How to unstick transistor?

I am trying to replace the output capacitors in my KEF 30b subwoofer amplifier. I cannot get to the under side of the capacitors as the circuit board is connected to two transistors that seem to be stuck to the heat sink? Any ideas on how to unstick these?


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Put a few drops of iso alcohol, will reduce the adhesion of dried heat sink compound.

Then a tap with a strong knife, or aluminum / wood block to chisel made of power hacksaw blade, at the edge of the transistors to pry them loose.

Those blades are 400 x 25 x 1.6 mm, I get broken / old ones from a friend.
Quite suitable for this type of work, you can spread out the force.
Less chance of device damage.
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The reason they were stuck in the first place is because they did a good job of properly applying heat sink compound. Properly done, the surface tension is strong and it’s a bitch to get apart - even with fresh compound. Youre not supposed to use a lot of it - it’s a mistake many builders make.
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So next question, what do I use to stick them back down?
Thermal compound (aka thermal grease). Wakefield 120 or 126 is what I use.

Youre not supposed to use a lot of it - it’s a mistake many builders make.
Exactly. You're only supposed to fill the voids between the transistor package and the heat sink.