Radio and Television Today (Jan-Nov 1941)

ami supply houses io straighten oul "expensive and time-wasting kinks In their lube business." High Gain IF Stage in Farm Sets increased gain and sensitivity is developed in the IF stage Cor certain RCA (arm battery receivers. The circuit of models 25BK and 25BT-3 shown below is similar to other sots in the line which use the same system Cor increasing the IF gain. The primary of the output if transformer is tapped and connected so as to supply a percentage of the output IF voltage back to the screen circuit. Since the tap of the transformer is connected to the B + circuit and therefore grounded through a by-pass capacitor as far as RF currents are concerned, the voltage supplied to the screen grid is 180° out of phase with the voltage across the plate portion of the primary. This voltage on the screen is then in phase with the voltage on the control grid and regeneration builds up the gain of the stage to 120. Usual values for IF stages in battery sets is 80 to 100. Servicemen Hear Sylvania Engineer "Oscillators and Their Applications" was the topic of another radio servicing lecture delivered by Walter R. Jones, Hygrade Sylvania Corp., Commercial Engineer, Emporium, Pa., this time for the Wilkes-Barre, Pa., Radio Servicing Organization. This group is organized under the name of Lucerne County Radio Service Association. Mr. Jones was honored by a very large attendance. In charge of arrangements for the meeting was George Isham, Sylvania Radio tube field representative. Sprague Engineers Save Aluminum News from Sprague Products Co., North Adams, Mass., is that engineers there have worked out an aluminum saving of better than 35 per cent, in the aluminum can housings of condensers. This feat follows the suggestion of the Government that all nondefense uses of alminum be reduced as much as possible, and yet the Sprague experts say that the new small sizes retain all specifications and functional characteristics of the regular product. Catalogs showing these new condensers, and others, are being sent on request Io radio men. Zenith FM Rally in Minneapolis merchandising of the Parts and Service Division of Zenith, in commenting on the future for FM, Mr. Brown said that, "FM is coming fast. Us sensationally beautiful high fidelity lone result has been enthil i astically accepted by an eager public." A lea I ure meeting of a technical nature was held in Minneapolis last month by Reinhard Brothers Co., Zenith distributors for Minnesota. J. E. Brown, chief television and FM engineer for Zenith, spoke on "The Latest Developments in FM and television with servicing side lights." He was assisted by Hal Blakeslee, in charge of Joe Marty with Shure Bros. It has been announced by S. N. Shure that Joe Marty, formerly secretary of the Radio Servicemen of America, is now associated with Shure Brothers, Chicago, designers and manufacturers of microphones, pick-ups, cutters, and other acoustic devices. ______ mgmmammm "Servicing by Signal Substitution" with the combination of Precision Series 920 and Series E-200 will solve your problems with amazing speed and simplicity. ELECTRONOMETER Series 920 E-200 SIGNAL GENERATOR Dynamic Mutual Conductance Type Tube, Battery and Set Tester An indispensable, single compact instrument for both field and service laboratory if 33 AC-DC set testing functions to 3000 Volts, 10 Megohms and 12 Amperes in Provides the individual functions of tube tester, battery tester and multi-range meter ic Permits simplified, rapid check of tubes, voltage, current, resistance, etc., in troublesome stages, quickly localized through "Servicing by Signal Substitution." Series 920P, illustrated above. .. $59.95 Featuring a Simplified Method of Dynamic Receiver Analysis "Servicing by Signal Substitution" Not only an efficient laboratory Signal Generator, but ALSO specifically designed for complete, systematic dynamic signal analysis of every receiver stage from loud speaker to antenna post, regardless of age, make, type. "Servicing by Signal Substitution" provides a new high in simple, rapid localization and determination of receive) troubles with a minimum and economical selection of Basic test equipment. Series E-200, illustrated above. .$39.95 Now in its THIRD printing, and FREE to all purchasers of Series E-200, an illustrated text book describing this amazingly simplified speed approach to receiver adjustment problems, "Servicing by Signal Substitution." Also available at your local distributor or direct from factory at only 35' . See the more than 40 Precision 1942 models at your local distributor. wmm mm StaadaSuC* SEE THEM AT YOUR JOBBER PRECISION APPARATUS COMPANY • 647 KENT AVENUE • BROOKLYN, N. Y. Export Division: 458 Broadway, New York City, U.S.A. Cable Address: Morhanex JULY . 194 1 39