Testing a PSU and need to ask for some advice.

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AlbusDlx

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Dec 25, 2011
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Hi. I have borrowed a PSU to test in my brother in laws PC. His psu is dying and I just want to make sure that is the case before I recommend buying a new one straight away. So before I do this I wanted to measure it with my voltmeter. So I shorted the green and black to start it up. Hooked up an old powerhungry HDD I dont use and a fan.
The 3v and 5v seems ok. But the 12v reads at 13.3v on all cables, molex, sata, MB 4pin and so on.
Can this hurt his PC and is it stupid to try it under real conditions where his PC might get hurt in the process?
 
Solution
C12Friedman
13.3v is out of specs for a PSU (must be +/- 5% on positive rails). Although probably not as bad for components as a PSU that doesn't supply enough current, overvoltage does put some big stress on your motherboard and other components and some components (fans notably) will burn out quick. I would say it would lead to premature aging of everything it's connected to.
I'll suggest checking the capacitors on his motherboard and looking for burns or discoloration on any FETs since those are what takes the brunt of overvoltage. Depending on the motherboard, you may need to remove a heat sink over the VRM to check those. If the heat sink is removed, any thermal compound should be replaced with fresh compound.
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Quarkzquarkz

Quarkzquarkz

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Sep 18, 2013
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Green wires usually signal power up voltage and aren't really necessary. 12v are yellow wires and shouldn't read on all cables like that. The only time you can hurt your PC is if you accidentally short 2 with 1 lead and try to measure another, and/or have a static charge without properly discharging yourself with a bracelet, or just sticking voltmeter leads into pins you aren't familiar with. Just be diligent and cautious and you shouldn't have any problem with measuring under real world conditions. Good luck!
 
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C12Friedman

C12Friedman

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Jan 25, 2012
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13.3v is out of specs for a PSU (must be +/- 5% on positive rails). Although probably not as bad for components as a PSU that doesn't supply enough current, overvoltage does put some big stress on your motherboard and other components and some components (fans notably) will burn out quick. I would say it would lead to premature aging of everything it's connected to.
I'll suggest checking the capacitors on his motherboard and looking for burns or discoloration on any FETs since those are what takes the brunt of overvoltage. Depending on the motherboard, you may need to remove a heat sink over the VRM to check those. If the heat sink is removed, any thermal compound should be replaced with fresh compound.
 
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