Radio Broadcast (May 1928-Apr 1929)

Practical Talks to Service Workers THE ROUTINE TESTING OF RECEIVERS THE value of an efficient, logical routine in testing radio receivers of all makes, models, and social standing can hardly be over-emphasized. The Oxford Dictionary defines the word routine as: "Regular course of procedure, unvarying performance of certain acts, performed by rule." No matter what sort of work one does, any part of which is purely mechanical repetition of the same acts day after day, even though intelligence is required to watch, tabulate, and draw conclusions from the results obtained, much time may be saved and energy conserved by developing an unvarying system of performance of those acts. Fundamentally, there is little difference between radio receivers, and it is entirely practical to devise a routine which may be used universally for the efficient testing of virtually all of them. Use of Diagnoser IF THE routine of testing used is to be equally applicable to all sets, then testing equipment must be used which may be applied to all sets with equal facility. The socket contacts of the average modern receiver cannot be reached when the tube is in the socket, and that remains true in some sets even after the chassis has been removed from the cabinet. As it is highly desirable to make some of the essential tests under load conditions, it becomes necessary to use a set-diagnoser ("analyzer" or "tester") to attain that end. If for no other reason, that application alone would be ample justification for the use of such a device. Fortunately, the set-diagnoser has many other advantages which make its use by all servicemen imperative if they are to approach closely the maximum efficiency in doing service work. The set-diagnoser has three distinct and important advantages. It permits a number of essential tests which either are impossible or would consume a totally unjustified amount of time with lesser equipment. It makes all the tests that can be made with ordinary single meters, in much less time. And it has an exceedingly beneficial effect on the customer's impression of the efficiency and ability of the serviceman. Cost of Equipment THERE are a good many servicemen and service organizations who are of the opinion that the cost of the manufactured setdiagnoser is prohibitive. We believe a small amount of simple arithmetic can effectively dispel that myth. Five minutes is a conservative estimate of the time saved on the aver There is nothing mysterious about any radio. Every trouble in radio can be found without the aid of spiritualism, psycho-anal-ism, or guess-ism By JOHN S. DUNHAM Q R V Radio Service, Inc. age service call by the use of a good setdiagnoser (we are assuming that the serviceman knows his business, makes all the tests he ought to make, and is thoroughly familiar with his equipment). It is also conservative to assume that the average serviceman can make an average of six service calls per day. Multiplication of six calls by five minutes per call gives a product of thirty minutes saving per day. The serviceman ought to bring in at least two dollars per hour for his organization, or for himself if he is working alone. At that rate, the saving of a half hour per day would represent a saving of one dollar per day. The cost to a service concern of a good set A question many dealers and servicemen frequently ask is, " What is the best order of procedure in servicing receivers?" Each service problem is at once the same as every other and different from others. Mr. Dunham, head of one of the largest New York City service organizations, here discusses some of the outstanding phases of this question, and, while he does not attempt hard and fast rules, his thoughts should interest and help those doing this work. — The Editor. diagnoser is not over $75.00. Paid for at the rate of one dollar per day, three 25-working day-months would accomplish that object. For the remainder of the life of the instrument, the daily saving would be clear profit. The foregoing computation considers only the saving in time, while the money value of the other advantages, added together, is certainly equal to that of the time saved. In the opinion of the author, two months is a fair estimate of the maximum length of time required for a set-diagnoser — properly used by an intelligent, well-trained serviceman — to pay for itself. Even some of the radio set manufacturers have begun to realize the value of their use, and when manufacturers generally come to the conclusion that any particular thing would be advantageous in performing service on their sets in the field, then you may be certain that progressive service organizations came to the same conclusion about two years previously. The American Bosch Magneto Corporation says, in part, in their dealer service manual: "With the introduction and almost universal approval of the a.c.-type radio receiver by the public, the use of some standard and approved radio test set is absolutely essential." Logical Routine Tests THE ability of a radio serviceman to thoroughly and quickly discover the troubles in any receiver is largely a function of his ability to think logically and to approach the problem, serenely, as one which may always be solved by a process of orderly elimination and orderly reasoning out of cause from effect. Every action, whether mechanical, elec • april, 1929 . . . page 375 # trical, or chemical, which takes place in a receiver or its associated equipment, is governed by known laws, and any variation from normal action can be determined by known methods. There is nothing mysterious about any radio or any radio trouble, except to the man who is not familiar with them. Every trouble in every radio can be found without the aid of spiritualism, psycho-anal-ism, or guess-ism. Present-day radio receivers are composed primarily of tubes, and secondarily of circuits employed to couple and supply those tubes. As the tubes are the heart of the machine, and the coupling and supply circuits both arteries, veins, and nerves, so are the tube sockets the nerve centers, at which most of the needed information about what is "oing on in the rest of the system may be obtained. Therefore, any logical system of testing must start at the sockets. More information may be obtained there, far more quickly, than at all other points. One end of each plate, grid, and filament circuit terminates at a socket, and the other end of each of those circuits terminates at the same socket. At the sockets one may get plate, grid, and filament voltages, and plate and filament currents. Tube Tests TUBES are at once the most important and fragile of the things that comprise a radio receiver. They are the most prolific source of trouble, and, as progress is made by manufacturers in the elimination of other troubles, the ratio of tube to other troubles increases. The serviceman's first object in testing a receiver should be to get as quickly as possible to the business of testing the tubes. They cannot be tested properly, however, unless the voltages applied to them are approximately correct. One must, therefore, test filament, plate, and grid voltages at each socket before the tube may be tested, a statement which requires a degree of modification depending upon the type of set. Obviously, one does not get grid voltage reading at a detector employing a grid condenser and leak, for no grid voltage is applied when that method of detection is used. Even if it were, the drop caused by the very high resistance of the leak would be sufficiently great to overcome the small applied voltage. Neither is it feasible to test tubes from other sockets to which no grid voltage is applied. In old battery-operated sets which remain guiltless of a C battery — of which, fortunately, there are few left — the only recourse in testing the tubes is to abandon the set entirely, connect the batteries, and one of the 4.5-volt C Any logical system of testing must start at the tube sockets