In my Naomi uni cab when I power up the fan in the psu runs for a couple of minutes then stops, should it stay on all the time or does it turn back on if it gets hot enough????
If it's really loud the motor could have seized and that's the reason you only hear it for a few minutes. After that it gives up trying to spin (I've seen this before, but in a computer power supply).
simply replace the fan - I replaced mine with a Silent Akasa when the original started getting noisy, I plan to do this on my 2nd Naomi aswell, I hate loud fans