<div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">My first thought was that I have a bad power supply. But with the<br>blinking light, I thought perhaps something was telling the PSU to
<br>shut down. I checked the CPU heatsink and fan, and everything seems<br>to be working.<br><br>I would greatly appreciate any suggestions. I figure I'll probably<br>cannibalize another machine and start swapping parts out until it
<br>boots...</blockquote><div><br>
<br>
I think you're right to apply the scientific method. Start by unplugging all<br>
devices, leaving only the PS and MB. Power it up, and see if it will stay "on"<br>
for longer than that 15 seconds. If it doesn't, you'll know the problem is the<br>
CPU, memory, PS, or mainboard, so you can start doing part-swaps to find it.<br>
If it does stay on, you can start adding parts one at a time to see which one<br>
breaks it. I suggest this order:<br>
<br>
Video Card<br>
Hard Drives<br>
Other Cards<br>
<br>
Video card is an obvious first choice, because it will make the computer stop<br>
doing POST code beeps and actually do something useful. If you had onboard video,<br>
you'd already be past that part anyway, so ignore that.<br>
<br>
Hard drives are next, because they use a lot of juice and you need them to boot. If the<br>
system is still working fine past the 15 second point, I think you've effectively narrowed<br>
the problem down to one of the add-on cards. Start adding them in one at a time until<br>
you find the culprit.<br>
<br>
If you're hideously unlucky, you'll put everything in and find that it's working fine, only to have<br>
the problem resurface an hour later. I agree that it sounds like a PS or mainboard/CPU problem.<br>
Are you positive that the CPU fan is working? Overheating would be a good reason for a system to<br>
shut itself off 15 seconds after it turns on. That, or a short somewhere.<br>
<br>
- Jeff<br>
</div><br></div>