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THE SERVICEMAN'S EQUIPMENT By J. H. MILLER Chief Engineer,. Jewell Electrical Instrument Co. Importance of Service Equipment; Details of Two Types of Jewell Radio Set Testers, Models 409 and 199. Model 409 Set Tester. The fundamental purpose of any device for testing receivers is to make possible a quick and accurate measurement of the voltages and currents supplied to the va- rious tubes in the receiver. Practically all the important circuits in a receiver finally end at the terminals of the various tube sockets; accordingly if measurements are made at the tube socket terminals of all but attention should also be paid to the speed with which tests may be conducted. A set analyzer with four instruments, such as the Jewell model 409, is more rapid in operation than the Jewell Model 199 which utilizes only two instruments. The two additional meters on the Model 409 are available for continuous reading of plate voltage and plate current, an obvious advantage since these two quantities can be noted at any time during the test. By using all four meters simultaneous readings can be taken of filament or heater voltage, grid voltage, plate voltage, and plate cur- rent. The adapter plugs supplied with the instrument have five prongs so that meas- urements may be made on tubes which have their cathodes biased with respect to the filament. Four-prong adapters are also supplied so that measurements may be made on all types of four-prong tubes. In these Jewefl set analyzers all of the instrument terminals are also brought out to separate binding posts so that the in- struments may be used separately to make other measurements. For example, if the maximum voltage from the B supply is to be determined two leads can be run from the B-power unit to the two binding posts that connect to the high-range voltmeter, and, by pressing the appropriate push button, the maximum B voltage may be measured. Having the various instru- ments available at separate binding posts also makes it possible to make measure- ments to determine the value of resistors, the voltages and currents it is not difficult to de- termine in what circuits defects exist. If when checking any particular socket a defect is indi- cated, a good tube can be substituted and if the defect disappears the fault was obviously due to a bad tube, whereas if the defect remains some circuit in the receiver is evidently at fault. Good instruments for servicing radio receivers are made by a number of manufacturers who have spent considerable time and effort to make such equipment complete, ac- curate, and rapid in operation. In selecting service equipment the cost is, of course, a factor condensers, etc. Proper testing apparatus is ob- viously essential in the servicing of radio receiv- ers and any serviceman who knows something about the circuits of sets can double his efficiency with the proper kind of servicing equipment. If records are kept of all of the readings on an analysis chart of the type illustrated, the logic of the method cannot be questioned. If a carbon copy of the analysis is left with the set owner, it is just as much of a receipt as a prescription which the physician leaves, if only for sugar- coated pills. And, in the long run, the service (Continued on page 297) RADIO BROADCAST FOR MARCH 269