Question PC Won't Boot - Bad motherboard or CPU?

[Jabber92]

Hi all,

I recently built a new system and had it up and running for around 2 days and it seems to have died, after working on 2 occasions. First, I'll post the spec:

Motherboard: MSI MPG Z690 Edge WiFi DDR4
CPU: Intel i5 12600k
GPU: Sapphire RX6800
RAM: Corsair 32GB DDR4 3200Mhz
PSU: Corsair RM850e Gold 850W

So let me breakdown the process:
1) Built the system fully. Everything plugged in fully. Fully successful boot up to BIOS and did fresh install of Windows 11 Pro. Everything worked fine that night. Shut it down and went to bed. It was on and running perfect for at least 6 hours.
2) In the morning, I power up the PC. It only boots for half a second with Red CPU light flicking on. It keeps trying to boot but simply would not. I take it apart and reseat the main power cables. Afterwards, it boots again as normal. I used it again all day for at least 12 hours. I shut it down for the night.
3) I wake up and try to turn it on. SAME PROBLEM. I take it apart and try the cables again since that fixed it the day before. No luck this time. It tries to boot but immediately shuts off in 0.5 seconds like before. It was working perfect just hours before.

So now I'm stuck at the boot loop. I've taken it out of the case and have only the motherboard and CPU plugged in on antistatic surface. No RAM or GPU. I've tried 2 power supplies. I've double and triple checked the cabling and all it will do is flash the CPU light for 0.5 seconds and keep trying to boot over and over.

Could the motherboard just die suddenly like this? Could the VRM from PSU to CPU have died or bad MOSFET? I feel if the CPU was bad it never would have booted from the beginning or the 2nd time. I have another motherboard coming this week, but in the meantime I'm willing to try other ideas. Thanks for any help.

 

[DaleH]

Yes, new things can die too (infant mortality). CPU could have died and motherboard, as well. It could have failed after one or two tries. Suspect you'll have to wait for the motherboard to arrive.

 

[Jabber92]

Yes, new things can die too (infant mortality). CPU could have died and motherboard, as well. It could have failed after one or two tries. Suspect you'll have to wait for the motherboard to arrive.

Super frustrating! Never had a problem like this before so early on. Usually after many years. Seems like a big drop in quality or I've simply gotten bad luck. I'm really thinking motherboard because it almost seems like it shorted out each time and now it just won't boot at all after working totally fine hours before.

 

[Jabber92]

I diagnosed the problem. There's a pin sheered off in the USB 3.0 header on the board, and it's breaking the initial P1 power phase during the boot up, and so it's going into a boot loop because the circuit can't be completed properly to put power through the rest of the board. I believe when I first re-seated everything, the pin in the header was still there the first time I did. But since re-seating the 2nd time, the stupid USB 3.0 cable strained itself and popped off and broke a pin off with it. I will have to replace the board, sadly. Based off the diagrams, it's not a GND (ground) pin, but sadly a pin part of the P1 power circuit.

On the next one, I am DEFINITELY not installing the USB 3.0 cable to that header again. It's in a terrible spot, I should have known better. Oh well. I didn't think it'd be THAT fragile, but it is.