Motherboard grounding question

[Sacotool]

I just built a system using an ABit BF6 with an Enlight case. When I first put it together, I had a problem where the system wouldn't boot up unless I removed one of the screws holding the motherboard down. I installed the video and soundcards but I didn't screw them down until today when I was ready to put the cover on. Now after I screwed down the soundcard, the system won't boot up🙁 I assume it's shorting out the motherboard. Any ideas?

 

[DaddyG]

Yep,, you probably have a extra standoff thats shorting a mobo trace to ground on the bottom of your mobo, its very common. Remove mobo and check that standoffs are only at the desired( soldered ring) holes. Look for tell tale scratches on the underside of the mobo where a 'ground' could have occurred.

 

[FlyingPenguin]

Yes, as he mentioned, you almost certainly have an unused metal motherboard standoff that's grounding a pad on the back of the mobo. You're lucky you haven't caused serious damage - you're okay if it reboots with the short removed. There should ONLY be a standoff where there's a cooresponding hole for it in the mobo. Not all the standoff holds on the case get used - mobos use different hole patterns so there will always be some unused standoff holes.

Also use insulating washers on all the screws holding down the mobo (the washer goes on top of the mobo between the screw head and the mobo. ATX mobos should NEVER be grounded to the case via a screw - the single point ground is via the power supply cable. None of the screw holes are grounded BUT sometimes the head of the screw is bigger than the pad around the hole and may touch another pad unless you use a washer.