voltmeter, the re-quired voltage drop across the multi-plier resistance would have to be equalto 1-0.105, or 0.895 v. This arrange-

ment splits the applied 1 volt into0.895 volt across the multiplier re-sistor and the remaining 0.105 v.across the meter. Similarly; if 100volts were applied to the circuit, themultiplier resistor would have to in-troduce a voltage drop of 99.895 voltsin order that the safe full-scale valueof 0.105 volt would be applied to themeter. The basic d. c. voltmeter cir-cuit, consisting of a current meter inseries with a multiplier resistor, isshown in Figure 1.

D.C. MILLIAMMETEROR

MICROAMMETER

Fig. 1. Basic d. c. voltmeter circuit.

When current values higher than thefull-scale deflection of the basic milli -

ammeter or microammeter are to bemeasured, the meter again is used asa millivoltmeter. But this time thevoltage drop across a resistor carryingthe current of interest is measured.The resistance value is so selected thatthe maximum voltage drop producedwill be equal to the full-scale milli -

voltage deflection of the basic meter.The range of the 0-1 milliammeter maybe increased to 0-10 milliamperes, forexample, by connecting the meter in

JANUARY, 1951 Page 3

parallel with a resistor so chosen invalue that 10 milliamperes flowingthrough the latter produce a voltagedrop of 105 millivolts. Because ofthe connection of the current carryingresistor in parallel with the meter,

Fig. 2. Current meter with shunt toincrease range.

this type of meter resistor is termed ashunt. The basic increased -range directcurrent meter circuit is shown in Fig-ure 2.

The radio- technician also hasadopted the following practical con-cepts of meter resistor operation: Thatthe voltmeter multiplier serves to re-duce the maximum current set up byan applied voltage to the maximumfull-scale current deflection of the in-dicating meter. And that the currentmeter shunt acts as a parallel bypasspath to divert the extra milliamperes,microamperes, or amperes around themeter.

The three preceding paragraphs ex-plain the basic functions of all metermultipliers and shunts. By properchoice of these resistors, a milliam-meter or microammeter m a y beadapted to measure any desired currentand voltage values in excess of thebasic range of the indicating meter. Byswitching multiplier or shunt resistorsof suitable values into the circuit, amulti -range instrument may be ob-tained. The calculation of the re-

quired resistance values for multipliersand shunts is a special application ofOhm's Law.

The experienced technician regardsmultiplier and shunt calculation andapplication as elementary. The lessseasoned worker, however, finds scat-tered information on this subject, aslocated in several textbooks at hisdisposal, somewhat less direct andpractical than he desires. Letters tothe Editors indicate a present demandfor a practical treatment in one articleof meter resistor calculation.

Internal Meter ResistanceBefore discussing the calculation of

meter resistors, it is essential to pointout the importance of internal meterresistance (Rm). This characteristicis of concern since it influences thevalue of any external resistor used toextend the meter range.

As its name implies, meter resistanceis the actual internal resistance of thebasic current meter. In almost allcases, this is the resistance of themeter movement itself, although insome few instances a small series fixedresistor may be installed inside themeter for purposes of standardization.

The meter manufacturer specifies theRm value for each type and range ofd. c. microammeter, milliammeter, andammeter catalogued. But if these fig-ures are not available, the reader maymeasure the meter resistance by themethod explained in the followingparagraph. Never undertake to checka sensitive d. c. meter with an ohm-meter, since the meter under test isapt to be damaged by the ohmmeterbattery.

The simple circuit for checking theinternal resistance of a d. c. milli -ammeter or microammeter is shownin Figure 3. The meter under test isconnected in series with a 11/2 -voltdry cell and a calibrated variable re-sistor, such as a decade box, whichcan be read to the nearest ohm. Start-ing with the highest resistance setting(to prevent damage to the meter),reduce the resistance carefully until

Page 4 THE C -D CAPACITOR

the meter is deflected exactly to one-half of its full-scale reading. Recordthis setting (in ohms) as R2. Then,reduce the resistance setting furtheruntil the meter is deflected exactly toits full-scale reading. Record this re-sistance setting (in ohms) as R1. Theinternal resistance of the meter may becalculated thus: R,,, = R2 - 2R. Thissystem of measurement is based uponthe fact that the external resistancewould have to be doubled in orderto halve the current indicated by themeter if the meter resistance were zero.But since the meter has an internalresistance which is in series with theexternal variable resistor, the resist-ance setting for half -scale deflectionfalls short of twice the full-scale valueby a number of ohms equal to the in-ternal resistance.

