Adcom amp has no bass

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If they lost their heatsink, that is very likely the reason they burned out.

Be aware that you need special chemicals to thermally attach the heatsink to the transistors.
 
In the scheme they're Q1 and Q2, Should they be replaced or would it be likely they're still good and burned out C3?

Also, could I just use JB weld or get some thermal double sided tape?
 
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Best to just replace them all; easy and cheap enough.

Tape is not great, but will-do. The better solution is thermal paste. That is assuming the heatsink itself is attached physically in some other way.
 
Well, that explains how it came off..

I suppose the thermal double-sided tape is the way to go then. Or you will have to make a mod in a property attached heatsink.

If you are using tape, be sure to clean both services with alcohol first.
 
Think I'm going to get thermal conducting epoxy for these, they're VERY small and I'm not sure I'd trust tape with that little surface area.

Am I able to up C9 (47uF 25V) to a 50V without much problem? I have them sitting here, and the 47uF 25V that I got were much bigger than than the one on the board. I could use them but I'd have to leave the leads quite long
 
Like the epoxy idea, if it's heat conductive enough.

A (somewhat) higher voltage capacitor is alway a plus!
 
Well I messed it up. I don't know, maybe my soldering wasn't good. I just did the right channel and now it sounds all scratchy and distorted, though maybe the bass came back if it didn't sound so bad. I changed out C3, C7 and C9 on the input stage.
 
I just tried to re-solder C3, now when I turn on the amp the speaker gets a straight negative DC charge and the woofer sucks in and stays there...this thing is toast. I may try to fix the left channel and use it as a subwoofer amp or something.

edit, I even tried point to point to bypass the board, because C3 is wired in parallel with C4, I matched where they should go and no luck, still straight DC to the speaker. I don't want to damage the VC by continuing to try. Very sad!
 
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Since this is a completely blown unit, are there parts I should salvage from either the board or the unit itself? Capacitors or MOSFET's? That big azz transformer?
 
I can't really tell what's going on there, so I can't judge weather it's hopeless or not. But if you're done with it and don't have use for any particular part of it right now, it is probably best to just sell "as is".
 
I can't continue. I tried just replacing the C3 cap on the left side, and it worked and the bass came back and everything for about 10 seconds, then POOF, smoke and straight DC to the speaker. So the boards are toast. I might throw it out there as a parts device for someone who works on them but I doubt I'd get anyone interested.
 
CJ Payne said:
In the scheme they're Q1 and Q2, Should they be replaced or would it be likely they're still good and burned out C3?

Also, could I just use JB weld or get some thermal double sided tape?
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Hi CJ,

Did you ever have luck getting your Adcom GFA-5500 "no bass" issue fixed? IO have the same problem.
 
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