Question Computer turns on, but monitor keyboard and mouse won't

[Sipan9000]

I built my friends computer about a year ago. It's been working perfectly fine since then, but today he told me that he left his house and left the pc on (sleep disabled) and when he came back a few hours later it was still running, but the keyboard, mouse & monitor wont turn on, caps lock wont light up on the keyboard when pressed either. We tried unplugging from the rear, pressing the power button a few seconds, waiting a few minutes then plugging back in, but nothing worked. Weird thing is that another friend of mine asked me to help him a few days ago & he was experiencing the same issue. From the research I did, people said it could be psu, motherboard or ram, but now I'm not so sure. Anyone dealt with this before or have any insight?

Specs
x570 strix
r7 5800x
rx 6900xt
samsung 970 1tb ssd
evga 850w gold psu
windows 10
trident z 32gb ram

 

[Colif]

It sounds like the PSU isn't supplying enough juice to run all the "extras" at start. If it lacks power it can turn USB and monitor off, to conserve it for the CPU.

are the specs below the PC in question or yours?

How old is PC?

Only real checks for PSU are:
the paper clip method - https://forums.tomshardware.com/threads/what-is-the-paperclip-method-of-testing-a-psu.1336402/ - this just checks it turns on, we know that.
or multimeter https://www.lifewire.com/how-to-manually-test-a-power-supply-with-a-multimeter-2626158
or in the BIOS to check the +3.3V, +5V, and +12V. - https://www.lifewire.com/power-supply-voltage-tolerances-2624583 - not as useful as multi meter. Not helpful if screen doesn't work.

 

[Sipan9000]

The specs are for the pc in question, it's around a year old. When it happened to my other friend a few days ago we thought it was the power supply too, but after replacing it, the problem persisted. I just saw a video on youtube with a guy having the same problem, he said that removing the reset cable in jfp2 worked. I don't know how that would work though.

 

[Colif]

it could help if the case cable is the problem I guess.

You might want to breadboard it, take it out of case and see if it starts with bare minimum attached.

How To - Breadboarding, stripping it down to the basics for troubleshooting

If you have to read this, something is very wrong with your PC such that you need to fully troubleshoot your system at the most basic hardware level, Breadboarding. A little background: breadboards were what we called our lab equipment in electronics school. I don't know why they started...

forums.tomshardware.com

 

[Sipan9000]

it could help if the case cable is the problem I guess.

You might want to breadboard it, take it out of case and see if it starts with bare minimum attached.

How To - Breadboarding, stripping it down to the basics for troubleshooting

If you have to read this, something is very wrong with your PC such that you need to fully troubleshoot your system at the most basic hardware level, Breadboarding. A little background: breadboards were what we called our lab equipment in electronics school. I don't know why they started...

forums.tomshardware.com

Didnt work unfortunately. Went and bought a new psu, motherboard and ram. Still not working, could it be the cpu? Speaker on motherboard wont beep any codes either