Don't laugh, but I have a Dell Optiplex GX280, built in the mid 2000s. I put a GeForce 210 graphics card in it with a 400w power supply in 2012. That power supply bit the dust recently and I decided I would buy a whole new computer this coming Christmas. I just bought the 650w Supernova G5 to use in the GX280 in the meantime (so I can use the graphics card), planning to move it to the new system when I build it.
I installed the G5, got everything plugged in and plugged it into the wall outlet. When I flipped the power switch on the PSU, after a few seconds the CPU fan came on full speed and the power button on the front of the case lit up amber (on an Optiplex, that indicates a power supply problem, pressing it does nothing obviously). I unplugged all cables and plugged it all back in and got the same result. I took out the G5, took out the graphics card, and put the original PSU back in. It boots normally like that so I know nothing was damaged.
I tested the G5 with the self tester that came with it and the fan comes on like it's supposed to.
My question is: Is this most likely a compatibility issue with the CPU fan speed controller? Or is it more likely a problem with the PSU that the self tester can't diagnose?
Thanks in advance.