Emerson-Radio-and-Phonograph-Corp-120291A 电路原理图.pdf

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1、V.T.V.M OHMMETER CHECK OF TRANSISTORS An approximate check of the transistors may be. made with a vacuum tube typeof ohmmeter. They are checked as two separate crystal diodes might be checked, that is, by measuring the forward and inverse resistance of each section in dividually. Figires No. 2 and N

2、o. 3 shows the method of testing P-N-P and N-P-N types of transistors used in this receiver. When the negative terminal of the ohmeter (set on R x 10 scale) is connected to the base (B) terminal of a good PNP transistor and the positive terminal of the meter is connected to the collector (C) or emit

3、ter (E) terminals, yau should measure a low resistance (in the order of 500 ohms or less). When the positive terminal of the ahmmeter is connected to the base (B) terminal of a good PNP transistor and the negative terminal of the meter is connected to the collector (C) or emitter (E) terminals, you

4、should measure a high inverse resistance in the order of 50K ohms or higher. In the event your results are opposite from these, it is possible that the plus side of your meter is actually connected to the negative side of its internal battery. NPN type transistars are checked in a similar manner exc

5、ept the applied polarities from the ohmmeter are reversed (see figure no. 3) to give same inverse and forward resistance results. CAUTION Use only a vacuum tube type of ahmmeter. The R x 10 scale must be used for all forward (low) resistance measure ments. Do not use the R x 1 scale as this might damage the transistor. A shunt type ohmmeter should not be used. If in doubt as to the typeof vacuum tube ohmmeter you have, place a 1,000 ohm resistor in series with it and subtract this 1,000 ohms from the reading obtained. 34 收音机爱 好者资料库 RadioFans.CN