Radio Broadcast (May 1928-Apr 1929)

Fig. r. READY FOR A^Y TEST This compact tester combines the functions which once required the use of a varied array of meters and testing equipment. It is adapted for continuity tests on all the circuits of a. c. or d. c. sets, filament, plate and grid voltage test, and individual tests on tubes. A Universal Set and Tube Tester By D. A, R. MESSENGER I AM a radiotrician practicing general servicing, repairing and installation of all types of radio receivers. Given a couple of meters, some knowledge of the subject and some common sense, the testing of the older types of battery receivers and tubes was a fairly simple matter. But when all types of A, B and C voltage-supply devices and, later, when the new a.c. sets and tubes came on the market, the matter of testing and troubleshooting became something else again. In order to eliminate the necessity for a multiplicity of meters and other accessories, I devised an instrument that, used properly, would enable me to make all routine tests on all types of receivers, both a.c. and d.c. At the time, I could find nothing on the market which answered my requirements, so I designed and built such a tester, which is herewith described. The tester will assist in making the following routine tests: (a) . Continuity of plate circuit. (b) . Continuity of grid circuit. (c) . Continuity of filament circuit. (d) . Voltage applied to plates of tubes. (e) . Voltage applied to filaments of tubes. (f) . Voltage applied to grids of tubes in some sets. (g) . Each tube in receiver. (h) . Milliampere drain of each tube and of the whole set. The actual construction of the tester is simple enough if you consult the accompanying photographs and wiring diagram. The paragraphs which follow may be useful to other service men and to those who wish to duplicate this unit. PREPARING THE PANEL HpHE panel is drilled for the meters by scribing on the reverse side a circle which has a diameter the same as that of the meter, and drilling around this circle with a \" drill, making each THE writer oj 'this article, who is a service man in Washington, D. C, describes in straightforward style the assembly and use of a universal set tester. This useful instrument was designed especially for routine service work. With it all manner of tests on d.c. and a.c. radio receivers are possible. The various tubes in the set can be tested, and the voltage of batteries or B-power units can be determined. This universal tester should be the service man's most useful tool, but it should also appeal to home experimenters who want to add an inexpensive and useful test set to their home laboratory equipment. ■ — The Editor. drilling as close to the previous one as possible. When you have drilled the complete circle, break out the center and finish the rough edge with a small half-round file. The Benjamin socket is mounted by scribing a square if" on a side. Drill a j3F" hole in each corner, and a i" hole in the exact center. The switches are mounted in T7j" holes, and the tip jacks in f^" or f" holes. Lay out instruments on the panel in such a manner that the completed tester will present a neat and symmetrical appearance. The illustrations may be of some assistance in this respect. Care must be exercised in wiring so that no exposed wire can come in contact with any other wire or any of the jacks, switches or measuring instruments. The C battery can be fastened in the bottom of the cabinet with a couple of small brackets or strips of thin brass or aluminum. The cable is soldered into the circuit and the free end brought out through the same hole that was provided for the old cable from the Radiola 111. The cabinet from this receiver served nicely to house the apparatus for this tester. Those who do not find such a cabinet can house this unit in any 148 similar cabinet which, if desirable, can be home made. MAKING THE TESTING PLUG TTHE testing plug is made up as follows: *■ Drill a f " hole lengthwise through the center of the 1" X 3" piece of wood. Round one end off to make a convenient handle and taper the other end slightly to make a snug fit in a ux-199 tube base. Clean the old glue thoroughly from the inside of the tube base and melt the solder from the prongs. It may be necessary to drill out the center of the prongs with a drill. Pass the cable through the handle and strip the insulation for about an inch from the end of each of the four wires. Connection to the tube base is made by passing each wire in turn through the proper prong (from the inside — with reference to the bakelite collar) and soldering in place. Make nicely rounded ends with the solder or you will have difficulty getting the plug into a socket later. The wood handle is now pushed into the tube base as far as possible and glued in place. Now prepare the UY-227-to-ux adapter by soldering a phone tip to the end of each of the rubber-covered filament leads. Do not cut these leads short, for they should be long enough to reach from the tester box to any set which may be tested. Now prepare the UY-227 tube base as you did the ux-199 base. Take one of the ux-to-uv-199 adapters and break off the bakelite from the lower part. The section which makes contact with the socket prongs is a separate piece and has four brass studs riveted to it. Cut each of these studs off to about \" long. Solder a short piece of bare flexible wire to each stud. Slip a piece of spaghetti f " long over each of these four wires. Then pass each wire through the proper prong in the UY-227 tube base, that is, the wire from the plate opening of the adapter through the plate prong, etc. Leave the cathode prong