Question Computer powers off instantly, mainboard problems?

Jamlev

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Mar 19, 2012
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My PC will randomly shut down in an instant with no warnings whatsoever. Just an instant power off, sometimes it'll stay on for hours, sometimes ten minutes.

It has also done it when plugging in any USB device into any of the slots which leads me to believe it is a mainboard issue. To get it back on again, the power cable needs removing until the mobo lights have gone out.

There is nothing in the Windows system logs to indicate a software issue and no blue screens.

Mainboard is an ASUS B450 TUF Gaming and it has been replaced before under warranty for a related power issue (it wouldn't come on at that time).

I've tried booting with all USB devices unplugged and it still does it.

Anything else I can check before ordering a new mobo (definitely not an ASUS again)?
 

Jamlev

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If it was CPU overheating the shutdowns wouldn't be so random would they? Sometimes it stays on all day with no issues.

PSU a possibility but I don't have another to test it and with such a random problem there is no point taking it to a store to test as it'll work fine there.
 
If it was CPU overheating the shutdowns wouldn't be so random would they?
...
If it was CPU overheating it would be directly related to what processes are running. You'd be doing something that's hitting the CPU pretty hard. Either that, or the heatsink is loose which is something pretty easy to check.

But a really good possibility is the PSU. What brand/model and how old is it? If old enough then replacing on principle alone might be a good idea.
 
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Aug 22, 2020
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If it was CPU overheating the shutdowns wouldn't be so random would they? Sometimes it stays on all day with no issues.

PSU a possibility but I don't have another to test it and with such a random problem there is no point taking it to a store to test as it'll work fine there.
Thats true. CPU tempuratures can very depending on what tasks/processes you are doing. And how many processes are already going on. The motherboard is programmed to automatically drop all cpu power when it overheats and basicly shut the whole thing down. Gpu could also be a thing. A loose gpu can cause issues too.
 
Thats true. CPU tempuratures can very depending on what tasks/processes you are doing. And how many processes are already going on. The motherboard is programmed to automatically drop all cpu power when it overheats and basicly shut the whole thing down. Gpu could also be a thing. A loose gpu can cause issues too.
WRONG! The motherboard DOES NOT monitor and control the CPU that way. The CPU itself is monitoring its temps and throttles accordingly.
 
Aug 22, 2020
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WRONG! The motherboard DOES NOT monitor and control the CPU that way. The CPU itself is monitoring its temps and throttles accordingly.
True. But i was talking about how most motherboards can shut the system down when the cpu gets over the limit. And i never said anything about the motherboard itself throttling the cpu.
 

Jamlev

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Ok, I've done some more testing and eliminated the CPU. Took the entire thing apart and rebuilt it, reapplied thermal grease, and reseated the processor (Ryzen 5). It'll power up and sit idly with the bios screen up for hours on end, CPU temp is in the low 40s.

As soon as anything is plugged into any of the USB slots it shuts off instantly.

PSU is a Coolermaster 750 Gold rated so need to test that in a different machine to see if it is that or the mainboard (which is what I suspect it is).
 
Ok, I've done some more testing and eliminated the CPU. Took the entire thing apart and rebuilt it, reapplied thermal grease, and reseated the processor (Ryzen 5). It'll power up and sit idly with the bios screen up for hours on end, CPU temp is in the low 40s.

As soon as anything is plugged into any of the USB slots it shuts off instantly.

PSU is a Coolermaster 750 Gold rated so need to test that in a different machine to see if it is that or the mainboard (which is what I suspect it is).
Remove motherboard from case and test again. Make sure there's not a short against the case.
 
Sep 26, 2020
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i have this problem too. also my mb is asus but it wont stay in windows logo .
and also i can see this problem when i click on "bios update" after click it turns off and on instead of restart.
may you pleas check it for me on your bios part please????
 

Jamlev

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Ok, tried everything outside the case and it still does it ... so not the case but thanks for the suggestion.

Its either PSU or mobo.
 

Jamlev

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Managed to test an old 650w PSU and it no longer shuts off when a USB device is plugged in so it was the power supply after all.

Just shows that those Gold rated ones are no better than the regular ones despite being twice the price.
 
Aug 22, 2020
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Managed to test an old 650w PSU and it no longer shuts off when a USB device is plugged in so it was the power supply after all.

Just shows that those Gold rated ones are no better than the regular ones despite being twice the price.
Wait it was a gold rated? Oh damn dude you should really contact whoever made the PSU and tell them what happened. Maybe they can either refund your cash or try to get a replacement. Because for a gold power supply? Oh heck no thats just unacceptable for a power supply that costs that much money and cant handle a simple USB drive.
 

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