[Troubleshoot] PC Powers on for < 3 sec., then retries... over and over and over

N

nonis

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Jun 22, 2009
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Hi guys. Fun times here: I'm a software developer so of course I'm the family "Help, my computer doesn't work" guy. My little sister's home brew PC stopped working and I'm trying to help her...

The PC powers on for a few seconds, then turns off. Nothing displays, it definitely doesn't post... Pretty much as soon as the fan on the CPU stops spinning, the lights turn on again and everything powers on again. The cycle repeats continuously until I power off the PSU. When it powers on, it seems like everything is running: The fans all spin and all the lights turn on. It just never gets anywhere and starts over. It doesn't beep or anything, just repeatedly tries to power on and then dies.

I've tested all plugged in cables of the power supply with a voltage tester and they check out. I tried popping out the memory and testing it with each stick individually (even though there's no beeping or anything). I also unplugged everything, removed the CMOS battery, and reset it a few minutes later. All with no luck.

The only thing that has given me any change was unplugging the hard drive. If I remove the power cable from the hard drive, everything boots without restarting and I get to a screen saying there is no bootable disk.

Does this sound like a common problem at all? Should I grab a new hard drive and replace it? Maybe just try swapping out the SATA cable? Or does this sound like it could be a problem with the PSU (even though the voltage on the power cable going to he drive is correct)?

Thanks for any insight!
 
Do you have another disk to boot from and/or a boot CD that you can boot from while the hard drive is unplugged?
 
I don't have a drive lying around, but I have a flash drive with linux on it, and I could throw something on a CD to boot from.

What were you thinking I should check out, though? Or just see if it will run off another medium?
 
Well if you can boot off a CD and/or thumb drive with the hard drive not plugged in, that sort of narrows it down to a faulty hard drive.
 
I'll share a fast story that might shed some light on this. Built a new system with a few old parts, and for the life of me and everything I tried, it simply wouldn't boot. I tried everything till I decided I was going to go through piece by piece and find out what it was. Long story short, it was a 3.5" floppy drive, BUT, when it wasn't in the case, it booted fine. Turns out, if I had ALL 4 screws in, it wouldn't boot, however, if I left out the front left screw, it booted just fine. I don't know if it was dropped at some point, or what ever might of happened, but that screw shorted something out. Same size as the others, nothing out of the ordinary. I'm willing to wager either the drive is faulty or has a short, or even the molex going to that drive might have a short.
 
My first thought after unplugging the HDD an having it start was a short somehow with the disk. I'll try setting it on an anti static sheet or something and booting it without the screws in. I don't think it's the molex because it checks out when I plug it into a PSU tester, but maybe it shorts on the connection to the hard drive.

Thanks for the tips. I'll report back with anything I figure out.
 
If your molex checks out fine I'd put my money on the drive. I hope you figure it out, situations like this make me want to rip my hair out :)
 
Yes... Same here.

I tried removing the drive from the box in case it was shorting with no luck. I guess I'll have to replace the drive itself. Unfortunate, since she apparently hasn't backed anything up in a very long time.

Thanks, everyone!
 
Bleh... So I replaced the hard drive but it has the same problem. Maybe I was just too hasty in my troubleshooting before but now it seems that even with the drive totally disconnected the PC powers up, shuts off, and cycles over and over.

However, I had it running constantly for >10 minutes by removing the video card. I have no idea though if the power supply is dying and can't power the video card or if the video card is dying. But, when the card is connected it displays video for the short time that the PC powers on... So should I go with trying to replace the PSU or the card? Is there any way I can test if maybe I'm drawing too much power from it or something? She was using this PC in the same exact configuration for at least a year so I doubt it's not powerful enough but maybe it's dying...
 
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