PSU Repair process

[alizadeh.turkel]

Hi All,

I have a 2 broken PSUs one 500W other is 250W, I am trying to repair them. I have replaced all capacitors within both PSUs and it passed voltage output test too. But none of them still not working. When I start the motherboard only fan is running and not light, beeps, video etc.
Which component should I test next if the issue is not capacitors ? Can the MOSFETs or any teroids burned ? how can I test them without removing out by multi-meter.


Regards,
Turkel.

 

[turkey3_scratch]

How do you know the PSU is broken and not some other piece of hardware like the motherboard?

 

[alizadeh.turkel]

Sure by testing with another working PSU

 

[InvalidError]

If a MOSFET was dead, then either the outputs would be grossly out of specs or some other part of the PSU's circuitry would self-destroy.

If your multimeter has a min/max function with decent bandwidth, you may want to try recording the min/max on each rail. Having the correct average output is pointless if it overshoots and undershoots well out of bounds. Also, if you measured voltages only while unloaded, you may want to check again with the motherboard and whatever else plugged in, behavior could be quite different with other stuff attached.

 

[alizadeh.turkel]

My mutimeter dont have such function, any other way to test min max? I know ocsiloscope required for this I will try to build ocsiloscope with my arduino and test output, but it will take some time.

I have tested it on load too, the only pin Blue shows 11.68v which seems a bit out of range.