My biggest suspects - in order of possibillties are:
1) bad thermal switch (so as not to overlook the obvious)
2) bias resistor is going bad
3) final is about to take a dump - or it has and you are seeing just the driver output on the meter
4) not enough thermal paste.
I think that if you can hear the fan when TX'ing -and the mic gain is all the way down- then some part on one of the boards must have become microphonic. A sure sign of a part ready to go bye-bye...
1) bad thermal switch (so as not to overlook the obvious)
2) bias resistor is going bad
3) final is about to take a dump - or it has and you are seeing just the driver output on the meter
4) not enough thermal paste.
I think that if you can hear the fan when TX'ing -and the mic gain is all the way down- then some part on one of the boards must have become microphonic. A sure sign of a part ready to go bye-bye...