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I just replaced output transistors and a bad zener in power supply for this amp. Now there IS test loop current flowing (160ma) but the P1 bias pot is not doing anything when I turn it. I've tested that the pot indeed works and is connected to the other components too. What might be causing this?
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well I just found through continuity tests that Z3 and C10 were not grounded. They are in the right place on the board but for whatever reason (I did not bother to find out) they aren't grounded. So I jumpered a wire from there to where they should be grounded and the amp is fine... AND P1 now functions as it should, so I was able to bias it at the 200ma idle current. -
So one of your 15v rails was not working right.
You might inspect the board carefully, that missing ground could be a burnt off trace - it would happen at the most narrow spot. There could be related other damage that is not showing up at the moment but should be re;paired.Education is what you're left with after you have forgotten what you have learned.Comment
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I suspect you're right Enzo. I own the amp so I'm not too worried if it craps out again... I'll fix it then. thanks!Comment
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