Radio broadcast .. (1922-30)

(Continued from page 587) and a little care on the part of the service- man will be a worthwhile ounce of preven- tion." E. A. SHERMAN, Hastings, Nebraska. SHORT ANTENNAS FOR S-G SETS "An antenna longer than 60 feet with sets using two or more screen-grid tubes is undesirable. After installing an AK-55 with a short antenna it could pick up both coasts any night. A few weeks later the customer came into the store with the complaint that the music was distorted on low volume. Riding up to the house, I noticed an antenna much longer than JEFFERiSOKl .* BELL-RING."'' TRANSFORMER UNE O- Lri i LOAD Fig. 2— A somewhat familiar but always practical method of compensating a consistent line variation. I had installed. Nothing was wrong with the set. I put a condenser in series with the antenna and the distortion cleared up." WALTER STRAUSS, JR., w9ciax, Chicago. Getting Acquainted With AK Defective Resistors: WALTER STRAUSS, who specializes in Atwater-Kents, contri- butes the following: "I am one of those fellows who are loath to drag the set analyzer from the car when an Atwater-Kent set is a bit below par. All the sets below the AK No. 55 employ glass voltage-dividing resistors in the power pack, and if the first a.f. tube is pulled out and put in without a click, it is a reasonably sure sign that the first a.f. resistor is gone. To make sure I put a new a.f. resistor across the terminals and if music comes through, then that's the one." MODEL 55 A serviceman in Eutaw, Alabama, bids us beware of high-voltage shorts: "If the set hums see if the rectifier tube shows a blue glow. If it is dead, look for a burned-out filament. In either case re- move the base cover from the set and in- spect the left-hand or outside plate lead —it may be shorted or arcing to the fila- ment prong on the same side of the set. This will not show up in a continuity test if it is only arcing over. The trouble is caused by rough handling in nearly all instances." SERIES CATHODE RESISTORS An Atwater-Kent dealer in Mount Ver- non, N. Y., keeps the balj rolling: "The last Atwater-Kent we received for servic- ing was a new one that had just arrived from the factory. The set would work all right for a while then it would burst out in loud crashes. We were at a loss as to the trouble, so we sent it back to the fac- tory. They returned it saying nothing was wrong with it. However, the noise was worse than ever. We suspected the first a.f. transformer, but upon replacing it, no improvement was noted. Then we thought the by-pass condenser was punc- tured. However, tests showed nothing wrong here. I happened to be tapping around the set when I hit the series ca- thode resistor (the set was turned on and removed from the cabinet). The crash was heard in the loud speaker. When we re- (Conlinued on page 291) In order to meet the acid test of big theatre sound reproduction requirements, any reproducer must rep- resent the last word in efficiency. The verdict of Mr. E. C. ZRENNER, Sound Engineer of the great Publix theatre interests is overwhelming proof of the satis- faction given by the Wright-DeCoster Reproducer Just as Good for Radio Reproduction The new home model Wright-DeCoster Reproducer is just the same as the theatre model except volume is reduced to fit home requirements. Manufacturers of radio sets who are satisfied with nothing short of the best will install the Wright- DeCoster in their product. Read what Mr. Zrenner says: January I, 1930 WRIGHT-DECOSTER, Inc. 2233 University Avenue, St. Paul, Minn. Gentlemen:—After using several of your Wright-DeCoster speakers and No. 9 horns. I am writing to let you know that they are giving very satisfactory results. Very truly yours, E. C. ZRENNER, Publix Sound Engineer. Write for Complete Details Model 117 Junior Consolette "The Speaker of the Year" WRIGHT-DECOSTER, Inc. 2213 University Ave., St. Paul, Minn. Export Dept.: M. Simons & Son Co., 220 Broadway, New York City Cable Address: Simontrice, New York Are You Experimenting With the New Pentodes? National Co. Inc. also make a full line of power and filament transformers and choke coils. Write us for full information to- day, mentioning Radio Broadcast. Laboratory and home experiments with the new pentode tubes require a reliable source of high voltage. And successful experimentation with the recently announced direct-coupled amplifiers depends on the proper power-supply. The National Velvet-B Power Supplies, in two popular models, give re- liable power tube and accurately adjustable intermediate voltages with minimum hum and a high current output. They are licensed under R. C. A. patents. Priced at $26.50 and $39.50 (Less rectifying tube.) VELVET —B POWER — UNIT NATIONAL CO., INC., Maiden, Mass. Est. <J£> 1914 RADIO BROADCAST FOR MARCH • • 289