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Re: [Amps] Alpha 87A - strange power related issue

Subject: Re: [Amps] Alpha 87A - strange power related issue
From: Eric Dobrowansky <>
Date: Tue, 11 Oct 2022 23:34:07 -0400 (EDT)
List-post: <>
I did some further troubleshooting last evening. After ruling out the power 
switches and the adhesive under the 1000uf cap on the ac input board,  I 
determined the return path of the relay was not being opened. I then moved on 
to the control board.

Sure enough, after some measurements, I determined the negative return path at 
the control board connector was not switching properly upon power down. I 
suspected the transistor or optoisolator on the AC relay's return (-) side, but 
while doing some troubleshooting measurements, I must have disturbed something, 
and the issue resolved itself. No apparent cold solder joints were found. I 
suspect either there was some leakage via dust buildup, or possibly one of the 
ferrite beads on the leads of the transistor was conducting. I did move the 
transistor slightly while testing it.   

So far, as of today, after repeated cycles of connecting the AC power cord, and 
power cycling the amp, everything is working normally. Worse case, if it occurs 
again, I will look to replace the opto and transistor.

Thanks again for all the suggestions.

PS - If the Alpha 87A IO list moderator is monitoring this thread, maybe you 
can approve my membership request. It's been pending approval for a few days 

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