[Wendymott]

Hi Peeps.. I am sure this has been discussed before, but.....I have just built a HF SSB Linear Pa. Supposedly 180W....This module kit has 2 X IRFP250N devices, but as usual they do not supply heatsinks etc. I built an assembly.. see photo, and included a fan for good measure. However..to isolate the devices from ground I used those grey plastic/rubber/whatever pads.
Do I still use the white compound as a thermal interface or should these be left clean ?.
I have had to do a rebuild as in test a couple of days ago, the PA went S/C.. one Fet went S/c the other O/c. I was probably over driving them from my TX. I am going top reduce the supply from 13.5V to 12.5v in case it was an over volting problem,
I bought replacement devices from Farnell so they should be ok.
Your views would be most welcome.

Sorry Mod.. Maybe I should have put this in.. Homebrew.. Please move if you wish