Posted by Wayne Parham [ 68.91.14.67 ] on January 07, 2005 at 02:49:05:
In Reply to: Re: OOOPS it just went bang! posted by matt on January 07, 2005 at 02:39:29:
You are looking for continuity on PN junctions when forward biased and open circuit when reversed biased. Every junction should show this reading.
So here's how you check it.
Connect your meter with (+) to a "P" junction and (-) to an "N" junction, and it should show continuity. This is forward biasing the junction. The reading will usually be from 5-50 ohms, depending on the transistor and the battery in the meter. Reverse the leads, (+) to "N" junction and (-) to "P" junction and the meter should read open. This is a reverse-biased connection.
Then connect from collector to emitter and test forward-bias continuity. If an NPN transustor, the collector is positive and the emitter negative to forward-bias and you should have continuity. PNP transistors are forward-biased with the collector negative and the emitter positive. Reverse bias the collector to emitter and it should show open.
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