Radio Broadcast (May 1928-Apr 1929)

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The Service Man's Corner THE number of radio service men appears to be increasing with great rapidity. Many service men, both old and new are readers of Radio Broadcast and quite naturally look to these pages for information of specific help to them in their daily problems. It is true, in a sense, that every radio article is of some help to those working in the field, but articles prepared with the problems of the service man chiefly in mind are badly needed. Regular features now found in this magazine are designed to be of general help to those working in this field. In this classification fall the Radio Broadcast Laboratory Data Sheets, Radio Broadcast's Service Data Sheets on Manufactured Receivers, "Strays" from the Laboratory, "Our Readers Suggest . . .," and to a certain extent, Radio Broadcast's Home Study Sheets. And, beginning with the November issue, we started a series of general articles on radio service problems by B. B. Alcorn. The chief problems encountered in the field by service men are classified in order of their importance by Mr. Alcorn as follows: 1. Dead tubes. 2. Run-down batteries. 3. Open circuits. 4. Defective parts. 5. Defective grounds. 6. Use of various "gadgets." 7. Defective antenna. 8. Misconnections. 9. Short circuits. 10. Lightning arresters. A few of these problems were discussed in Mr. Alcorn's November article. In later articles, he treats of the others. Do men actually facing the problems of curing sick radio sets in the field agree with this estimate? If not, in what order do they list the troubles? What interesting shortcuts to the work in hand have they evolved? What simple test-sets have they built for their own use? What small and persistently annoying little problems have been solved in practise? Wouldn't a short description of any one of these pet ideas prove helpful to others doing the same sort of work? "The Service Man's Corner" will be a regular feature of Radio Broadcast from this issue on, and contributions from service men and professional set builders are welcomed and will be paid for at regular rates. WHAT ONE SERVICE MAN SAYS THE data that I feel is most needed by the service man is along the lines of test apparatus that he can construct himself, and so know the whys and wherefores of what is happening when he uses the test sets, I have found a number of service men who can use the more elaborate test sets put out by several concerns. But few of them understand what the different readings show them about the condition of the receiver under test. These really fine pieces of apparatus are not serving their purpose unless they are in the hands of one who really knows how to use them." This service man concludes: "The servicing of radio receivers is a profession that no one need be ashamed of and the radio industry would certainly suffer if all service men were to be removed from the field." The radio service man will not depart from the field, for he is too valuable a part of the present radio structure. "The Service Man's Corner" in Radio Broadcast will, we hope, be of help in making his work easier, by affording a medium where ideas and comment useful to him can be exchanged. Field Suggestions \ A / HEN I received a letter from the editor of ^ * Radio Broadcast, suggesting that suggestions from service men would be appreciated and asking if I had anything to say, 1 felt much as I would if anybody had hinted that 1 might improve Bobby Jones' drive. And — in case you V\ TITH this issue, we start a regular page W for the practising service man. This department will, we hope, he a forum where service men can discuss their problems, get their pet ideas into print, and see now and then a hint which will he useful in their daily work. Contributions, which preferably should be short, to the point and typewritten, are solicited and will be paid for if used. Address your articles to the editor, "The Service Man' s Corner.' -The Editor. don't know — my golf drive looks like a sine wave. 1 have fooled around with radio receivers for some time, starting just after "ham" radio opened up after the war, so 1 can safely say I know nothing about radio. (You know, when you first start, you know it all). I've picked up a few kinks, most of which are doubtless ancient history to real service men. But I am glad to write about them in the hope that it will help bring to light some really good information on the subject from others. There seems to be a surprising dearth of information on the subject; I can't find any book that covers it. Use of a Set-Analyser: The service man should have in his kit a good set analyzer, of any good make. Working without one makes the job harder than necessary, and the use of one has a valuable psychological effect on the set owner, which is worth something. This unit should be capable of measurements on both battery and a.c.-operated sets, and its use should be thoroughly studied. Another tool almost as useful is a modulated oscillator that will cover the broadcast spectrum, which can be modulated for balancing sets using neutralized circuits. I have one that is small, selfcontained, and does the job. Single-control sets are now in wide use, and if the condensers in the set under test do not gang or do not follow very closely, the receiver cannot give its best performance. One of these oscillators will permit the service man to adjust the condensers to a nicety. Unless there is an adjustment provided, you do it by bending condenser plates, of course. The plates will get out of line in shipping, even when every care is taken at the factory. That, we are sorry to say, is not always the case. (A modulated oscillator was described on page 90, June, 1927, Radio Broadcast). A tool 1 want is a tube checker working off the a.c. light socket to handle any of the usual tubes. They are on the market, but the price is too high for me and I am hoping Radio Broadcast will tell us how to build one. [A description of such a tube-checker as constructed in our Laboratory will appear in "The Service Man's Corner" in an early issue. — Editor.] ■ • — H. J. Goddard, Ellendale, N. D. M miscellaneous service suggestions R. GODDARD has noted down some other service suggestions, which follow: Line-voltage control: The advent of a.c. sets has shown up the floppy condition of the average commercial power line as nothing' else could. Many a set is hooked to a line that varies from 105 to 125 volts. The latter condition is especially hard on tubes. Every service man should see to it, if the line voltage is high, that it is reduced to normal before it reaches the set. A 50. ohm resistor that will handle around 40 watts will do the trick. I like them variable particularly if they can be mounted on a bracket in a console, out of sight. They are cheap and will pay for themselves in no time. 1 'd like to see some reputable company build such a resistor that can be plugged-in between the outlet and the set plug so that a turn of the cap will permit adjustment. There should be a big sale for them. [A number of resistors which can be used for this purpose are now on the market. Although none of them have precisely the features which the writer desires, the adjustable units are satisfactory for the purpose.— Editor.] Excessive plate voltage: Don't forget that a high plate voltage is almost as hard on a tube as high filament voltage. Watch that plate voltage if you want your tubes to last. Blinking a.c. tubes: Every now and then you find an a.c. tube that is a blinker. These tubes start all right when cold, but when heated, a small break in the heater filament separates and for all practical purposes, the tube goes dead. When it cools a bit the ends come together and the tube starts again. I found a bad case of "fading" due to this very thing. Watching the tubes and noting which filament goes black of course localizes the trouble. [See p. 428 Radio Broadcast, April 1928, where this point was discussed at some length. — Editor.] Ca ut ion : Ever notice the instructions to keep your hands out of a set when the a.c. is on? Manufacturers do that because they are sore at the mortician. 101