Re: Amplifone, testing SCR (Q4)

If using a DMM put the positive lead on the anode of the SCR, the
negative lead on the cathode. It should measure open. Momentarily
touch the gate lead to the anode lead and it should turn on, even after
the gate lead is disconnected. Momentarily remove and reapply either
DMM lead and it should be off again.

That being said, there are a LOT of assumptions in the above proceedure.
 One is that the DMM puts out enough voltage to see the SCR turn on,
enough current to keep it on once triggered, and that the leads of the
DMM are the polarity you think they are. DMM leads are usually the
correct polarity, old meter type VOM leads are usually backwards.

Tony Jones wrote:

>How do you test the SCR (Q4) on an Amplifone HV board?
>
>The FAQ says "just pull it and test on diode test. If you are reading an open
>circuit or short in any direction, you'll have to replace it.".
>
>By "any direction" does it mean any of the 6 possible test lead combinations?
>
>Tony
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Received on Tue Apr 1 11:33:55 2003