Question PC "crash" even when OFF ?

[Umpire]

Hi there, good people,

TL;DR version:
my PC randomly crashes. Under load, in sleep or even when shut down (no shutdown for fast startup or whatever Windows calls it either, good old shutdown). It looks like somebody pulled the cord, but USB lights are still ON.
To make it work I need to flip the I/O switch on PSU (or really pull the cord) and wait until all power is drained and then all's well for few days or even weeks - or hours .
Could it be bad PSU or mobo? Or something else?

Longer version:
In past few months I've been having a problem with my PC. All parts are ~2 years old, except for the case, some disks and peripherals. It's randomly shutting down. I guess it's not random, but I can't figure out what could be the cause.
So far I've come to the conclusion that it's something wrong with circuitry of PSU or mobo.

The symptoms are simple. It just crashes as if you pulled out the power cord. Everything turns off, nothing reacts, not even the ON/OFF button to start the PC again. Surprisingly, the devices connected to USB still get power because my headphones got some LED lights and those remain ON.

It doesn't happen only under load (I think I got couple crashes when playing games) but it's at any time. When idle, when working wia RDP, when just browsing net, when the PC is at sleep and, and this is interesting, when the PC is powered OFF. Ha! Now WTF?

I tried disconnecting all USB devices, so those don't affect it. I'm ruling out disks, GPU, RAMs etc. because it happens even when PC is OFF - but connected to power. All that's left is mobo and PSU. I'm thinking one of them or both are faulty.

I'm an inch away from trying to flash BIOS to new version but the vendor says "Don't update unless you have issues." Sure, I got issues, but is it mobo issues? All devices are OK, so maybe BIOS update won't help and I try to avoid making even bigger mess.

I got the PC connected through one of those surge protection things, so I tried connecting it just to power outlet, then to a different outlet. Didn't help.

It's pain in the ass to "debug" because I can't reproduce it on demand and it may be over a week or more before next crash.


So, now I'm looking for someone smart, knowing things electrical about PC HW to tell be what I could try next or that these issues are common when ... .

Mobo and CPU are just beyond warranty and PSU and GPU have 2 months left, so last resort is trying to replace it under warranty, but I'm trying to avoid being without PC for a month until the warranty stuff is sorted out, becuase there's a high chance that they tell me to sod off cos' they haven't found anything wrong with it.

Many thanks for any kind of help.


Here's the specs:
PSU: EVGA SuperNOVA 750 GT - 750W
Motherboard: ASRock B450M Steel Legend - AMD B450
RAM: 4x Corsair Vengeance LPX Black 8GB DDR4 3600 CL18
CPU: AMD Ryzen 5 3600
GPU: Sapphire Radeon PULSE RX 5600 XT 6G, 6GB GDDR6
Disks:

• system: WD SSD Blue SN550, M.2 - 1TB
• other: WD My Book 1140 (USB), WDC WD1001FALS-00E8BO, MTFDDAK512MAY-1AE1ZABHA

 

[Colif]

Could it be bad PSU or mobo?

windows can't be the cause if it crashes when its turned off and Fast Startup is off, if it happens after sleep it could mean its PSU.

How do you know it crashes when its off as there can be no errors. Do you mean you still have the power issues regardless.

its likely PSU or MB although they not the easiest parts to test
PSU tests

1. the paper clip method - https://forums.tomshardware.com/threads/what-is-the-paperclip-method-of-testing-a-psu.1336402/
2. or multimeter https://www.lifewire.com/how-to-manually-test-a-power-supply-with-a-multimeter-2626158
3. or in the BIOS to check the +3.3V, +5V, and +12V. - https://www.lifewire.com/power-supply-voltage-tolerances-2624583

2 is the best way, 1 only checks it works and 3 only shows it at idle.
Not many people have 2 though.

No real tests for Motherboard, you test everything else like you have and use a process of elimination. Or you take PC to a store and ask them to check everything and let them tell you. 2nd opinions always helpful.

Could be something else, could be a CPU problem... why I don't like guessing.

