Richard R Posted May 17, 2021 Share Posted May 17, 2021 Evening all, I'm replacing a couple of damaged input sockets on a friend's Fender 85 amp, nice easy soldering job, no high voltages. As you can see from the photo, taken before further disassembly, there are two amp chips firmly bonded to a piece of aluminium. This is attached to another thicker block (which isn't visible), bolted through the aluminum back plate of the housing. (Which is labelled "warning gets hot in operation", or something like that). So the metal back plate, thicker block, and visible aluminum comprise the entire heat sink. I had to remove the back plate and block to get to the solder side of the circuit, and noted thin tranparent grease between each layer. I assume this was thermal paste, but all the paste I have used has been white, more like that visible on the chips. So the question is, is there a minimum spec or recommendation for thermal paste to use when reassembling? I have a little tube suitablebfor CPU heatsinks, but I think something better is required? This is an 85W amp. Many thanks, as ever. Quote Link to comment Share on other sites More sharing options...
paul_5 Posted May 18, 2021 Share Posted May 18, 2021 That looks like it’ll be fine; operating temperature up to 240 degrees C - the solder on the boards would melt at just over 200! 1 Quote Link to comment Share on other sites More sharing options...
Richard R Posted May 18, 2021 Author Share Posted May 18, 2021 Thanks. I know pastes come with different W/m^2/⁰C ratings, so that was my main concern. Quote Link to comment Share on other sites More sharing options...
paul_5 Posted May 18, 2021 Share Posted May 18, 2021 Your TIP147 power transistors will only run to 150 degrees C anyway. Quote Link to comment Share on other sites More sharing options...
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