Question PC does not turn on - No power seems to be reaching the Mobo

May 21, 2022
Hello, first time poster, apologies if this is not in the correct location for my thread.. I am at my wit's end with this problem and would love if someone could help me.

Few days ago my pc clock was falling behind, I read online that this is most likely the CMOS battery running low / failing. I decide that I was going to replace it that night. When I turned my pc off however, the pc stayed powered. There was no display on, lights inside the pc were on, even the components. I was unable to turn the pc off by holding the switch - I held it down for a good while to make sure. In the end I turned it off via the switch at the back of my PC.

The next morning when I came to turn my PC on, it would not start. I got Zero reaction from the pc when I pressed the Power Button. I thought maybe the CMOS battery was still the culprit so I replaced it, but no change unfortunately.

I thought maybe my power switch was broken so I decide to try and jump the pc on via the power pins and a screwdriver, but still no reaction from the pc.

Next I decided to try using a different PSU that I knew that worked, my girlfriends PC was using it just fine, however using her PSU there was still no reaction.

I had an old Mobo that I upgraded from recently that fits my components so I swapped everything over to the new mobo. Still no power, even with trying to jump it with a screwdriver.

I removed the RAM, GPU and all USB devices in both mobo tests and PSU tests but no change. I have not yet tried removing my CPU as a test as its an expensive cpu and I do not want to keep taking it out and risk damaging it (I assume a faulty cpu would not cause a no power situation).

My power cable is plugged directly into the wall and I have tried different cables.

PSU - RM 850 (also tried with RM 650)
Mobo - B550 Tomahawk (also tried B450 Tomahawk)
GPU - Gigabyte 2080 Super
CPU - AMD Ryzen 9 5900X Twelve Core 4.8GHz (Socket AM4)
RAM - Corsair Vengeance RGB PRO 32GB (2x 16GB) DDR4 3600MHz
Cooler - NZXT Kraken x63

If there is anything I have missed out please let me know :)



Retired Mod
Did you swap out the cables when you swapped out the power supplies?

Are these ACTUALLY RM models, both of them, with neither of them being RMx or RMi?

Have you tested the PSUs for power with a paperclip and/or volt meter?

It might be prudent to remove everything from the case and using minimal hardware, test it on the bench/table/countertop etc. with a piece of cardboard or the box the motherboard came in beneath it.