Below is a number of pictures taken by Dietmar, VE3CG, related to the ICOM IC-746PRO Dead TX Issue, during his installation of a heat sink on IC151 and also two pictures taken from his ICOM IC-756 and the µPC1678G.
Re-routing the cables before the installation.
Location of IC151, the µPC1678G and heat shrink tubing installed over L3 and L4 to prevent possible shorting of heat sink.
IC151, µPC1678G, with thermal compound applied. Keep in mind that the compound does not cool any device it only provides conductivity, i.e. the right amount is better than to much.
If you do not have thermal compound at hand take half a drop from the top side of the radio.
The heat sink.
Two pictures of the µPC1678G and PCB around it as found in the IC-756.
Bo, OZ2M, www.rudius.net/oz2m