Question PC turns off, then powers up but doesn't boot

[Linally]

Good Evening!

I have had the pc with the specs below for a couple of years now and never had a problem:

CPU: Ryzen 2600

MOBO: Asus ROG F-Gaming x470

COOLER: CORSAIR H100i RGB Platinum

RAM: G. Skill RGB TridentZ 32GB 3200MHz c14

GPU: GeForce Gigabyte 1080 Ti

PSU: Seasonic Focus PX 650W Full Modular 80 Plus Platinum

Disks: 1x Samsung M2 970 Pro
2x WD Blue 1TB ssd

After 2 years of functioning perfectly, for the past week or so for the past week or so it randomly powers off regardless of what I am doing at that moment and afterwards when I try to start it up it powers on, leds-fans-ram-keyboard etc but it won't boot. It only boots after a period of time that gets longer every time this happens. I tried cleaning both the RAM and gpu, tried booting with single dimm of ram but nothing. I tried switching to a different power outlet and replacing the power cords but still no progress. I checked event manager and other than the kernel error report that comes from the abrupt termination there are no other critical entries. Also there are no temperature issues, most components never got over 45-50C even during gaming. I tried booting without the GPU but it still didn't work so the GPU is probably OK.

Anyone has an idea what it could be? My guess is either Motherboard or PSU, but since it powers up every time the PSU should not be it, correct?

 

[Ralston18]

Do you have a multi-meter and know how to use it? Or know someone who does?

https://www.lifewire.com/how-to-manually-test-a-power-supply-with-a-multimeter-2626158

Not a full test as the PSU is not under load. However any voltages out of tolerance would indicate a failing/faltering PSU.

Test voltages when PSU is cold and then later when the PSU has warmed up....

 

[Linally]

OK, so I don't have a multi-meter and don't think I know anyone that does. What I found was that if I remove the backplate cover of the pc case appears to have solved the problem. It could have been a cable management issue I guess? I have a BeQuiet Dark Base Pro 900 rev.2 case, and all the cables are between the motherboard and the backplate, so something might have been jammed in there. I will monitor the issue to see if it reappears and if so I will look for someone with a multimeter

 

[Ralston18]

Something intermittently shorting out.

Power down and unplug.

Use a bright flashlight to look for bare conductor showing or some metal to metal contact. Perhaps a kinked or pinched cable.

 

[Linally]

So from what I can see no conductor is exposed and no cable seriously pinched. I can't really see the PSU cables well because they are all covered in protective sleeves which I would have to cut in order to check. What I noticed though was that the noise insulation layer on the backplate has an indentation mark at a point, kind of like something was pinched between that place and the mobo backplate. Could be a cable was riding on the LED controler module and I didn't notice before. So far the pc has not restarted either during gaming or at any other point, so this should have been it.