Re: Help testing transistors

On Sep 26, 9:35 am, "Mavrik8511" <Mavrik8...@xxxxxxx> wrote:
I need some help with testing transistors. If I follow the advice of the online repair guides, they say to just put my DMM on Diode and ground the black lead and touch the red lead to the top of all of the transistors to check them. This really doesn't seem like it is "testing" the transistors.
I have seen other sites that say to touch the black lead to the top of the transistor and the red lead to each of the legs and check the reading. It is supposed to be between 400 and 600. But I get readings that are all over the place, from 615 to 710.
Can someone give me a little help in the best way to check transistors.

Thanks All,
Maverick
mavrik8...@xxxxxxxxxxx

For testing purposes, transistors may be treated like two diodes.
There will be a PN junction between the Base and emitter and another
PN Junction between Base and Collector.

For each junction you should see a large change in resistance when you
reverse the leads for measurement. Do not worry about the resistance
numbers. Transistors are physically constructed in a thousand
different ways and will display various readings.

The trick is to know what's wrong, not necessarily what's right.
First off, accurate transistor tests need to be performed out of
circuit. Otherwise you can read through other components. Things that
are bad:
[1] the same reading both wayss on a PN junction
[2] Low (0 Ohms) reading from collector to emitter.
[3] any infinite treading in both directions.

AL

.

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