 

[DRagor]

Generally speaking in cases like this it is most likely PSU problem. However there is one thing you are missing - Power button. Faulty Power button might cause both problems you described (sudden power off/no power on). So first thing to do is disconnect it from motherboard and use screwdriver method to start PC. If that makes no difference in your PC behavior then next step is try different PSU.

Btw, you mentioned parts are 2 years except case. Another thing that potentially make this problem is short caused by case. So it might be worth to rebuild the system outside of case. Although that's a lot of work so if you can obtain different PSU easily I would rather do PSU swap first and only if that won't help do the rebuild. If nothing above helps then it's time to change motherboard.

 

[Umpire]

windows can't be the cause if it crashes when its turned off and Fast Startup is off, if it happens after sleep it could mean its PSU.

How do you know it crashes when its off as there can be no errors. Do you mean you still have the power issues regardless.

its likely PSU or MB although they not the easiest parts to test
PSU tests

1. the paper clip method - https://forums.tomshardware.com/threads/what-is-the-paperclip-method-of-testing-a-psu.1336402/
2. or multimeter https://www.lifewire.com/how-to-manually-test-a-power-supply-with-a-multimeter-2626158
3. or in the BIOS to check the +3.3V, +5V, and +12V. - https://www.lifewire.com/power-supply-voltage-tolerances-2624583

2 is the best way, 1 only checks it works and 3 only shows it at idle.
Not many people have 2 though.

No real tests for Motherboard, you test everything else like you have and use a process of elimination. Or you take PC to a store and ask them to check everything and let them tell you. 2nd opinions always helpful.

Could be something else, could be a CPU problem... why I don't like guessing.

Hi, I only assume it crashed while being off because I can't start it. It manifests the same symptoms as crash during being ON. Lights on USB stuff are ON (so they do get power) but I can't start the computer with the power button or any other button.
Only thing that helps is to drain the power from PC. I can see that when the USB lights go off, then power's drained and I can start it without problem.
And yes, there's no recorded error in Windows Event log for when it happens in OFF state.

Will definitely try your suggestions.
Thanks a lot.

 

[Umpire]

Generally speaking in cases like this it is most likely PSU problem. However there is one thing you are missing - Power button. Faulty Power button might cause both problems you described (sudden power off/no power on). So first thing to do is disconnect it from motherboard and use screwdriver method to start PC. If that makes no difference in your PC behavior then next step is try different PSU.

Btw, you mentioned parts are 2 years except case. Another thing that potentially make this problem is short caused by case. So it might be worth to rebuild the system outside of case. Although that's a lot of work so if you can obtain different PSU easily I would rather do PSU swap first and only if that won't help do the rebuild. If nothing above helps then it's time to change motherboard.

Hi,

Shouldn't be a problem to have the caseless setup - just need to tidy up the room.
The power button is an interesting suggestions. I know nothing about that screwdriver method but will do some google-fu to find out. I assume you just use screewdrive to bridge the start pins on mobo and thus connect the circuit as the power button should do, right?

Thanks.

 

[DRagor]

I assume you just use screewdrive to bridge the start pins on mobo and thus connect the circuit as the power button should do, right?

Exactly that. Just make sure to check twice you short the correct pins as any error here can have grave consequences!

 

[Umpire]

Hi,
Many thanks to everyone who provided advice. I tried them all except the pin method with PSU cause I chickened out and assumed that proving PSU runs would not help since I know it runs all the time I want it to – sans the random crashes, of course. Ended with the "naked PC" solution with minimal setup (no unnecessary peripherals etc.). Still no cigar.
So, back to the shop I went and returned the PSU because the warranty still was ON. Describe them the whole thing including the fact that PSU is only ruled out as likely culprit, not 100% certain cause.
Three weeks later I got my money back (was surprised myself) and the same day bough a new one (in the same shop) – GIGABYTE AORUS P750W.
It's been a little over three weeks and no crash. I'm happy and marking as solved.

Happy new year everyone.