By using a decade box as the vari-able resistor, each resistance settingcan be read closely. The calculatedvalue accordingly may be determinedto the nearest ohm. If a decade box

CALIBRATED VARIABLE RESISTOR( See text)

MICROAMrMETEROR MILLIAMMETER

UNDER TEST

11/2 V. DRY CELL

SWITCH

Fig. 3. Circuit for checkingmeter resistance.

is not available, somewhat less ac-curacy will be obtained by substitut-ing a wirewound rheostat as the vari-able resistor. After each setting, onelead of the rheostat must be discon-nected carefully from the calibration

circuit and the resistance setting mea-sured with a resistance bridge or goodohmmeter to obtain the R1 and R:values for calculation.

If Rm values are obtained from man-ufacturer's tables, the reader must con-sult the literature of the builder ofthe particular meter in question. Itmust not be assumed that the instru-ment has the same resistance as one ofthe same current range described insome other manufacturer's data.

Voltmeter MultipliersReferring to Figure 1, the required

value of a multiplier resistor to con-vert a d. c. microammeter or milliam-meter into a d. c. voltmeter of desiredrange may be determined by means ofthe equation:

(1) R ._ (E/I) - RmWhere R is the required multiplier

resistance (ohms)E, the desired full-scale voltage de-

flection (volts)I, the present full-scale current %de-

flection of the meter (amperes)R,,,, the internal resistance of the

meter (ohms)Example. What value of multiplier

resistance will be required to converta 0-1 d. c. milliammeter (internal re-sistance of 105 ohms) to a 0-2 d. c.voltmeter? Here; E = 2, I = 0.001,and Rm = 105. R = (2/0.001) - 105= 2000 - 105 = 1895 ohms.

From Equation (1), it is seen thatthe value R. determines the minimumfull-scale voltage range of the meter.With the meter given in the illustra-tive example, the full-scale deflection(I multiplied by Rm) equals 0.105volt when R= 0 (the condition whenthere is no external multiplier). Itwould be impossible, therefore, to pro-vide a 0.05 -volt range for this meter,since the internal resistance of themeter would have to be 50 ohms.

The internal resistance Rm may beneglected in Equation (1) withoutmaterially affecting the accuracy of thevoltmeter whenever E/I is greater than

JANUARY, 1951 Page 5

100 times Rm. Example: Determinethe multiplier needed to convert a0-100 d. c. microammeter (Rm = 2500ohms) to a 0-1000 d. c. voltmeter. R =(1000/0.0001) - 2500 = 10,000,000- 2500 = 9.997,500 ohms. This is arather odd value of resistance to ob-tain, and since E/I in this case is4000 times Rm, Rm may be neglectedin the calculation and the even E/Ivalue of 10 megohms taken as the re-quired multiplier resistance. The 10-megohm value gives approx. 1/4 volt in-crease in meter deflection at the 1000 -volt full-scale reading, a differencemuch too small to be seen on thisscale.

Voltmeter Input CharacteristicIt is desirable to keep the total re-

sistance of a voltmeter as high as pos-sible, in order to reduce to a minimumthe amount of current drawn by theinstrument from a circuit under test.If the voltmeter resistance is not sev-eral times higher than that of the volt-age source, indications of the instru-ment will be in considerable error.

The most satisfactory voltmeters em-ploy low -range microammeters, so asto use the highest possible values ofmultiplier resistance. The standardmethod of specifying the input char-acteristic of a voltmeter is in terms ofthe amount of multiplier resistance foreach 1 volt of deflection, or so manyohms per volt. This rating may bedetermined by dividing the multiplierresistance value (in ohms) by the full-scale voltage deflection provided bythe multiplier. Thus; a 10,000 -ohmmultiplier with a 0-1 milliammeterprovides a 0 -10 -volt range at 1000ohms per volt, while a 200,000 -ohmmultiplier with a 0-50 microammeterprovides the same 0 -10 -volt range at20,000 ohms per volt. In the lattercase, use of a sensitive microammeterresults in a voltmeter 20 times moreeffective with respect to reduction ofcircuit loading and increase of accu-racy of measurement than the milliam-meter instrument. The ohms -per -voltrating remains constant throughouteach voltage range, being the same

for small voltage deflections as at fullscale.

Extending Rangeof Complete Voltmeter

It often is necessary to extend therange of a voltmeter already built up.The amount of additional multiplierresistance required may be determinedby means of the equation:

(2) R = (NCE) - CEWhere R is the required additional

multiplier resistance (ohms) to be con-nected

C, the ohms -per -volt rating of thevoltmeter

E, the full-scale reading (volts) ofthe meter range which is to be multi-plied.

N, the number by which the presentfull-scale current reading of the meteris to be multiplied.Example. There is available a 0 -1000 -

volt d. c. voltmeter which is rated at20,000 ohms per volt. This meter isto be converted into a 0 -10,000 -voltinstrument for measurement of tele-vision receiver high potentials. Whatvalue of additional resistance will beneeded? Here; N = 10, C = 20,000,and E = 1000. Using Equation (2),R = (10 x 20,000 x 1000) - (20,000 x1000) = (200,000,000) - (20,000,-000) = 180,000,000 ohms = 180megohms.

