Question about PS_ON and PS_OK

[ajhoward]

I am having issues with my pc, the PSU is clicking repeatedly on and off at startup when cold and trying to troubleshoot the issue.

It only happens when it is cold so I am waiting until tomorrow morning when it plays up and am wondering if it is the case that the PS_ON signal is oscillating, would this be a MB issue since the signal comes from the MB or could this be caused by the PSU or PSU/MB incompatibility?.

The PSU in question has been tried in the morning in another PC and it worked fine.

Also what effect would PS_OK oscillating or incorrect state cause, no boot or boot loop?

 

[ajhoward]

Well, I used my oscilloscope to check the PS_ON and PS_OK and they are both changing state as they should be.

The PS_OK only goes high after the clicking has stopped, powers off and starts properly.
So I tried the PSU in another PC and tried booting up the PC this morning and it started fine but it is a intermittent thing so I set it up in the garage by itself with a paperclip and a HDD for a load. Ill keep trying it to see if I can get it to play up. If it doesn't I guess I'll have to connect it to the original PC again and check the voltages are correct while it plays up?

I can't RMA it unless I can prove its faulty and that the MB isn't at fault. Does anyone think it is likely to be the MB or definitely the PSU?