Computer fails to POST sometimes

[Packin]

About a month ago, my 1.5 year old build began to have problems POSTing.

The hardware:

Gigabyte P35-DS3L
C2D E4400
Arctic Cooling Freezer 7 Pro
Crucial Ballistix DDR2 800 2GB (2x1GB) (rated for 2.2V, but running at 1.8/2.2 does not seem to make a difference)
ATI X1950 PRO
WD 250GB SATA HDD
Random firewire PCI card

When I turn it on, all fans turn on, the hard drive spins up, CD-ROM drive spins up, but the monitor remains dark and my USB KB/Mouse do not seem to have any power.

I managed to run Memtest86 with 1 stick of RAM and no errors were found, yet the system still failed to boot all of the time even with just that 1 good stick of RAM. I have been able to boot with both sticks of RAM as well, but it takes a lot more power cycling.

To me it sounds like my motherboard may need to be replaced, but I can't tell for sure. Does anyone have any ideas of what is wrong?

Thanks!

 

[techmanc]

I would check all your hardware power and cable connections ide/sata/power/mother and your installed card for poor connection. reseat the cards and unplug/plug your connectors. the mouse and keyboard plugged directly into the computer or a hub?

 

[Lanyap]

Either motherboard or PSU. What model PSU so you have?

 

[Packin]

Originally posted by: techmanc
I would check all your hardware power and cable connections ide/sata/power/mother and your installed card for poor connection. reseat the cards and unplug/plug your connectors. the mouse and keyboard plugged directly into the computer or a hub?

I'll reseat everything when I get a chance. My keyboard and mouse are plugged directly into the computer. I mentioned that they don't turn on because it doesn't look like any power is going through any of the USB ports. I have a wireless USB device that should be lighting up as well, but it doesn't (I've disconnected it temporarily until I can fix this problem).

Originally posted by: Lanyap
Either motherboard or PSU. What model PSU so you have?

I have a Corsair 520HX so I'm still leaning towards it being the motherboard.

 

[techmanc]

I agree that motherboard/psu could be faulty but its easy enough to check the connections first as that maybe the problem.

 

[Lanyap]

After checking the connections you may want to swap out the PSU from another working PC.

I would also suspect the RAM even though you have run memtest already. Those Ballistix 2.2V sticks have a high failure rate.

 

[Juddog]

As mentioned above it could be the motherboard as well. I had this happen to me for a while and then one day instead of booting sometimes and not booting other times, it simply wouldn't boot at all - lights came on, fan, but no video, and keyboard didn't respond. I reset BIOS via jumper with power drained (unplug power and hold in power button 30 seconds) and still nothing. I replaced the motherboard, and it's been working ever since no problem, so in my case it was definitely the motherboard.

 

[deathwalker]

I am firmly in the Motherboard/Power Supply side of the post here. But I am leaning a bit more toward Power....perhaps a marginal Rail. but a Motherboard issue is certainly within reason also. I would buy a new(quality) power supply, if it doesn't fix your problem then you have a spare power supply, which is never a bad idea.