Current Meter ShuntsReferring to Figure 2, the required

value of a shunt resistor to increase therange of a d. c. microammeter or mil-liammeter may be determined by meansof the equation:

(3) R = Rm/(N-1)Where R is the required shunt re-

sistance (ohms)Rm, the internal resistance of the

meter (ohms)Example. What value of shunt re-sistance will be required to convert a0-1 d. c. milliammeter (Rm of 105ohms) to a 0-500 d. c. milliammeter?Here; the original 1 -milliampere de-flection of the meter is to be multi -

Page 6 THE C -D CAPACITOR

plied by 500, so N = 500, and R. =105. Using- Equation (3), R = 105/(500-1) = 105/499 = 0.210 ohm.

Since shunt resistors have low re-sistance with respect to the internal

Fig. 4. Bridge -rectifier a. c. voltmeter.

resistance of the meter with whichthey are used, they must be mountedas close as practicable to the meterterminals and must be connected tothe latter by means of heavy, shortleads to avoid extraneous resistance.When shunts are switched into thecircuit in a multirange instrument,the selector switch must have tight -engaging, heavy contacts, in order toreduce resistance from this source.

While it is desirable to keep thetotal input resistance of a voltmeteras high as possible, the opposite istrue of the current meter. A microam-meter, milliammeter, or ammeter musthave as low input resistance as pos-sible, otherwise the instrument willintroduce an objectionable voltagedrop in the circuit into which it isinserted.

The more sensitive (lower -range)current meters have the higher inter-val resistance values. Before under-taking measurements with such instru-ments the technician must determineif the instrument resistance may beinserted into the circuit under testwithout upsetting circuit operation.

The A. C. VoltmeterFigures 4 and 5 show simple recti-

fier -type a. c. voltmeter circuits. Itwill be noted that the only point ofdifference between these circuits andthose of d. c. voltmeters is the in-clusion of a rectifier to drive the basicd. c. milliammeter.

In Figure 4, a full -wave rectifier isemployed. While the common meterrectifier usually is of the copper oxidetype, each of the four arms of thebridge might also be diode tube sec-tions, germanium crystal diodes, orspecial subminiature selenium units.

In Figure 5, half -wave rectification isemployed. When the upper a. c. in-put terminal goes positive; currentflows in the direction of the solidarrows through multiplier resistor R,rectifier diode RECT,, and the milliam-meter which is deflected up -scale.When the lower a. c. input teminalis positive; a small current ordinarilywould flow through the meter andRECTI, causing a small down -scale de-flection of the meter. This currentwould be small because rectifier RECTInow presents its cathode to the posi-

Fig. 5. Half -wave -rectifier a. c. voltmeter.

tive potential and accordingly is back -connected and appears as a high re-sistance. Passage of this reverse cur-rent through the meter is preventedby rectifier diode RECTI which is con -

JANUARY, 1951 Page 7

netted so that its anode is presentedto the positive potential. RECT2 thusappears as a low resistance, and cur-rent is detoured around the meter cir-cuit in the direction indicated by thedotted arrows.

In rectifier circuits of the type shownhere, the milliammeter deflection isproportional to the average value ofthe applied alternating voltage. Thedeflection therefore is somewhat less(usually about 10 per cent lower) thanit would be for the same value of ap-plied direct current. For this reason,multiplier R must be higher thanwould be required in a d. c. volt-meter circuit. The actual value of themultiplier depends upon individualcharacteristics of both the rectifier andmilliammeter: There is no simple andfoolproof method which we can rec-ommend for calculating the requiredvalue of a multiplier for the rectifier-type a. c. voltmeter. The best practicalscheme is to connect a calibrated vari-able resistor, such as a decade box, inthe multiplier position, apply the de-sired full-scale a. c. input voltage tothe a. c. input terminals, and adjustthe resistor for full-scale deflection ofthe milliammeter. A multiplier thenmay be made up, using fixed resistorshaving. a total resistance correspond-ing to the setting of the test resistor.If a decade box is not available, awirewound rheostat may be used. Af-ter the proper setting has been made,the rheostat must be removed fromthe circuit and its resistance settingmeasured with a good resistance bridgeor ohmmeter.

A special a. c. voltage scale mustbe provided for the milliammeter,since response of the circuit is notlinear. The non -linearity of the recti-fier increases at low voltages, requir-ing that a separate scale be preparedfor full-scale deflections such as 1, 2,2.5, and 5 volts. A 10 -volt scale willserve also for 100 and 1000 volts, a20 -volt scale for 250 and 2500 volts,etc., etc.

