My latest lockdown project was adding a fan to the linear power supply in my shack.
When I did a long run of CW QSO’s at 100W, a strange smell started coming from under my desk … in case you readers have any doubt, the smell came from the PS ! 
I found a very simple circuit here
I took a 10k NTC resistor (there is one in every laptop battery pack, they look like two thin wires with a “drop” of plastic at the end), and a 10k multiturn trimmer (not 50k).
The FET used was an IRF830, but I guess any IRF 5xx will work just fine.
The FET was mounted on a heatsink, but it never gets warm, so it’s probably overkill.
I still have to find a small box to house the circuit.
I didn’t want to drill holes in the heatsink or anything (and being lazy …), so I simply mounted the fan with some heavy house wiring (2.5mm²) which I shoved behind the heatsink. I made some zig-zag in the wire to make it sit firmly.
The NTC is also just hanging between the heatsink ribs.
I adjusted the trimmer so that the fan is OFF when the PS is switched on.
When I run my IC-7300 in RX for a while, drawing 0.7A, the fan comes on very slowly. Speed increases as needed, but it never makes any noise.
The PS stays much cooler than before.
Oh yes, and if there is a smell now, it must have some other source … 
At the same time, I made a “quick and not so dirty” 4-way PowerPole splitter on the front.
73,
Luc - ON7DQ