This amp is has diode rectifiers and would benefit from a thermistor...Also cathode biased amps run hotter. You may need to change the cathode resistors to draw less current. That said, What a beautiful amp! I'm jealous...
Thanks guys! Unfortunately I don't have much technical understanding of these amps, but yeah - I think that is the thermistor for this amp.
The guy that originally refurbed this for me had put a set of thermistors elsewhere to make the output tubes run a little cooler to help prolong they're life. I'm not sure exactly where this pair was located. When I recently took it in to be serviced the tech removed those since they had crumbled and he didn't see them in the original schematic.
