Help, I can't use my computer because it shuts stuff off, yet doesn't turn off completely.

Wheel in the Sky

Distinguished
Aug 17, 2013
94
5
18,545
I built a computer almost 3 years ago, and I am having a problem now.

First the monitor, keyboard, and mouse shut off, but the computer stayed on and the lightning bolt LED lit up on the case. The only way to shut if off was to hold down the power button. Then I turned it back on. After a few minutes it happened again. I opened the case and cleaned lots of dust out, and then it ran fine for a week.

But today the same thing happened again, so I opened it up and cleaned much more thoroughly, especially the CPU heatsink, which was very dusty upon close inspection.
Well apparently that made it worse because now when I turn it on, after a few seconds it seems to shut off and turn right back on with the lightning bolt LED on the case lit up, and my monitor, keyboard, and mouse stay shut off. My front case fan, bottom case fan, and CPU fan run in this state, but the rear (exhaust) case fan that is behind the CPU is now off. I think this is exactly what was happening a week ago, I just didn't have the case open to watch.

Was dust the problem? Did that have nothing to do with it and this is a component failing?
 
Solution
Sounds like overheating or failing hardware

I'd say you check the thermal paste on your CPU. It's been 3 years so it could be a good idea to apply a fresh coat. Tell me how it goes

Hope your problem gets rectified soon

heavensdown

Distinguished
Aug 15, 2014
72
0
18,660
Sounds like overheating or failing hardware

I'd say you check the thermal paste on your CPU. It's been 3 years so it could be a good idea to apply a fresh coat. Tell me how it goes

Hope your problem gets rectified soon
 
Solution

Wheel in the Sky

Distinguished
Aug 17, 2013
94
5
18,545


Thanks for the response. I replaced the thermal paste on the CPU. No change, unfortunately :(
 

Wheel in the Sky

Distinguished
Aug 17, 2013
94
5
18,545
I tried turning it on after it sat overnight, and it let me log in and stay on for a few minutes before shutting off just like before. I had time to download Core Temp, and it looks like the problem is not overheating (http://www.imagebam.com/image/f62b61487977885).

Another symptom I noticed was tiny, flashing green specs peppered across the screen. I took a screenshot of those too, but they only show up on the problem PC. That can't be a problem with the monitor because I'm using the same monitor right now. And yesterday I tested the HDMI cable, and it's fine, and I tried using a known good HDMI cable, which didn't fix any problems when used.

So any idea what is wrong???
 

Wheel in the Sky

Distinguished
Aug 17, 2013
94
5
18,545
I put in a PSU that I know is working, and now the bad PC is working fine :p It hasn't shut off for 10 minutes now, so a failing Power Supply Unit was the problem. Thank you all 1 person who weighed in, I love you all!