Monday, December 24, 2007

Computer switching itself off.

A customer has an XP computer that just switches itself off after running for a little while. My first thought was a dusty CPU cooler. The CPU protects itself by shutting the system down.

I went to the site and the computer would not even switch on. I took the covers off the tower and disconnected the microswitch. I shorted the pins with a screwdriver to try and start the computer but no-go. I used a PSU tester and all the lights came on (except -5V) so I knew it was supplying power. I thought the -5V light on my tester may have burnt out from banging around in my tool bag.

I was thinking motherboard at this stage, the computer was an older Pentium 4 machine and a motherboard replacement would be costly and the customer would probably opt for a new machine. I packed up the computer and took it back to my workshop. I tried to start the computer by shorting the pins and this time it worked. I reconnected the microswitch and it wouldn't work so the switch was broken (which I have also seen switch a computer off randomly). I installed a new switch cycled the computer a few times. I left the computer on and went off to write out the invoice thinking another case solved. I turned around and the computer had turned itself off again. It wouldn't switch itself back on either until sometime later. I tried a new powersupply and this seemed to fix it. I cycled the machine 4 or 5 times and left it on for a few hours and it performed okay and marked this as solved.
Update: I also discuss this subject on my website "computer shuts down"
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