Page 8

Specifications of Meter ResistorsVoltmeter Multipliers. Highest accu-racy and best long-term stability willbe obtained with wirewound resistors.When odd multiplier resistor valuesare required, they may be made upby connecting in series several. resistorshaving values which total the requiredmultiplier value.

Precision wirewound resistors, de-signed for instrument applications, areavailable with accuracies of 1, 1/2,

and 1/10 per cent. These componentsare non -inductive, possess a good tem-perature - resistance coefficient, andshould be used whenever possible.Current Meter Shunts. The low -resist-ance units required as current shuntsordinarily are not as readily availableas manufactured items as are multi-plier resistors. We refer, of course, tothe shunts required for milliammetersin radio -electronic test gear. In gen-eral, shunts must be made by thetechnician.

Manganin wire should be employed,since this material has an excellenttemperature -resistance coefficient notpossessed by some of the other resist-ance wire alloys.

The wire may be cut to the properlength to give a desired resistancevalue, as determined by measurementswith a d. c. resistance bridge. Theshunt is completed by winding thewire on an insulating bobbin or cardor, if the wire is short enough, simplycoiling it without a supporting formand soldering its ends to terminals.

Final adjustment of the shunt mustbe made with this resistor connectedto the meter. A standard current meter,of known accuracy, may be used forcalibration. For this reason, it is ad-visable to make the shunt with a littlemore than the calculated value of re-sistance. The excess resistance, as de-termined by calibration of the com-pleted instrument, then may be prunedaway by clipping off a fraction of aninch of the resistance wire at a time.

THE C -D CAPACITOR

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A Free Market -Place for Buyers, Sellers, and Swappers.These advertisements are listed FREE of charge to C -D readers so if there is any-

thing you would like to buy or sell, if you wish to obtain a position or if you have aposition to offer to C -D readers, just send in your ad.

These columns are open only to those who have a legitimate WANTED, SELL, orSWAP proposition to offer. The Cornell-Dubilier Electric Corp. reserves the right toedit advertisements submitted, and to refuse to run any which may be considered un-suitable. We shall endeavor to restrict the ads to legitimate offers but cannot assumeany responsibility for the transaction involved.

Please limit your ad to a maximum of 40 words, including name and address.Advertisements will be run as promptly as space limitations permit.

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1Z>wwi:iw."+ w CI> IZ

"MANY" THANKS

Both our organization andmyself take this opportunity tothank our many friends andreaders for the nice Christmasgreetings with messages of ap-preciation of the helpfulness andservice our little publication,The C -D Capacitor, has been tothem. Cards of all varietiesfrom servicemen, radio ama-teurs, engineers, students andradio tradesmen came fromthose in Brooklyn to Bombay ex-tending greetings this holidayseason. Many, many thanks.

Cordially yours,William G. Many, Editor,

The C -D Capacitor.

w r Zi; r..`3 . > r,;, tC:

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FOR SALE-BC412 oscilloscope, completelyconverted from standard conversion blue-print, print included. Scope will not beshipped. Without tubes, $25 - withtubes, $30. Also Dumont No. 168 5"scope, $25. William Henshaw, 46 FrontSt., Tarrytown, N. Y.

Page 10 THE C -D CAPACITOR

FOR SALE-Beam rotator, consisting ofgear box, motor and selsyn indicators,$10; 1,000 volt plate power supply, $10.Must be picked up, will not ship. P. J.Faulkner, 136-05 Sanford Avenue, Flush-ing, L. I., N. Y.

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SELL OR TRADE-Hickok model 610 univer-sal television alignment sig. gen., ex-cellent, $100 cash. Or trade for RCA630TS TV receiver. Mellott's Radio Sales -Service, 6419 Cherry Ave., Long Beach 5,Calif.

WANTED-An AM -FM crystal controlledsig. gen., Simpson, Triplett, or Hickok.Give model number, length of time used,exact condition, and lowest cash price.Mercury Radio Service, 439 South Wa-bash Ave., Chicago 16, Ill.

FOR SALE-Television cabinet (for tablemodel 10" Fada TTV30 or 799 chassis)fits RCA 630 type chassis. Excellent,walnut, make offer. Raymond Conover,Stone Ridge, N. Y.

FOR SALE-Television for Radiomen byEdward M. Noll, $4. Les Hague, 2804 -33rd Ave., Astoria, L. I. C. 6, N. Y.

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FOR SALE-Hickok model 203 volt, ohm,capacity milleammeter, $75; 2 Vomaxmodel 900, $25. In excellent condition.Phil Maggio, 718 Eagle St., Utica, N. Y.

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SALE OR SWAP-All nine transformersfrom BC -610-E and three chokes L1, allin good condition. Will sell or swap forLysco model 600, Hunter Band -It 20B, ornewer model Meissner signal shifter.R. O. Schramm, Route 2, Portland, Ind.

