Computer Shuts down unexpectedly, then won't restart
Posted on 2006-11-29
Symptoms: The computer shuts down unexpectedly after 15-30 min. of operation, then won't restart until some time has passed - it had shut down on its own, was left until the next day when it booted fine and ran a bit again, but then, once again, it shut down unexpectedly and would not start (the Power Supply fan turns on as well as the CPU fan).
1) I booted into the BIOS and monitored the CPU temp. It’s a P4 1.8 and runs at an idle temp of 42Cº.
2) I booted into Safe Mode and let it run … until it shut down. Then I proceeded to disconnect each internal component, one at a time, while trying to restart after their removal: 1st I disconnected the DVD-ROM, and then I tried to restart, then the RW, then the HD, Floppy, PCI cards, graphic card, RAM, all without success (excepting the fact that the Power Supply fan and the CPU fan run as I mentioned above).
4) I connected another power supply, and the computer started right up. Problem solved!!! Not so fast. Out of curiosity I tried the original power supply again, and it started it right up too! So, that was a little weird, but probably still a problem with the old Power Supply I thought.
5) I did some more extensive testing with the replacement Power Supply (the new one), and couldn't replicate the original problem; things were looking good.
6) I changed the physical location in order to do longer term testing, and upon nothing more than physically connecting the monitor, keyboard, mouse, and power cord, the computer once again WOULD NOT START UP. Now that was really weird, so weird that I checked to see if the power cord was unplugged. It wasn't.
7) I took the new power supply out and tried it in another computer. It wouldn’t start that computer either. I checked the new PS with a tester, and it continues to test good, but now it doesn't seem to have the Amps to get any computer going.
8) Back to the computer itself, now with no PS since I had taken the new one out to test it on that other machine, and, again, out of curiosity, I tried the ***OLD*** PS, and the computer booted fine. Incredible. A little dizzying. So, why not give it a try with the new PS that wouldn't boot either machine? Would you believe it? Don’t - things are weird here, but we're not talking about miracles. The new PS is fried.
It could be coincidence that the new power supply just happened to fail in this circumstance, but I'm doing some reading and searching before I put another new PS on the front line. I haven't dismounted the CPU yet, but it looks fine. It runs warm but not hot. The next step is to test the CPU, right? Nevertheless, I don't think it's the CPU. This looks more like a short problem of some sort? A short due to the case and/or motherboard?
The truth of the matter is that I’m not really sure if I have really narrowed things down to the CPU, motherboard, or the case. I'm not sure that I have really eliminated the other components because everything was reconnected when it failed again, mortally wounding the new PS. It could be any one of the components that fritzes out the PS (in one case simply disabling it for a spell, and in the other complete killing it). I've seen similar things before, but normally everything is reset either disconnecting the external and/or internal power supplies. But this one has me stumped.
Any insight? Advice? Similar experiences? Am I looking at weeks of testing? With the possibility of more PS casualties?