I can confirm that the 40x15mm PSU fan is connected to a (seemingly low voltage) PCB via a connector and physically screwed to back of the housing. Replacement would be easy. That being said, I would advise against replacing it because:
- Risk of injury or death.
- Loss of warranty.
- The PSU is densely packed, the fan needs to have a high static pressure and there seem to be no obvious choices for a different fan.
- A different fan might not match the control logic, leading to possible higher temperatures.
- The PCB that controls the fan might also be the one that signals a power cut, in case the temperature gets way too high. I would not mess with a safety circuit that is designed to prevent damage or fire.
- With Framework replacing PSUs, sending them to repair centers and back to Taiwan suggests that the fan does not behave as designed and we will see a solution in the future.
I got my idle power consumption down to about 6-7W (APU reported) with the PSU fan running maybe once an hour (and of course during/after load). I’m still looking forward to a proper solution but I can live with it for now. Otherwise, I would attach a small fan to the back of the PSU instead of messing with the internals.