FOR SALE-Instructograph code practicemachine, spring motor, complete set of(wire) tapes, instruction book, and Sig-nal -Electric telegraph set M-110. In ex-cellent condition, $25. George Luellman,300 Milledge Circle, Athens, Georgia.

FOR SALE-Gardiner automatic code tapesender with 20 code practice lessons.3 months old. A $24 value for $15. $3down, balance C.O.D. D. Ridgley, 1345Porlier St., Green Bay, Wis.

WANTED-Technical Manual (not dia-gram) on BC -788 and I-152 altimeter andindicator, and APN-4 Loran. Very ur-gently needed. Will pay cash. S. Bal-sera, Jr., 25 - 1004 Vedado, Havana,Cuba.

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FOR SALE-Hammarlund HQ 129-X, $140;Meissner signal shifter, $50; originalVibroplex Bug, $10. All perfect cond.,f.o.b. Bob Childress, 1205 ChamberlainAve., Chattanooga, Tennessee.

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FOR SALE-Precision multitester No. 830,and 6 volt "A" bat. eliminator, $12 ea.;vac. tube V.M. with 500 microammeter,a.c.-d.c., $8; Supreme Autom. Lab., No.385, good cond., $35. Will trade all forSupreme 504B. W. F. Onder, R 1, Box330, Arnold, Mo.

WANTED-Rider's Manuals, vol. 1 to date.Advise on volumes you have and price.James E. Kilroy, 924 Stock St., Pitts-burgh 7, Pa.

FOR SALE-RCA 5TP4 projection tube ingood condition. A bargain, $9. H. Bergh,1583 E. 96th St., Brooklyn 36, N. Y.

JANUARY, 1951 Page 11

FOR SALE-Hickok signal generator, mod-el 288X; Rider Manuals vols. 8, 10, 11,12, 13. Both excellent cond., Best offer.Herbert Dregalla, 915 Spring Rd., Cleve-land 9, Ohio.

FOR SALE-Back copies QST, excellentcondition. 1943 - 44 - 46 complete, 45except April, also 42 June and Dec. only,47 Jan. and Feb. E. E. Ross, 446 RossAve., Pittsburgh 21, Pa.

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WANTED-A 5" or 7" TV set. Willing topay a reasonable price. Phil Kantrowitz,203 East 174 St., Bronx 57, N. Y. C.

FOR SALE-Hammarlund 4-20 transmitterand modulator 80, 40, 20 and 10 metercoils with built in VFO. Will ship pre-paid. Price, $90. Edward A. Spacek,311 East 70 St., New York 21, N. Y.

FOR SALE OR TRADE-ART-13 (verygood); BC779-B (beat up shape); K.W.power supply and final parts; TCS-11and dynamotor; BC344-D (excellent).Will trade for garden tractor. B. Arm-strong, 18425 4th S. W., Seattle, Wash.

FOR SALE-Vomax VTVM, excellent cond.,only $35. William Harsh, 2001 ParkerSt., Berkeley 4, California.

FOR SALE-Sylvania tube tester; Meis-sner Anaylst; Jackson sig. gen.; SprageTel -O -Mike. All complete, in excellentcond., $190, or will sell separate. JohnAllen, 2820 Louisiana, Longview, Wash.

WANTED-BC222 heterodyne freq. meterin perfect order, complete with calibra-tion book. Must be reasonably priced.William H. Smith, 115 Eastern Ave., Bell-more, L. I., N. Y.

FOR SALE-Simpson 479 TV -FM sweepgenerator, very good cond.; vol 14 andvol. 2 Riders TV. Best offer, cash only.C. Osiecki, 65 Vine St., Ansonia, Conn.

WANTED-Rider's Manuals, 11, 16, 17, 19,and 20. State vol. No., price, and cond.J. O. Basham, Altamont, Covington, Va.

FOR SALE-S40A Hallicrafters, perfect con-dition, with or without panel mountedS meter, phono input jack, and externalspeaker jack. Best offer over $60 f.o.b.R. E. Franklin, 239 East Fourth Ave.,Roselle, N. J.

FOR SALE-HT-17 transmitter (Hallicrafter)with all coils, never been used, $35;S41 -G receiver, good condition, $22.Louis De Meo, 113 University Pl., N. Y.

FOR SALE-Rider Manuals, vols. 8 to 17inclusive, in excellent condition, aboutone year old, used very little. Will takeconsiderably less than cost, make offer.H. F. Albee, 377 Ingleside Ave., Dayton4, Ohio.

WANTED-Gonset 3-30 converter. GoodVOM. G. Thompson, 830 Kains Ave.,San Bruno, Calif.

FOR SALE-Fourteen volumes Riders Man-uals, 1 to 14 inclusive, with index. Con-dition good to excellent. $90 f.o.b.Chauncey Coston, Rt. 3, Box 25, Ho-quiam, Wash.

