what can cause pc to power up for a second, then power itself off?

[ny_driver]

it was doing it yesterday when I first got it, but then that ceased to happen. I finally got it programmed with OS and stuff, then today I had a bad flash, took it all apart, then decided to try to recover the bios before getting a new chip, put it back together, and now it's doing this again. It's only powering up by the switch on the PSU also, which it was also doing yesterday at first.

Another day, another problem.........

 

[Neuromancer]

Sounds like the front panel connectors may be installed wrong or you have a bad case switch.
Try removing the FP connectors on the motherboard and just jumping the two pins for "power switch" on the motherboard for a second with a flat tip screwdriver.

IF you hold the screwdriver there for more than 4 seconds it should turn back off, and if you use a normal jumper it will turn on and off repeatedly

(A power switch is a momentary switch it only creates a closed circuit for as long as you hold the button in)

 

[Mr.Guvernment]

could be your PSU not powerful enough?

was this system working fine before the bad bios flash?

 

[dorkbert]

Perhaps you have a short in the system somewhere? Remove all the bits you don't need to boot the system (yes, that includes both optical and hard drives) Leave just the video card (if you don't have IGP,) one stick of memory and the cpu. If you can't get that to booth either, try using non-conductive washer on the screws securing the motherboard to the case. If that works, start adding back components one at a time.

 

[ny_driver]

I swapped out PSU's and it works. Then I took the "faulty" PSU and hooked it to the other system I'm building for my mom and it seems to work fine.

 

[dorkbert]

Sounds like Mr.Guvernment is right then; the system is pulling too much current and that particular power supply shut itself off to protect itself.

 

[Mr.Guvernment]

Sounds like it, what kind of PSU was it? cheaper no name brand or a brand name one?

i know no name brands work, but usually as soon as you put any real load on them, that is when things go bad!

 

[ny_driver]

It's an antec 420w switching power supply. I didn't really have any load on it, just mobo, cd drive, HD, and floppy, the vid card was powered by the agp slot.
Right now it has all those things on it, but it's on a different mobo and it's been working flawlessly for several days. And I'm using the mobo it was hooked to in my system and it works fine. I dunno what it was, but it is kinda strange.