I picked up a used Adcom GFA-7500 five channel amplifier a couple of months ago. Upon inspection, I was able to see that one of the amp modules had been repaired, but the person that did it seems to have cut some corners.
In particular, I could see the repaired channel had thermal grease applied between the transistors, AND the original thermal pad. Thermal pad is all that is used on the original, unmolested amp modules. Upon further inspection, a chunk of used thermal pad was added to try and fill an area where the original thermal pad was torn (see the attached photo).
I had to take the amp module apart to replace some incorrectly sized capacitors on the "repaired" channel anyway, so at this stage I'd like to mount it to the heat sink with new thermal pad.
My question for the experts here is what type of thermal pad should I use? When I search on Digi-key I see a wide range of products made from different materials and different thermal conductivity. Any suggestions would be appreciated.
In particular, I could see the repaired channel had thermal grease applied between the transistors, AND the original thermal pad. Thermal pad is all that is used on the original, unmolested amp modules. Upon further inspection, a chunk of used thermal pad was added to try and fill an area where the original thermal pad was torn (see the attached photo).
I had to take the amp module apart to replace some incorrectly sized capacitors on the "repaired" channel anyway, so at this stage I'd like to mount it to the heat sink with new thermal pad.
My question for the experts here is what type of thermal pad should I use? When I search on Digi-key I see a wide range of products made from different materials and different thermal conductivity. Any suggestions would be appreciated.
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The grey thermal pads do not use thermal paste as they are soft. Paste reduces their efficiency.
The sky is the limit, TO220 is the smaller size and TO3P the larger. Fibre glass silicone rubber is excellent. http://uk.farnell.com/bergquist/sp900s-0-009-00-104/sil-pad-900s-009-to-3p-pk10/dp/8783578
The sky is the limit, TO220 is the smaller size and TO3P the larger. Fibre glass silicone rubber is excellent. http://uk.farnell.com/bergquist/sp900s-0-009-00-104/sil-pad-900s-009-to-3p-pk10/dp/8783578
Thanks Jon. I understood thermal paste should not to be combined with thermal pad. The original material is the off white color, and there is no paste where it is used on the other modules.
I have a sheet of this material: https://www.mouser.com/ds/2/223/THR-DS-Tflex 200 V0 0710-1134500.pdf
I see that it's thermal conductivity is on the low side at 1.1 W/mK, so I started to wonder if perhaps I should use something better.
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