FOR SALE OR TRADE-Cameras for newcondition television service equipment.Also have radios, transmitters, scopes,etc. K. H. Stelle, 3619 W. 102nd St.,Inglewood, Calif.

TRADE OR SELL-Japanese voltmeter, verysensitive, 6" meter, in well constructedcase. Want used television set or S-38receiver. Paul M. Jenks, Jr., 317 N. Nel-son, Pampa, Texas.

WANTED-Code machine, withor without tapes. Will pay cash. Statetype, condition, price. L. H. Kephart,214 W. Lincoln St., Tucson, Arizona.

FOR SALE-Eico scope, 5", model 400,perfect condition, $35. Evancich Radioand TV, 9528 Commercial Ave., Chicago17, Ill.

WANTED -300 or 500 watt gas generator.Vernon Blaine, Gary, S. D.

FOR SALE-Wilcox Gay portable profes-sional recorder, used less than 2 hours.Sacrificing for $100 for a quick sale.Perfect condition. Howard R. Klauer,639 N. Central Park Ave., Chicago 24,Illinois.

WANTED-Portable a.c. and d.c. radio.Also target gun. A. E. Levriett, Box 3542,Sta. F, Jacksonville, Fla.

WANTED-Rider vols. 15 and 18. Stateprice. Southend Radio Service, 2346South Washington, Wichita 9, Kansas.

FOR SALE-General Industries single playrecorder play -back, complete with 12watt amplifier, carrying case, used little,excellent condition, $30. Tuck RadioService, Point of Rocks, Md.

Page 12 THE C -D CAPACITOR

FOR SALE OR TRADE-8mm projector andcamera, imported Jap and German fieldglasses, tubes, and other assorted radiostuff. Want used TV receiver in goodcondition. D. B. Hoffman, 960 E. 12thSt., Brooklyn 30, N. Y.

FOR SALE-NRI tester (VTVM) batt. oper-ated, manual included. Needs 45V" batt.,$5 plus express or postage. H. G. Cool-ing, 428 Formwalt S. W., Atlanta, Ga.

SELL OR TRADE -7" TV set (works poor-ly), and Mark II set converted to a.c.(excellent condition). Want cash orfirearms. P. H. Trautwein, 40-25 206 St.,Bayside, N. Y.

FOR SALE-Presto K-8 professional typerecorder, crystal mike, several blanks,$200, or best offer. Gerard J. Ward,12608 Watterson Ave., Cleveland 5, Ohio.

FOR SALE OR TRADE-American made32 cal. revolver, includes ammunitionand holster, perfect condition. Wanttube checker with roll chart or AM sig.gen. L. D. Wilder, 826 St. Charles,New Orleans, La.

FOR SALE-Precision 844-P volt -ohm -milli -ammeter, 34 ranges a.c.-d.c., in hard-wood portable case with instructions,batteries, standard test leads and HVtest leads, excellent, $24. Seymour Sin-uk, 1366 Clay Ave., New York 56, N. Y.

WANTED-RCA battery VoltOhmyst, mod-el WX-65A, in complete operating con-dition, with test leads. Will pay rea-sonable cash, or have Hickok 1000 ohm/volt multimeter with 41/2" face as par-tial trade. George F. Steeg, 118 Sara-toga Ave., Waterford, N. Y.

FOR SALE-Well stocked radio shop. Rent$40 per month with heat, mgr. passedaway, sell for $1,500 cash. Harry'sRadio Shop, 7019 Indiana Ave., Cleve-land 5, Ohio.

WANTED-Rider Manuals vols. 15-19 in-clusive, in good condition. State price.Black Radio Service, 1000 So. 10th, Bur-lington, Iowa.

FOR SALE-Copy of Nilson and Hornung"Practical Radio Communication," per-fect condition, $5. Leon Medler, 2109Daly Ave., Bronx 60, N. Y.

WANTED-BC624 (SCR 522) converted for2 meters or otherwise. State price anddetails. Have excellent Webster 78 rpmchanger if exchange is wanted. GeorgeW. Harrold, 1907 So. Park Ave., HaddonHeights, N. J.

WANTED-Precision E-400 TV sig. gen.Also Sams Photo -facts 51 to 90 Statecondition and price. Elmer E. Ash, 431N. Milwaukee St., Port Washington,Wis.

FOR SALE-McMurdo - Silver receiver802 in good condition, all tubes, all coils,80 to 6 meters, $22. H. I. Griffiths, 39-8265 Place, Woodside, L. I., N. Y.

WANTED-Sig. gen., tube tester, VOM, atreasonable price. John Beechan, Box 97,Cairnbrook, Pa.

