Computer Shutting Down Randomly

[festus]

I started having a strange issue with my computer a few days ago. It runs fine and then just shuts down by itself. This can happen while gaming, browsing or even when the computer is just sitting idle.

When it shuts down, I can start it back up right away without any issues other than the warning that it wasn't shut down properly.

Bit of info on the computer, it's a bit older:
CPU: Phenom II X4 955 Black
Video: Radeon R9 280x
MB: Gigabyte MA79FXT-UD5P
Ram: 2x4GB Mushkin PC3-10666
HD : Samsung 840 EVO 250GB
2 x WD Caviar Black 640 GB
Power: Corsair CX750 (added about a year ago as previous PS had died)
Sound: Soundblaster XFI Elite Pro (I've removed this and the issue persists)

This machine has been problem free up until a few days ago when this started. The only odd thing is that it stopped going to sleep about 3 weeks ago, it was configured to shut the hard drives off after an our of idling.

I don't believe this is a power supply issue as all of the lights on the MD, video card, soundcard all stay on when it shuts off. Power doesn't seem to be lost, it just shuts off.

I used OpenHardwareMonitor to check for heat and the CPU doesn't seem to go about 55C, I think the video card got up to about 69C.

I had tried running check disk on my main harddrive and all I got was a black screen and couldn't get into windows at all. I was able to run SeaTools for dos (short and long tests) and everything passed. I couldn't repair windows, so I figured I'd install windows 10. It packaged everything up into a windows.old folder, so I was still able to get to everything I previously had in windows 7. The machine shut it self off again yesterday though.

Any thoughts?

 

[Ketchup]

Definitely a power issue. A hard driver issue wold either freeze the computer or write a dump file. And it isn't a Shut Down command running, so that rules out pretty much all software.

I don't know that this narrows it down very much though. If you have a power supply lying around or in another computer, you can try that. There could be a short somewhere in the case. You may want to take out the power button and make sure it is activating properly.

If you have a battery backup, you may want to plug the computer directly into the wall and see if the issue goes away.

 

[Raizinman]

The hardest part in solving a problem is the denial of what part(s) you believe to be bad.

Change out the power supply.

 

[cholley]

+1 for PS, another thing to do is inspect the mainboard for swollen/leaky caps, especially around the voltage regulator.

look also at cooling/airflow but typically temps would lead to bluescreens

 

[festus]

Thanks guys. I don't have a spare power supply around the house, but I believe the PS is still under warranty, so I can give them a call and see if they'll swap it for a new one.

I'll have a close look at the board for any caps that look like they may be going before I head to the store.

I have the side of the case off and have been running some intensive programs for the past 2 hours and the temperatures seem pretty good
These are the Max numbers:
MB
Temp1 : 35C
Temp2 : 55C
Temp3 : 48C

CPU : 53.5C
GPU : 65C

Oddly enough, it hasn't shut itself down yet today.

 

[WebDesigners]

I had similar issue with PC shutting down. Then i realized that two of bolts which holds CPU's cooler got unlatched, so when CPU gets over heated it shuts down computer and I can't turn it on until its cool down.