19 July 2010

It's getting hotter...

In a previous post I discussed the problem of imperfect contact between the power amplifier modules and the heat sink in an TM-D710. Last weekend I worked on three more D-710s, which had developed the infamous "withering filter" illness, and discovered that the imperfect contact matter may reach extreme proportions!

Take a look at the photos (click on them to enlarge). The power modules barely made contact with the heat sink, only near the affixing screws. Less than 20% of the surface was in contact! Not a very good scenario for the longevity of the modules!
The other two rigs showed about 25% and 10% loss of contact, and only at one of their two modules, respectively.  The photos are of the "worst case" rig. As an afterthought, I should have tried to see which is at fault, the modules or the heat sink, but I foolishly didn't do that. I will in the next transceiver that comes along, and let you know. My wild guess is that the die-cast heat sink machine finishing (leveling) at that spot is at fault; but  I am certainly not sure.

What to do if your rig suffers this way? A couple of drops of gear oil will probably slide your problems away and cool things off, see the older post.