PC not starting up, only powers for 6 seconds

[Rick Rab]

Power outages and likely surges shorted something, lost ability to boot; no power. Replaced PSU, can't get more than 6 seconds of life out of it. Voltage was unchanged. Everything is plugged correctly, the only thing that was changed was the PSU. Did something else get shorted? MOBO is a MSI X470, the are a couple red lights that come on before the power shuts itself off. Also sometimes after shutting its own power off, it will attempt to power itself on again without user input with the same results. It also tries to auto-power itself after being plugged in.

Things I've tried and extra notes:
-removing all external plugs besides power
-booting with only the motherboard and cpu powered
-booting with one RAM
-all fans are spinning as normal

 

[Bruce]

if old PSU was fried, in my experience it is not uncommon for whatever caused the PSU to die to also continue on to the motherboard.

have also seen mobo's die from power surges that came through the ethernet port as these go back to an earthed modem.

 

[PeterOz]

sometimes a cmos reset/clear can help - see attached

 

[Bruce]

@Rick Rab - you logged in on Thursday but haven't responded.
still need help?

 

[Bruce]

abandoned