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Psu or Mobo failure?

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Warren G

Member
Joined
Jun 14, 2002
Location
California
Recently, my computer has been shutting down at random times. Like a complete Windows shutdown where it goes through the logging off / shutdown process. Also have an issue where the computer would turn on automatically by itself. I pulled the mobo header (thinking it was an issue with the case power button) but it still turns on by itself. Could this be either a PSU issue or mobo issue? Before that, it has been rock stable for years. Don't really have another mobo or psu to test, so I might have to make a purchase to test so I'd like to make sure I'm buying the right part lol.
 
Are you turning the computer off completely and not just putting in sleep or hibernation when this happens? Some updates can wake up a computer that is in sleep mode.

You should also check your BIOS to see if wkae up via LAN is enabled and turn it off. I would go in to the event viewer and see whats going on during the time it shuts down or turns on. See if its time correlated or if it coincides with an application.

Some shut downs are a result of thermal throttling.

Typically when you have a computer shut off due to a failed or failing power supply it just goes instantly. There wouldn't be a shut down process. There could be a short on the power switch header pins or a faulty power switch on the case too...

Could be a lot of things and you are probably going to have to start eliminating suspects one by one. To test the idea that the problem is coming from a short or grounding issue related to the power switch you could pull everything out of the case and rebuild the computer ontop of a cardboard box. This would also be a good time to test with a different power supply.
 
With the power switch disconnected from the motherboard, what happens if you touch the power switch pins (on the motherboard) with your finger while the machine is running? It could be a bad pullup resistor, as rare as it might seem.
 
I'll take the mobo out of the case this weekend and test it out. As for touching the power switch pins on the motherboard while the machine is on, nothing happens.
 
Warren, does the PC hard-reboot, i.e a complete power cycle? It could be your memory as well. How frequent are these events? Every hour, every half hour?
 
The shutdown is random, not as frequent and not a hard reboot. I could just be browsing the web, playing a game, or leaving it idle then all programs just closes out and it shuts down (full shutdown process, not instant off). Happens like once every other day. The random turning on happens all the time. Computer will not stay off. I have to use the psu power switch to keep it from turning on. It will stay off for like a couple minutes then turns on by itself. I googled the issue, seems like it may be related to psu :\ I'll run a memtest tonight and see if its related to memory.
 
I would disconnect everything but the keyboard and mouse. Also check and see if there were any recent updates reducc900 pointed out a recent Microsoft update that has caused issue not the same as yours but..... Also do some scans, I had a backdoor get into one of my PCs years ago that caused similar symptoms as you describe.
 
Warren, if it is a controlled shutdown, then it is most likely OS related. You could make a Linux (say Ubuntu) live USB, boot from it, browse the web etc and see if your system shuts down. If it does not, then the problem is with Windows. If it does shut down, note the error message and report back here. Let us see if it is a hardware or a software issue before disconnecting devices.
 
Figured out the issue. After trying a different PSU, problem was still there so I figured it had to be mobo. While taking the mobo out of the case, a screw fell out. Low and behold, the screw was shorting my mother board :facepalm: thanks everyone for the suggestions. I was really close to buying new hardware (tempted to upgrade).
 
Figured out the issue. After trying a different PSU, problem was still there so I figured it had to be mobo. While taking the mobo out of the case, a screw fell out. Low and behold, the screw was shorting my mother board :facepalm: thanks everyone for the suggestions. I was really close to buying new hardware (tempted to upgrade).

Called that one! Glad you figured it out
 
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