Radio Broadcast (May 1929-Apr 1930)

Plugs Schematic diagram of Mr. Howard's test set. is to solder a piece of No. 22 hard-drawn brass wire across all of the rotary plates and ground the wire to the adjustment nut on the left end of the condenser shaft. The wire should be fastened under this adjustment nut first and then wrapped around the shaft once, forming a spiral, or pig-tail, before it is extended across and soldered to each of the rotary plate gangs. "This will generally improve the operation of the set about 30 or 40 per cent. "Another thing about the model 11-e and 14-e Zenith that needs a lot of attention is the balancing of the condensers. This, of course, should be done with a good oscillator. I find that the best volume and tone quality may be obtained by setting the second and third r.f. stages approximately two meters lower, and the detector stage) approximately three meters higher, (at 300 meters) than the antenna stage. If the four condensers are all set alike it will make the set so sharp that the tone quality will be affected materially." A. D. Woodyatt, Marshfield, Ore. An unusual case of distortion: "The writer recently ran into a case of distortion which is, he believes, a bit out of the ordinary. The owner of a Majestic Model 70 receiver complained of oscillation and distortion on all frequencies and a check of the set disclosed the fact that the r.f. plate voltages were too high and the plate voltage at the output was too low. The set was removed from the cabinet, checked carefully, and found o. k. as was the powerpack. The dynamic loud speaker was then checked and it was found that the field winding was shorted. As the field in this particular dynamic acts merely as a choke across the 96-220 volt output of the powerpack it would, of course have produced the above effect." W. P. Erickson, Omaha, Neb. Visual checking of resonance in ganged circuits: A visual means of indicating re sonance in radio-frequency sets can be arranged simply by placing a low-reading milliammeter in the detector output. The deflection on the meter will be changed by the strength of the carrier wave applied to the grid of the detector tube. With a given carrier wave, greatest deflection on the meter will denote resonance in the tuning of the set. In the grid condenser and leak method of detection the deflection on the meter will read downward. In the plate method of detection the deflections will read upward. The meter range should be 0-2 mA. M. Chernow, Polyphase Radio Laboratories, New York City Insulating lacquer in an A.-K. set: This was encountered in an Atwater Kent model 30 six-tube single-control receiver. This receiver while playing perfectly would suddenly drop in volume. The A battery and connections, power unit, set, and antenna were found o.k. With the set operating, it was found that by pressing on the condenser associated with the detector tuning coil the above condition would obtain. On the condensers in this set there are two screws which go through the bakelite end piece and screw into the stationary plates. From one of these screws the grid 7T 7" 1 0 2 3 4 5 6 GOO ■©■-0 « A SS The arrangement of parts on the rear of the tester panel is shown clearly in this picture. Panel layout of tester showing exact layout of parts. condenser is connected, and from the other the grid end of the tuning coil is connected. All brass screws in these sets are lacquered and it was found that the screw connection to the grid end of the coil was causing a high-resistance connection due to the lacquer. The lacquer was removed with a file and the set performed as it should. H. Weimer, Finkle Electric Shop, Appleton, Wis. Accuracy of Small Meters THE ACCURACY of small meters has often been the subject of service controversy. L. C. Nichols, manager of the New York Weston Front view of test set showing test plug and cable. office, writes us in reference to the more popular Weston voltmeters and milliammeters. " Models 528, 476, and 517 are all provided with etched-metal scales and on such instruments, whether d.c. or a.c, it is our custom to state the guarantee as 2 per cent, of full scale to allow for slight discrepancies between instruments which develop in the process of manufacture and assembly. The scale being fixed for any particular range we, of course, cannot calibrate for these slight discrepancies. "When considering direct-current measurements the Model 433 is correct well within 1| per cent, of full scale. The other instruments may have errors as high as 4 to 5 per cent., the amount varying to some degree with the scale. Briefly, the lowrange instruments are more sensitive to residual magnetism than the higher ranges in any of the models referred to. "The values given are considerably beyond any errors we have been able to detect, but it is our policy to state these inaccuracies rather high to avoid possible extended correspondence or dissatisfaction on the part of any customer. Business Kinks Frank J. Shannon, of Shannon and Wynkoop, radio service and Radiola specialists, of Philadelphia, Pa., gets right down to earth on several vital points of servicing. "We charge a time rate of two dollars per labor hour on radio service calls. As Philadelphia is so spread out that traveling time and expense mounts up somewhat, we charge traveling time on remote calls — some of our Philadelphia calls are twenty miles by auto from our shop and yet still within city lines. In cases where customer does not care to have us proceed after diagnosis and recommendations we have a minimum charge of two dollars. As to accessories, we charge the current list price — if they want cheap products and prices they can go to 'Radio Row' and take their chances. We, as a rule, always repair a set completely in the customer's home — whoever takes the original phone call requests the name of the radio, trouble as diagnosed by customer, and name and type of accessories. Then the man who makes the call carries accessories to cover probabilities of that particular set or sets. • JUNE 1929 • • 111