Transistors stuck to heatsink

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Recently picked up two amps in a trade.

Neither are working :)

(I was aware of them not working when I got them)

One is an Adcom GFA-5500, and the other is a Krell KSA-200.

The Adcom was something the that he threw in as he was doing spring cleaning, which was very kind of him!

I’m starting with the Adcom, and I’ve pulled it apart, but can not get the transistors to release from the heatsink?

In order to start working my way through the amp boards, I need to get them off the heatsink.

Any thoughts on how to get them to safely release?

Thank you in advance for any thoughts!



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Grease might have dried up or silpads might have crystallized, I´d drop a drop of WD40 oil on transistor edge and let it seep in a day or two to soften things up.
In any case you´ll need new mica - grease - silpad afterwards; you can wipe trasistor cases clean with some solvent, think acetone - toluene - lighter fluid.
Alcohols are not strong enough.
Patience is your friend.

Plan B: gently warm up transistor body with a heat gun but in this case NO solvents anywhere near.
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Thank you all!

Yeah, that’s the amp board/heat sink situation as you photographed. Except it’s blue.

I have some WD40 liquid wrench? Lighter fluid has been a go to for removing decals off stuff, happy to try that also.

They are silicone pads. I tried gently w a sharp edge to get them to release, but didn’t want to cause any damage in the process.

Soaking for a day with a small amount of something seems like a good idea!

I have a heat gun that I could try first and see if it does anything.

If all else fails, I’ll get my chisels out and try that :)
Yes, try placing a small piece of wood etc against the top of one device, and tap it parallel to the surface
of the sink with a small rubber hammer. Just hard enough to loosen it, but not enough to move it much
and maybe damage the board from the leads pulling on the pads.
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Why not leave them on, since they are very well attached? At work we irradiated some assemblies that used 'heat transfer gunk' (actually, very nice Dow Corning stuff with 4 W/(m*K) conductivity), and that stuff just didn't budge anymore at all, no chiseling would get things apart (without breaking them) after 11 MGy (quite a bit of radiation). But thermally everything performed just as new. So, I would leave good enough (attached) alone.
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I would happily leave them in, but I have to figure out what the issue is w the amp. Can’t access the circuit board without removing the transistors from the heatsink. I would rather not de-solder all 10 of the transistors on each side to be able to get to the bottom of the board.

I’m getting 82vdc on the speaker terminals. Have to figure out what is causing that. Strange thing, is it’s happening on both channels. The power supply, while a bit high, is not out of the norm for what I’ve seen some people get on the b+/b-. I want to check the trim pots to see if they may have gone bad, and need to pull them to do that.

I know it’s not a good idea to check transistors when they are in circuit, so would like to pull one to see how it measures. I checked them, and emitter resistors in circuit - which is not ideal - and they are all reading exactly the same.

Just want access :)