Radio Broadcast (May 1928-Apr 1929)

RADIO BROADCAST An outfit of this sort proved itself worth while to the department editor in the case of a batteryless installation in a d.e. district of New York City. \oi>> reception in this i articular apartment removed radio from the entertainment class. However, by using a portable receiver, operating entirely from independent battery sources, it was easily ascertained thai the pickup was conductive through the lines. The receiver was rewired for battery reception (a desperate remedy) and has been giving satisfactory service ever since. An Unusual Problem: The following incident came to my attention while servicing an Atwater-kent battery receiver equipped with an V -power unit, and perhaps a little information about it might help a brother service man. The set was playing along nicely when I arrived, but a moment later the thing stopped dead. After about 30 seconds the set gradually began to play and soon was up to its full \ olume. As nothing like this had happened before installing the power unit, of course, this wras blamed. A careful check of both the A and B-power unit circuits failed to reveal anything. A wire from the power rheostat in the A-power circuit seemed to be a little loose, but installing a new power rheostat didn't remedy the trouble. By carefully questioning the owner of the set 1 discovered that some time before a verysimilar trouble had developed in the set when it was operating from batteries. The music had died down but hadn't stopped entirely and by working the filament switch the full volume of the set could be brought back. This led to the inspection of the filament switch. Sure enough there was the trouble. This is how I doped it out The filament switch with a slight jar or other disturbance would cause a poor connection in the filament circuit. This, in turn, would cause the voltage in the A-power unit to rise due to the reduced load. The condenser in this particular unit (a Hartford with an electrolytic condenser and Tungar full-wave rectifierl would blow as soon as 8 volts or more was pushed into it. It took the condenser perhaps three seconds to heal and the remainder of the thirty seconds to charge up again. After repairing the switch this trouble disappeared entirely. Alton R. Bow ex. Pleasant ville. N. J. All In a Day's Work: Here are two difficult problems which I solved more or less by chance. The trouble was similar in each case and may aid in solving related troubles found by brother servicemen. The first, a Freed Eisemann model 57. had been working very satisfactorily. One day on turning it on it was found to have lost its volume even on local stations. On checking it with an analyzer, the amplifier and power potentials were found to be considerably less than normal. In checking the power pack I found it o. k. I turned the set upside down and turned it on and noticed a minute curl of smoke as I pulled the wire running from the plate of the power tube to the jack. On closer inspection. I foimd the insulation of this wire was leaking and. as it was cabled with a ground wire, it practically caused a short circuit. When these wires were separated and the plate wire replaced (as it was burned badly') the set acted normally again. The other was a Fada battery model which had lost its pick-up and even locals timed broadly with no great kick. This set checked perfect. When I had it out. however. I noticed that where two wires went through the metal parts of the frame circles of corrosion had formed. By replacing these wires with new insulation where possible and by entire new wires in places where this was impossible, and rebalancing the set. normal reception was obtained. In both these cases the wire involved was covered with a material similar to black cotton and impregnated with wax. It is not so good! George YV. Brown. South Boston. Mass. The D. C. Problem: Supplementing your editor's remarks about the portable receiver and artificial "static" in d.c. districts. Arthur R, Gerling, of Kellogg and Bertine, New York, writes: During my eight years of selling and servicing radio receivers in the wealthiest d.c. district in the United States, I have acquired a knowledge of what the elite want in the way of radio entertainment and reception, and also ^adio Sej'vice For Particular People % Now is a good time to have the Radio looked over, tested, and put into first-class condition. A radio receiver is a very delicate piece of apparatus and no matter how well constructed should have attention from time to time to maintain it in order for best results. Often a little work of this kind will make a marked improvement in quality of reception. Batteries, Eliminators, Tubes, Aerial should all be in proper order. We are technically trained for this work, have the most modern tools, testing outfits, and appliances for performing this work in a workmanlike manner, at reasonable prices. A postcard or telephone call will receive prompt attention. Endorsed by National Radio Institute, Washington, D. C. William V. Lowe Bos No. 387 Tel. 352 7-M Fitchbur'g, Mass. Fig. 2 — .4 neat specimen of