I made a quiet cooling fan once (not for the Stereo 70 though). I bought a 120VAC pancake fan, advertised as being really quiet. It wasn't quiet enough. I ran it on a variac to see how much voltage I had to drop to slow it down to where it was quiet enough. Then I built a little voltage divider with 5 watt resistors to match the variac results. Works fine. I may put it back in service with my Stereo 70, just to try to help out the original PT a bit.
I also had a suspect can cap that I purchased new about 2 years ago. The can ran a little warm, right from new. The amp always had a touch more hum than I expected it should, though not extreme. Voltages were all reasonably in line with the schematic. But a NOS Mullard 5AR4 only lasted 2 years. :tears: I've since recapped it with essentially stock values stuck under the deck. The new caps stay cool, and the amp subjectively has about half as much hum as before.