Dead PC - Suspect Motherboard

[TonyMan]

PC died after a power outage, but under strange circumstances. I feel I've troubleshot it down to the motherboard, but would appreciate a second set of eyes before I run out and buy a motherboard in case there is something I missed or more steps to try.

Here is what transpired so far:
Lost power, UPS kept PC running
Shut down PC, then UPS
Power on, PC won’t start.
Moved PC to another outlet for testing
Jumpered 16 & 17 on PSU 24 pin connector, PSU fan & light work
Verified all voltages voltages OK on 24 pin connector
On/off switch shorts when pushed
Reset switch shorts when pushed
Jumpered on/off, won't turn on
Jumpered reset, won't turn on
Disconnected small plug from modular PSU to see if it was causing a problem, won't turn on
At this point it sound like motherboard is bad

System
MSI B450-A Pro Max AMD AM4 ATX
Ryzen 7 5700G
C drive - Samsung 980 PRO 1TB
D drive - Samsung 970 EVOPlus 500GB
PowerSpec RGB 650 Watt 80 Plus Bronze ATX Semi-Modular Power Supply

Any thoughts or ideas appreciated.

[Midknyte]

If you have a known-good PSU, test with that first. Might as well do that before you pull out the motherboard.

You could also reseat the RAM, and remove any PCIe cards except for video.

[Steve R Jones]

Moved PC to another outlet for testing

Is it safe to say you did this test withOUT the UPS?

[TonyMan]

1. As fast as a spare PSU, when not connected to the motherboard it turns on and I tested all voltages with a voltmeter. I’ll go ahead with pulling PCIe boards and resetting RAM.

2. Yes, all tests were done from a wall outlet, the UPS wasn’t involved.

Thanks

[TonyMan]

Ok, I resented the RAM, no difference.

I pulled out the two PCIe cards, no difference.

I even tried pulling the modular plug for PCIepower, no difference.

Looks like I’ve going to head to Microcenter when they open and get a motherboard.

[TonyMan]

BTW, I also pulled the small modular plug that supplies PCIe and SATA power just to insure nothing on that leg was holding the PSU down. The PSU, still wouldn’t turn on.

[TonyMan]

My son did have an old PC with a PSU. I pulled it and see that instead of a 4x2 connector like I have near the CPU, this has a 2x2 connector. I still plugged in the 24 pin connector, gelling I just wanted to see the fans start. Still no good.

Going for a new motherboard.

[TonyMan]

Up and running with the new motherboard. Still confused over why the old one failed. But the good news is a new motherboard and back in business.

[Steve R Jones]

There could have been a Power Surge before it went out.

Glad you got it sorted.

[TonyMan]

Thanks

[europanorama]

Dying PSU or weak one could damage MoBo. In my case June 2018 ontop came capacitor plague. Which MoBo was it?.- Mine were soon after 2000. 2004. after 5000 hrs capacitors dying instead of 10000. nowadays 10k reached sooner. depends the use.
Which Windows used?
good if one has a second similar pc to test parts. and having spare-parts- PSU, videocard, Ram, cables and hdds.
cleaning the contacts from time to time helped tremendously solving problems. also under sata-hdd motherboard. which i wasnt aware of.