FOR SALE-Amplifier, 18 watt output,Stancor transformers, highest qualityparts throughout, $22.50 prepaid. V. R.Hein, 418 Gregory, Rockford, Ill.

FOR SALE-Meissner FM receptor, model9-1047A, 8 tubes, 41.2 - 50.4 MC, perfectcondition. Also Weller dual heat solder-ing gun, 135 watt -100 watt, very good.J. Lipiner, 1032 Rutland Road, Brooklyn12, N. Y.

FOR SALE-NC-173, excellent cond. withmatching speaker, $130. Will deliver inBoston and vicinity. S. Swetzoff, 149Intervale St., Boston 21, Mass.

SWAP-Deluxe Blue Racer Vibroplex bugin carrying case for used Pilot FM tunerin good condition. R. T. Beck, 1305Jefferson, Racine, Wis.

FOR SALE OR TRADE-Hallicrafters S2ORin very good condition. Make an offer,or what have you to trade? Carl F.Pietschner, 1045 Mary's Dr., Wichita 12,Kansas.

FOR SALE-RCA Rider Chanalyst, excel-lent condition, $85. Also Rider Manualsin A-1 condition at $10 ea. Carrs TVCenter, 15-17 Kelley Square, Worcester4, Mass.

FOR SALE-Brush BK-401 tape recorder,top condition, new motor, 5 new tubes,$100. Brush and Scotch brand tapeswith operas, etc., $2 ea. H. Heller,12326 Fairport Ave., Cleveland 8, Ohio.

WANTED-Set of instructions for Hickoksignal generator model No. 15 andHickok volt - ohm - milliammeter model202B. Jennings Radio Service, 230 Wash-ington Ave., Covington, Va.

FOR SALE-R.C.P. model 450A portablemult. meter, $20; Astatic JT-30 crystalmike, $6; Kingston battery charger 6V,$6; Burgess electric sprayer, $5. All inexcellent condition. Lewis Mascara, 197McKay Ave., Huntington Station, L. I.,N. Y.

JANUARY, 1951 Page 13

WANTED -2 meter transmitter and receivercomplete, prefer SCR522. State condition,description, and price. Edmund Bedat,1601 E. Cheltenham Ave., Phila. 24, Pa.

WANTED -Amateur mobile equip. Trans.and receiver converters. Also vibratoror Dynamotor power supply. Interestedin good equipment. E. Harris, 5815 N.Wayne Ave., Chicago 40, Illinois.

WANTED -Two walkie talkies, used ornew, or similar equipment. Specify freq.Ryan's Radio and TV, 15 Lincoln Ave.,Havertown, Pa.

FOR SALE-Meissner 8C FM tuner andcabinet, excellent, $25; Webster 56changer with base, $10; RCA 20W hi. fi.amplifier, $25. R. C. Spangler, Marietta,Pa.

WANTED -Will buy transmitting, special-purpose and receiving type tubes. Willswap. B. N. Gensler, 136 Iiberty St.,New York 6, N. Y.

FOR SALE-Hallicrafter 36A, $100; SCR522 rec. and trans. with tubes, $20.Peter Dal Corobbo, 10441 Corliss Ave.,Pullman 8836, Chicago 28, Ill.

TRADE -BC -348-Q, converted tq a.c. Wantpress type camera, Graphic preferred.Elvin L. Holley, Box 336, Vaughn, NewMexico.

FOR SALE -Very good National "57,"with new separate "5" unit. Also G. E.electric unimeter radio clock. Frank E.Wooley, Apt. 22G, 415 Union Ave.,Irvington, New Jersey.

FOR SALE-RME-45 receiver and BC -375-ETransmitter with units and dynamotor.Equipment in good condition. H. Strac-cio, 569 N. Main St., Mansfield, Mass.

TRADE-G.E. 110V d.c. input rotary con-verter to two phase 80v or single phase115V a.c. Want condenser analyzer orwhat have you? Richard Schneider,192 Willoughby Ave., Brooklyn 5, N. Y.

TRADE -Excellent Heath signal tracer forPilot FM tuner in very good condition.J. W. Landon, Wayne, W. Va.

FOR SALE OR TRADE -Kodak 35, RF,f3.5 coated lens, Weston Master II, flashunit, carrying cases, etc. Want highgrade test equipment. Al B. Werhan,Box 142, Manlius, N. Y.

WANTED-7EP4 C.R. tube. Must be ingood condition. Brace Radio, 32-09 44 St.,L. I. C. 3, N. Y.

SELL OR TRADE -Silver condenser testermodel 904, $35; Philco Junior scope mod-el 7019, $35. Or will trade one instru-ment for a solar Exam-Eter CF -1-60.Arthur Wood, 93 Ralph Ave., Brooklyn21, N. Y.