radio service-sales literature that brings returns for William V. Lone, of Fitchburg, Mass. the bug-a-boos that sometimes prevent us from giving them just what they want. These folks whom I have chosen to call the elite would be quite satisfied — for the most part — with just the same kind of reception that their chauffeurs get out in the Bronx (where a.c. current is supplied). In many cases even this is denied them — why? First, because they are burdened with d.c. current with its many disadvantages known to all sen icemen. Second, the management of the apartment houses in which they dwell often have stringent rules regarding the erection of antennas, and usually forbid them entirely — quite a reasonable attitude. Tliird. the numerous d.c. motors always found in large apartments— elevators, refrigerators, exhaust fans, water pumps with their armatures spitting fire and interference with every revolution. These are a few of the things that the ser\i ceman has to think about when installing the present-day d.c. set, plus the natural loathing of the "madame" to have wires stretched here and yon about her drawing room, boudoir — or what have you. The several sets now being put out by leading manufacturers are successful in only a comparatively small percentage of cases, and these very often because of the industry of the serviceman making the installation as regards filtering motors — known to interfere — putting filter banks in the d.c. fine — experimenting with antennas, etc. Is the manufacturer really interested in helping to solve this d.c. problem by putting out a set that will cut down d.c. interference to a minimum, or must the serviceman continue to rub along as best he can under the circumstances? My answer to the d.c. question is: A superheterodyne using a loop — disappearing when not in use — 201.\-type tubes — d.c. operated — console cabinet with a self-contained dvnaniic loud speaker. Price range $350.00 to $500.00. \\ hat is your answer? Solve it and the residents along Park Avenue will forever be in your debt. [By the way, the portable used by the editor was exactly this]. Neal Connections with Bell Wire: It is possible to use ordinary bell or annunciator wire for hook-up and for external wiring purposes without having the work marred, as far as appearance is concerned, by frayed ends. If first the outer cover is unwound as far back as desired, then the inner covering, which is wound in the opposite direction, is unwound to the same point, and the two loose ends tied together and clipped short, there will never be any ragged ends hanging loose. J. H. Bond, Dallas, Texas. Testing Audio-Frequency Transformers: When going on service jobs I always carry a carbon microphone button with me, which can be shunted across the primary of the first audio transformer in series with a six-volt battery. If. on speaking into' it. the voice comes through well, the audio channel can be eliminated as the source of trouble. Bernard J. Cannon, Pittsburgh. Pa. [Another simple way of accomplishing the same test is to connect a loud speaker across the grid leak of the detector tube, and speak against the diaphragm. The unit from an old horn-type loud speaker may be included conveniently in the service kit for this purpose. It is, as Mr. Cannon suggests, the simplest test for the audio channel — Editor}. Defective Transformers: The usual tests for an open primary will not locate a microphonic transformer winding, which is the cause of a great deal of trouble down here in Florida. I have run across several cases of transformer trouble that tested o.k. with a battery and milliammeter, but were defective in operation, due, probably, to the dampness of climate. When suspecting trouble of this nature. I connect a 4.5-volt C battery across the primary of the transformer and a pair of telephone receivers across the secondary. A defective primary will generally show up. as a loud scratching, after a few seconds. The effect, of course, is stepped up by the transformer. C. Washburn, Jr. Jacksonville, Fla. Noise in the volume control: Here is a suggestion for remedying a difficulty which has turned up in some instances. If a set had not been used for some time and the weather has been damp, slight oxidation may occur at the point of the volume-control contacts. A condition of this kind, will cause some noise when the volume control is adjusted. Fada Sales points out that, although such a condition may not always be apparent, it is easily fixed by moving the contact arm back and forth until the slight oxide coating has worn away. Watch for bad contacts: Two simple sources of improper contact which may cause trouble are worth mentioning. Receivers equipped with loop antennas connecting to the receiver through a plug and jack arrangement may develop noise due to dirty contacts. This trouble is quickly stopped by rubbing the plug with a bit of fine sandpaper. Contact prongs in the house-lighting plug circuit connecting the receiver to a convenience outlet may become slightly bent so that the contact in the outlet is not tight. Noise resulting from • march, 1929 page 320 •