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Show ' i S S 2 ' Trouble-Shooting the B-Eliminator Where to Look and What to fj)0 When Power Supply Gives Out. By CHARLES GOLENPAUL, American Mechanical Laboratories. Trouble-shooting the B-eliminator tf.ould be a systematic process of elimination but with nothing eliminated elimi-nated until it has been checked up. In otl,er words, take nothing for granted, because things taken for granted are often the very things causing the trouble. We all recall the chap who took the automobile half apart, look-in" look-in" for the trouhle, when some one reminded re-minded hihi that his gas tank was emoty. Radio trouble-shooting can be very much the same. The first step in trouble-shooting the B-eliminator is to make sure that the 110-volt current is turned on, and that It is reaching the transformer primary of the device. The next step is to be sure that the fault lies with the B-eliminator, and not with the associated as-sociated radio receiver. With the trouble narrowed down to the B-eliminator, the logical procedure Is to start with the resistance bank and then work backward through the filter, rectifier tube, and finally the transformer. Lamp or Meter Test. A common trouble, when trouble does occur, is the absence of voltage at a given tap. This is generally traceable to an open-circuited or burnt-out resistor. Thus if the 10,000-ohra 10,000-ohra fixed resistor of the usual B-eliminator becomes open, the detector voltage volt-age will immediately increase, so that' in the tuned radio-frequency receiver the signal strength will be greatly diminished, di-minished, while in the regenerative receiver there will be constant oscillation. oscil-lation. 1 A defective resistor may be located I by means of a high-resistance voltmeter volt-meter connected to each tap in turn. The reading obtained at each tap should be approximately that called for by the designation on the tap. In the absence of a high-resistance voltmeter, volt-meter, a 15 watt, 220-volt incandescent lamp may be employed. It should glow a dull red on the full output and on the Intermediate tap of the B-pow-er unit. If it lights equally bright at, the detector tap it is an indication of 1 1 an open or defective 10,000-ohm fixed Jj" resistor. A satisfactory temporary repair can generally be made by means of a elarosliit connected between the plus binding post and the terminal which gives no voltage. The resistance is adju-tPil until the proper voltage is obtained, and this :-aves the trouble of seeking the correct value for a fixed resistor, while at the same time providing ample current-handling capacity, ca-pacity, Look to By.Pass Condenser. If the voitnge taps are found satisfactory, satis-factory, yet tlie receiver still fails to operate properly, the trouble may be due to nn open or an omitted by-pass condenser. A short-circuited by-pass condenner will act the same as a short-circuited resistor. If there is no voltage at all the terminals, ter-minals, the trouble may be traced to nn open circuit In the wiring, or in Hie transformer or choke coil wind-lugs, wind-lugs, or again to a broken-down condenser. con-denser. The wiring should be checked over for broken wires or bad connections. connec-tions. The transformer secondary and 'lioke coil windings can be tested, by menus 0f a telephone receiver and a !' coll, for continuity. Filter condensers con-densers can be tested by the same means, with a loud click at the time of milking contact and a weaker click Pn successive tapping of the terminals, ter-minals, to indicate a good condenser. If the successive clicks are equally loud, the condenser is short-circuited. Tlie rectifier tube should be considered consid-ered after that. The best method Is try n new tube or a tube known to sood, In place of the existing tube. T1s is especially true with the gase-01,s gase-01,s type of tube, which gives no other munition of its operation but a slight warmth. |