Faulty power supply?

[Hamzter]

Hey,

I built a new system last week, it worked perfectly for 24 hours but shut itself down while i was out and wouldn't reboot, the fans spin but nobody's home! I did the usual checks and disconnected everything I didn't need and sat the mother board on my desk, same issue. Eventually I swapped out the PSU (Corsair CX500) with an old 300W one I had kicking about and it booted up fine, so I concluded I had a duff power supply, however I've just tested the new psu with a multimeter to find that all the voltages are within spec, so now I'm not sure if it's the psu or motherboard at fault. I got the following voltages with power running to the motherboard and hdds...

+12v was 12.44v
+5v was 5.00v
+3.3v was 3.36v

The 12v line looks a bit high but still within spec (max 12.6v), anyone have any clue why it won't start? Specs are...

Corsair CX500 PSU
Gigabyte GA-H61MA-D2V motherboard
Intel i5 K3570
16GB Crucial Ballistix RAM

Thanks for any help

 

[ConnorJoshua]

if the 300watt worked but the CX500 doesn't, then it would seem obvious that the powersupply is duff. Try running the 300 watt for a while to rule out other components

 

[Hamzter]

It was possible that it was just the motherboard being fussy with voltages so it could have been either. After a bit more reading I realised there was one more pin called pwr_ok, this is a pin that outputs 5v when the psu decides the voltages are in spec and stable, it only gives out 0.11v though so it looks like the internal psu logic is shot, time to RMA it. Tanks for your help anyway