FOR SALE -Tubes and ballasts from 1.4Vto 117V, list $44.95, entire lot prepaid,$12.50; 6 tube underdash auto set, $12.50;Astatic xtal mike, $6.50; Everything plusodd lot parts prepaid, $30. Ellis RadioService, 421 Grand St.; Vermilion, Ohio.

FOR SALE -Excellent Revere tape recorder,$125. Also excellent Gonset 10-11 meterconverter, $27.50. Milton Kalashian, 2Congress St., Newburyport, Mass.

FOR SALE OR TRADE -Wilcox Gay homerecorder, has phono, radio PA system,plus mike, originally $175, case shop-worn. Also 16mm movie camera, $10,and projector, $25. J. Madden, 412 Co-lumbus Ave., Tuckahoe 7, N. Y.

FOR SALE -Precision E-200 C sig. gen.,$55; Rider Manual 15, $12; Ghirardi RadioServicing, Audels Radioman's Guide,Supreme Radio Diagrams 1926-38, threebooks, $8. All items near perfect. JohnH. Schaeppner, 615 East 7th St., Brook-lyn 18, N. Y.

FOR SALE -NC -57 in A-1 condition, $65.James L. Tift, 577 So. Beech St., Man-chester, N. H.

FOR SALE OR TRADE -Good disc record-ing and playback unit; Remington type-writer; sig. gen.; CREI radio engineer-ing course; tube tester; many otheritems. E. G. Bartlett, Box 86, Atlanta,Missouri.

FOR SALE -Model 576 Supreme sig. gen.;Triplett model 2413 tube tester; 45 asst.condensers, 35 asst. tubes; other smallarticles; going out of business, $85 JamesH. Barker, Mt. Holly, N. C.

WANTED -TV set in working condition.Have NRI tracer, Heath VTVM, BasicScope kit, CRT Voltage supply, anddraftsmen's tools. Carl Moore, Jr., 432Lookout St., Warren, Pa.

WANTED TO BUY-BC348, BC312, BC788,BC794, CW-3, SCR522, F-3, APS13, Super -Pro receiver, ARC -3. Please state quan-tity, condition and price. Alfred Living-stone, 12-01 Ellis Ave., Fair Lawn, N. J.

FOR SALE -National short wave three withthree sets of coils and power pack. Alsohave radio parts, books on drawing,painting, record changer with motor, jigsaw, etc. John Haynes, Doe Run, Mo.

Page 14 THE C -D CAPACITOR

only

TINY

MIKEceramics

The vast resources of Cornell-Dubilier"know-how" have been concentratedin the new TINY MIKE ceramic disccapacitor, resulting in a product thathas made the C -D reputationworld-famous for more than 40 years.

That's why only C -D TINYMIKES*combine all these features:

Lowest possible inductance, due tocarefully selected body shape, andparallel leads, resulting in shortestpossible connections.

Reduced eddy current losses andincreased Q, due to accurate positioningof the high -purity silver electrodes.Uniform ceramic bodies, insure the sameelectrical characteristics in each lotof capacitors.The bond attained by the use of thenewly -designed wire lead has greaterstrength than all previous designs.Capacity in mmfd. clearly marked oneach capacitor.

1910 1951

G/VEy° u

qzlFSFFs."v

TINYMIKES now available in aServiceman's replacement assortment(containing 10 ceramics in thecapacities most -needed for replace-ment purposes), or in packages of 10of any one capacity. Values rangefrom 50 to 150 mmfd. ± 20% and 500 to10,000 mmfd., guaranteed minimumcapacity. See classified phone bookfor nearest jobber.CORNELL-DUBILIER ELECTRIC CORPORATIONSouth Plainfield, New Jersey

CORNELL-DUBILIERCAPACITORS

BEST BY FIELD TEST

Other plants: New Bedford, Worcester and Cambridge, Mass.; Providence, R. 1.;Indianapolis, Ind., and subsidiary, The Radiart Corp., Cleveland, O.

MORE CD's than

any other!It's no accident that there are more Cornell-

Dubilier A -C electrolytic motor -starting ca-

pacitors in the field than any other make!

C -D has earnec this leadership by exceed-

ing your needs for consistent dependability.

HERE ARE A FEW TYPICAL C -D PLUS FEATURIES BUILT INTOTHE TYPE ETB ELECTROLYTIC CAPACITOR:

* Dual -Type Terminals - for soldered or screwdriverconnections.

* Safety -Plug End Cap - prevents motor damage fromexcessive internal pressure due to overload.

* Special Foil Formation Process - results n lowpower factor.

* Complete Customer Acceptance and Confidence in theC -D Label - guarantee of continued dependability.All adding up to more profit for you!

Catalog 163, your tree motor -starting capacitor manual and catalog,now available at your local jobber. Write for his name today. Cornell-Dubilier Electric Corp., South Plainfield, N. J.

Printed in U.S.A