Corsair RM850x Synchronous ATX PSU - need help diagnosing

[W1ngl3t]

Hi all,

I have a relatively new (from 2018) Corsair RM850x PSU that refuses to turn on.
The 5v standby rail is working fine, but when I try to turn it on it shuts itself off in a few milliseconds.
There are no obvious shorts to be found and this is what I can see with my oscilloscope:
- 3.3v and 5v hold their intended voltages fine for a few millisecond
- the 12v rail goes to 12v on startup and then goes into decline
- when the 3.3v and 5v rails are switched off the 12v rail momentarily increases a bit (probably perfectly normal)
- as per the datasheet, the overcurrent protection (OCP) is triggered when the OCP sense pin voltage exceeds 1v. As per my measurements, there are a few spikes above 1v but this is probably just noise?!

Any ideas as so what the problem might be or what I should be checking?

Thanks for your help!

[Francesc V.]

Maybe a cold join in a coil might cause it............have you been able to progress in the troubleshooting?

[CapLeaker]

That's happening because the supervisor IC WT7502 is shutting it down. If you want, you can force the PSU on (protection is disabled) and then you can troubleshoot.
Attach some clear, straight shot, high resolution pictures from the PSU.