Radio Broadcast (May 1928-Apr 1929)

JULY, 1928 A UNIVERSAL SET AND TUBE TESTER 149 open, as it is not used. Push the upper part of the adapter into the tube base as far as possible and glue in place. Solder the ends of the wires to. the prongs, leaving rounded ends as before. Now solder a phone tip to each end of the 5-foot flexible rubber-covered wires. You should now have a tester completely wired with a cable and plug attached, two flexible rubber-covered leads with phone tips on each of the four ends, one UY-227-to-ux adapter with phone tips on the filament leads and one ux-toUY-227 adapter, in addition to the five other adapters named in the list of parts. The panel layout of apparatus is shown in Fig. 3 and the complete apparatus, tester and adapters in Fig. 1. FUNCTION OF THE VARIOUS PARTS THE d.c. voltmeter is for indicating the filament voltage in d.c. sets and the plate voltage and grid voltage in any set. The a.c. voltmeter is for indicating filament voltages in a.c. sets and power amplifiers. The switch, S3, is for connecting the proper filament meter into the circuit. The push button on the d.c. meter must be depressed to read plate voltage. The d.c. milliammeter is for indicating the plate current of the tube being tested, and in conjunction with switches, Si and S2, for testing tubes. With S2 on "Test" and Si on "C — ," a bias of 45 volts negative is put on the grid of the tube with respect to the negative leg of the filament. With Si on "C+," a bias of zero is put on the grid. With S2 on "Set," the grid of the tube is connected through the cable to the set. The switch, S4, is for reversing the d.c. filament voltmeter in the filament circuit to conform to different methods of wiring the filaments in receivers with respect to polarity. If this provision were not made, the meter would read backward in some sockets. The switch, S5, is for switching the d.c. filament meter from the filament circuit to the grid circuit for testing. Switches S4 and S5 are on the cabinet as shown in Fig. 1; Si, S2, S3 are on the panel. The cable and plug with its wooden handle is for plugging into the sockets of the receiver. The various adapters provided make possible the testing of any and all types of receivers, a.c. and d.c, old or new. The two flexible leads are for connecting to the a.c. and plate voltmeter meters for external tests by means of the tip jacks or binding posts provided. In my model no jacks have been provided for the d.c. filament meter because the a.c. meter gives an indication on d.c. although it does not indicate polarity. The socket is for inserting the tube to be tested. The UY-227-to-ux, WD-11-to-uv standard and the uv-199-to-ux standard adapters are for adapting any type of tube to the ux socket. The two filament leads from the uy227 adapter are plugged into the tip jacks connected to the a.c. meter when testing UY-227 tubes. The Benjamin socket will accommodate the short prongs of uv tubes and adapters. METHOD OF TESTING D.C. SETS AND TUBES LIAVE set to be tested connected * * up and turned on as for operating. Take out first tube in the set and insert plug of tester in its place, using one of the adapters provided if necessary. Throw switch, Sj, to "d.c," switch, S5, to "A," and switch, S2, to "SET." Read filament voltage from d.c. voltmeter, making adjustment of filament rheostat in set, if necessary to obtain proper voltage for type of FIG. 2 tubes in set; that is, 5 volts for 201-A tubes or 3 volts for 199's. If the meter tends to read backward, reverse the polarity by throwing switch, S4, until the meter reads correctly. If no reading is obtained, see that the A battery is charged and that the leads are making proper contact, both at battery and set. If no reading is now obtained there is an open circuit in the filament circuit. Try another socket and if the same result is had you are safe in assuming that either the battery switch, the rheostat or one of the main filament leads are open. Short-circuit each one in turn to locate open portion of circuit. When found the remedy is obvious. If no reading is obtained in only one socket, it may be that the socket springs are either dirty or are not in the proper position to make contact with prong of tube or adapter, or one of the filament leads to the socket is broken or disconnected, or there may be a high resistance joint in the circuit wiring. Check each item in turn until the fault is located, and then remedy. This must be done PUSH / VOLTMETER BUTTON M2 STUDS FIG. 3 before going forward with further tests. If the voltage indicated is excessive there is either a short circuit or wrong connection indicated. Check connections to batteries or power uniti. After making certain that the filament circuit and voltage is correct, depress d.c. voltmeter button and read the plate voltage. If the voltag; indicated is incorrect for the socket being tested, that is, 45 volts for the detector or 90 for a radiofrequency amplifier, adjust, after making certain the voltage source is connected and functioning correctly. (The two flexible leads can be plugged into the d.c. voltmeter jacks shown in Fig. 3 and used to test either batteries or power unit, keeping button depressed while using. Pull plug out of set while making this test). If no reading is obtained with the plug in the set and meter button depressed, it indicates an open circuit in the plate circuit. Short each portion of the circuit, such as the primary of a transformer or a radio-frequency coil and any stabilizing or volume control resistances which may be in the plate circuit. When the defect is located, remedy either by replacing or repairing defective part. The resistance of audio-transformer primaries, etc., must be taken into consideration when computing voltages. After making certain that the plate circuit and voltages are correct, throw switch, S5, to "C." The grid bias voltage, if any, should now be indicated on the d.c. voltmeter. If no reading is obtained, reverse switch, S4. If the detector socket is being tested, it will be necessary to short-circuit the grid leak and condenser with a small clip or piece of wire. Watch your meter closely as there may be a deflection of only a small fraction of a volt, depending on how much resistance and C-bias there is in the grid circuit. As this test is for continuity of circuit and not for accuracy of grid voltage, any deflection of the meter should be an indication that grid circuit is correct. Defects are located and remedied in the same manner as for the plate circuit. Check each socket in the set for these values in the same manner.