computer complets post and shuts off

[st0rm_r1d3r]

I built a new computer and assembled everything. Everything is compatible with my motherboard and form factor and what not. When i turned it on for the first time, it would turn on for 20 seconds or so and then turn off. I get one short beep which means that it POSTed...am i right?
I did a barebones boot, and ran the motherboard outside of the case, and it still shuts down. I see the Asus logo and try to go into the bios, but it shuts down before it enters the bios. i plugged in the power supply to a known working mother board with a good cpu and ram. it still shut down. So i got another power supply and plugged it into my motherboard. it worked before i mounted the power supply. I let it run for a good 40 seconds or so before i mounted it.
After i mounted it, it gave me the same problems. it turns on for 20 seconds at the most...sometimes 1, sometimes 5....it varies. everything is plugged in tight. the red switch on the ps is set to 115. i've even tried booting with only the power switch plugged into the motherboard. a strange thing is that even though it shuts down, the green light on the motherboard is still on. the first powersupply was 500 watts, and this one is 600 watts. i've been at this for almost 2 weeks :(
I've also tried different ram sticks in different slots. I'm almost at my witts end. Any help would be greatly appreciated. It can't be the motherboard...can it? After all, it worked the powersupply was unmounted.


OCZ 2048MB PC4200 DDR2 533MHz Dual Channel 2x 1 gig sticks)
Asus P5ND2-SLI Socket 775 Motherboard
Intel P4 651 3.4Ghz HT 2M 800FSB Socket 775
XFX GeForce 6800 GS 256MB PCIe
CoolMax EZ Wire 600W

[jlreich]

Hello st0rm_r1d3r and welcome to the PcGuide forums.

Yes 1 single beep means it posted. Any other beeps?

Have you tried the PSU unmounted several times to confirm that it only happens out of the case? That's really odd. :confused:

Did you plug in the square 4pin molex power connector to the motherboard?

CPU fan connected and running?

Touch the heatsink on the CPU after it shuts down, it should be warm but not so hot it burns you finger.

How is the electricity in your house? Try another wall socket on a different circuit.

If you are using a surge protector try plugging it straight into the wall. If you are not then try a surge protector. Is the surge protector old or has it suffered any damage? Too many power spikes? I have seen similar problems with old surge protectors and old UPS's as well.

Others may pop in with more suggestions.

[ski]

Does the system run ok with the PS(either one) and the MB outside the case? If so, then the case may be defective.
If the system still turns off with the above setup and the CPU fan terminal on the MB has 3 pins, then make sure the CPU fan's connector has 3 slots.
If that's ok, then reset CMOS either with a MB jumper, or by removing the CMOS battery for 30 minutes.

[PCMan]

I am no expert in motherboards; however, this sometimes happens when the motherboard senses that the CPU is overheating. Whether or not the CPU is actually overheating is up to the motherboard. Be sure that you have a heatsink with thermal paste and a fan on top the CPU.

It could also be that the thermal sensor on the board is off, and therefore it senses the CPU at too high of a temperature and shuts off.

[PrntRhd]

PC Man:
Be sure that you have a heatsink with thermal paste and a fan on top the CPU
st0rm_r1d3r,
If you installed the heatsink with a thermal pad, you must remove the plastic sheet covering the pad. It is common to miss this when setting up that first PC.

[st0rm_r1d3r]

thank you all for the advice. the heatsink wasn't making proper contact with the cpu, so the motherboard was shutting it off because the cpu was over heating. The cpu got as high as 72 degrees celsius. But i had to press down pretty hard to get it to work. I was scared that I was going to break my mother board. I think one of the plastic install pins is kinda messed up so i'm going to have to get another heatsink and fan. It's probably going to act up everytime I move the computer around. The socket 775 heatsinks are weird to install. I've never seen anything like that before.
It was funny though, when I turned it on without any ram, the rytem of beeps got slower and slower like the power was being chocked out. All this time it was such a simple solution. lol. Once again, thank you for your advice.

[azzey]

Remember that if you remove the heatsink, you must clean the old thermal pad / grease off and reapply.