PC suddenly shuts down

MC23 · March 30, 2021

Hello everyone, as the title says I'm having a problem with my PC suddenly shutting down.

PC SPECS

MOBO: ASUS Z97-Pro Gamer

CPU: i7-4790k @ 4.20 GHz

Liquid Cooling System: CM Seidon 240M

Video card: MSI GTX 970 (now dead, I think)

PSU: Corsair RM750

HDD: Western Digital Green (2x2TB)

SSD: Samsung SSD 850EVO (1x250GB)

RAM: 2x 8GB Corsair Vengeance @ 1600 MHz

OS: Windows Pro x64 (original)

All components are ~8 years old

PREMISE

Some weeks ago my PC suddenly shut down while I was watching a movie. It shut down, then quickly turned on and off again a couple of times before definitely shutting down. Some burning smell came out of it, so I unplugged every cable (without removing any component) but I couldn't be able to identify where the smell came from.

I then plugged the PSU back in and hit the on/off button, with no response. However, I noticed that the mobo spy was on. I proceeded with the paper clip test, without loading the PSU (since I didn't have any converter to plug a fan) and it didn't turn on. I then proceeded with unplugging the video card (removing it from the slot too) and SATA units, and I was able to boot successfully (I plugged the monitor to the integrated video card via VGA). I then plugged the video card back in and I wasn't able to turn on the PC, and according to a Discord user that helped me troubleshooting all of this, the conclusion was that "the video card external power is shorted". So, even if I was sad about the loss of my video card (the aforementioned GTX 97), which actually smells a little burnt, it was okay because I could use my PC for my daily activity.

PRESENT DAYS

For a few weeks I didn't have any problem but lately it happens that the PC suddenly shuts down, and turns on again without me having to hit the on/off button. Sometimes it takes some seconds to turn on again, sometimes I have to move/shake the case for it to happen (NOTE: little case shakes, for examples when I accidentally hit the desk, can also lead to the PC shutting down, but I'm not 100% sure about this). When it reboots, I get a "Power supply surges detected during the previous power on, ASUS anti-power surge was triggered to protect from unstable power supply etc...".

Other things I noticed, that probably don't have anything to do with this:

before shutting down, I usually hear a loud fan noise, this would be my CHA_3 fan (one of the two CM Seidon fans, which starts working only when the CPU reaches 60° C according to my). The loud fan noise is not recent, and that's why I set it to only activate at that temperature.
so far the PC never shut down while my mum was using it using her account, even after a long period of time. Same thing for when it is in the BIOS screen.

So here are my questions:

is disabling the power surge protection reckless in this case?
how can I be sure that the my PSU is the problem? Couldn't it be some cable that gives I don't want to buy a new PSU just to discover that it wasn't the problem. I don't have any tool to verify the voltages , and I don't think I'd be able to do that on my own since I don't know much about the subject.

Here's a picture of the BIOS Voltages:

https://imgur.com/lBZwPUE

Thanks in advance!

PwnyTheTiger · March 31, 2021

4 hours ago, MC23 said:

"Power supply surges detected during the previous power on, ASUS anti-power surge was triggered to protect from unstable power supply etc...".

That pretty much says it all, and what the problem more than likely is...

MC23 · March 31, 2021

8 hours ago, SGT-AMD said:

Check all fans including the psu fan for dust and dirt. Opening a psu can be dangerous, so it would be good to check around on the internet for instructions on doing that.

Usually, a computer will re-boot itself because of low voltage coming from the psu, going to the cpu, as they are designed to do that, and you end up with a loop (sometimes).

Okay, I will look for some guides on how to do that. I cleaned all the other fans when I unplugged everything some weeks ago.

7 hours ago, PwnyTheTiger said:

That pretty much says it all, and what the problem more than likely is...

Hello, I read that sometimes the ASUS setting is "too sensitive" and that the error can be given wrongly, this is why one of my questions was "is disabling the power surge protection reckless in this case?": according to what I read (on different topics, not only one) if you disable it, the PSU protection should still be active (I'm pretty sure this depends on the PSU, but I don't know how the feature is called to check if mine has it) so the components wouldn't be at risk. Then, if the PC still shuts down that's a 100% sign that the fault comes from the PSU. Is this statement correct?