I used a psu tester on a new psu and noticed that the -5v pin has no output. My new MB and CPU, which are connected to this psu, are not working (no video output) and the CPU cooler gets extremely hot. Can the faulty psu cause this? I used another good psu and the cpu cooler didn't even get warm (but still no video).
I then put the cpu and the good psu on another new MB (this one has built in video) and I still don't get a video output. I am expecting now that the CPU got bad. Probably from the extreme heat and bad psu. Would that make sense?
-5v was removed from the ATX spec starting with ATX 2.0 if memory serves, which was about 7 years ago. It has not been used in many years. That is only on your tester to test older PSU's. Don't worry about it.
If the -5v pin is not used then it's another problem which is casuing the MB not to work.
The PSU tester indicates the psu is good. It's brand new. I had two older psu's which lit the -5v pin and when I didn't see that on for the new psu, I thought it was a bad psu.
The -5v is missing on modern power supplies as it is not needed by modern motherboards and nowadays you are unlikely to come across a motherboard that requires this voltage if the power supply is used to replace a faulty one in an old system.