Radio Broadcast (May 1929-Apr 1930)

RADIO BROADCAST "The same method may be utilized to ascertain the ratio of an unmarked a.f . transformer. Connect line across the secondary and read the voltage across primary. "It is always good policy to test for short circuit or grounding before proceeding." John H. Steureb, E. E., Rockville Centre, N. Y. A Non-Metallic Screw Driver The serviceman will often find use for a non-metallic screw driver, particularly in adjusting and aligning tuning condensers. E. G. Cotton, manager of the Quick Radio PLASTIC WOOD HANDLE, Service, of Norman, Oklahoma, suggests molding a handle of plastic wood and inserting a thin piece of steel in one end before the wood sets. The idea is sketched in Fig. 2. Simple Test Prods "In making test prods I take two sixinch pieces of bus wire, round or square, solder same to the desired length of Belden Colorubber wire, and then slip a length of spaghetti over the bus. Cut the spaghetti so as to expose about an eighth of an inch of bus wire and, of course, long enough to cover the remainder of the bus wire and the soldered joint. Fasten the spaghetti to the insulation of the test wire with cement or by tying." H. W. Hudelson, Radio, Auto Service and Merchandise, Vandalia, Mo. Calibrated Capacity Meter R. W. Shelton, specializing in radio service, of Paducah, Ky., suggests a somewhat unusual addition to the serviceman's test equipment in the way of a simple calibrated capacity meter. The apparatus he describes is effective in measuring capacities between 0.1 and 12 mfd., and should prove most useful in determining the capacities of those filter and by-pass condensers that shed their labels like a duck does water. "The calculation of capacity may be expressed in the following formula: C = I X 1000 2nfE where C is the capacity in microfarads, I is the current in milliamperes, E is the voltage, and f the frequency in cycles. "The number 100 readily lends itself to calculations, and, as it is may be obtained easily by dropping the conventional 110volt house supply through a suitable resistor, 100 volts at 60 cycles will be used in making our measurements. "The circuit is shown in Fig. 3. The milliammeter and the voltmeter are a.c. instruments having respective ranges of from zero to 500 mA. and from zero to 150 volts. The resistor, R, may be any convenient value that will drop the line voltage to 100 volts. A high-range power Clarostat is ideal for this purpose. "To measure the value of a condenser, the first step is to ascertain that the con(Continued on page 231) AmerJran TRADE MARK REG.U.S.PAT.OFF^b* Type AF 8 Audio Transformer—Either 1st or 2nd stage audio, turn ratio il/2-List Price $6.00 I « nr. T.O" , _ • I I 0 * $ " . . I * AmerTran ABC Hi-Power Box — 500 volts DC plate voltage, current up to 110 ma; AC filament current for all tubes for any set. Adjustable bias voltages for all tubes.Price, east of Rockies — less tubes — $130.00. mm w ''Complete 2 stage audio amplifier with first stage AmerTran De Luxe forUX 227 AC and second stage AmerTran Push-Pull for two 171 or 210 power tubes. Operates with 450 volt AmerTran Hi-Power Box. Price east of Rockies— less tubes— $80.00. Amer Tran D e Luxe Audio Transformer — List Price $10.00. Type 151 — Between one input and two 'output tubesList Price $15.00 AmerTran Poiver Transformer Type PF-245A — List Price $22.00 *Liccnsed under parents of the Radio Corporation of America and associared companies for radio, amateur, experimental and broadcast reception. Quality RADIO PRODUCTS AmerTran Audio and Power Transformers and Amplifiers are designed for those who truly appreciate fine quality in radio reception. Weakness in the audio system in many receiving sets results in failure to deliver full richness of tone along the entire scale. AmerTran Radio Products perfect the audio system and reproduce music and the speaking voice in true tone (without distortion at any volume) just as broadcast in the studio. FOR DETAILED INFORMATION WRITE FOR THE FOLLOWING BULLETINS: BULLETIN 1084 AmerTran DeLuxe Audio Transformer BULLETIN 1087 AmerTran Audio Transformer Type AF-8 BULLETIN 1088 AmerTran PowerTransformerType PF245 A BULLETIN 1076-A AmerTran Hi-Power Box Type 2 1-D BULLETIN 1075-A AmerTran Push-Pull Amplifier Type 2 -AP BULLETIN 1065 The Complete AmerTran Line. AmerTran Quality Radio Products are sold by all good dealers, or direct if they cannot supply you. AMERICAN TRANSFORMER COMPANY "Transformer builders for o-ver 2y years 172 Emmet Street, Newark, N. J„ AMERICAN TRANSFORMER COMPANY, 172 Emmet St.,Newark,N.J. R.B. z-; Please send me the following Bulletins (Check ( v) those you want). Bulletin 1084 ( ) ; 1087 ( ) ; 1088 ( ); 1076-A ( ); 1075-A ( ); 1065 ( ). Name Street and No. Town .....State. • FEBRUARY 1930 • • 229