Computer turns on for a split second, but then...

Hi all, first post here, since this problem has been bothering me for about 6 months now I figured I'd try and fix it this weekend.

nck804a-LFS mobo
AMD Athlon 64 3200+ CPU
Geforce 8500GT GPU
3 x DDR PC3200 RAM (2 x 1GB ; 1 x 256MB)
400W Power Supply
(If you need any other info let me know)

So as the title says, my computer turns on when I power it but only for a split second, the fan spins momentarily. I've searched over google and a lot of people seem to have this problem, but then if I attempt to turn it on again it'll turn on but only the fans will spin. No HDD, no POST no BOOT. nothing. I'm pretty sure there's no other way I can troubleshoot this. It's currently on my MOBO box in my living room, with just the 24 pin ATX connector, 4 pin ATX connector, and the internal speaker plugged in. Absolutely nothing else, no CPU no heatsink, I'm just shorting the power pins. I just want to hear a beep of some sort. I've tried different PSU's. One PSU in the 24 pin connector, the other in the 4 pin connector, I've tried reseating everything, resetting CMOS battery, looking at various guides, even switching CPU fans in case the other one wasn't working thus initiating the automatic protection shutdown, but most of them are problems of it just only turning on for a split second, not the second attempt making the fans spin.
Its a fairly old build, I suspected at first MOBO failure, but there's power going to it. There's a red LED on the MOBO. Dunno if that indicates that there could still be failure. I'm doing my grade 12 co-op class at a local computer repair shop and they have a few extra processors lying around told me I could use them but I figured I would ask you guys first to see if its worth switching the CPU because even with the CPU out and everything else it does the exact same thing as it does with everything connected to it.

Just to recap:
1. I turn it on, fans and HDD spin and power up for about a split second.
2. If I try and power it on again only the fans will start up. And they go strong. They don't stop. The only way I can "power it" (meaning everything turns on for a split second is by switching the I/O switch on the PSU.

If anyone could help me that would be great.

3 answers Last reply
More about computer turns split second then
  1. Unfortunately, you are too bare there. You need a CPU and ram to get a successful POST (single beep). Mount your CPU/HSF, use one ram module only - try to get a beep that way.
    Good Luck
  2. What exactly do you expect to get from the motherboard with just the power supply connected to it ? Have you tried putting a cpu in it to see if you can get a response from it?
  3. I figured if I took everything out and got the exact same situation as when everything is plugged in I could narrow it down that way to know it's definately with the motherboard. As I expected, I seated in the CPU, put some new thermal paste on it, put the fan over it, locked it in and put in a stick of RAM; Same thing happens that happens when it's just the mobo and PSU, first attempt to boot the fans will start momentarily, second attempt they all start up but no POST beeps, no POST.
Ask a new question

Read More

Homebuilt Computer Systems