Weirdest, strangest goddamn motherboard problem I've ever come across (related to A7V333)

[GusS]

I got an A7V333 board today.

As soon as I opened the box, I checked out the jumpers and I tried testing it out of the case only using the CPU, Fan, power supply, video card and a stick of memory. No problem, system posted.

I then connected all my other devices (still on my desk) and tried booting again. Again, everything's great.

So I then mount it inside my case, screw it to the screw posts, hook everything back up, and start the system: No post, the speakers inform me "system failed cpu test".
I check all the connections again, same thing. I remove everything but the CPU, mem and video card, still "system failed cpu test". Additionally I sense a burnt smell coming from around the fan area.
So I'm thinking I fried it or the CPU. I test the cpu on another machine and no problems. So I unscrew the motherboard from the case in order to bring it back to the store.
I then decide to test it one more time, out of the case, and to my surprise the thing posted.
I then put it back in the case without screwing it in - still worked.
I then placed it exactly over the screw posts and used only two screws - not tightened (and I also screwed in the PCI/AGP cards) - "system failed cpu test", and the burnt smell came back.
I then removed all screws and displaced it slightly, and here I am writing to you.

What's happening here?

 

[mechBgon]

If you mean that it is now running properly, I'd guess something on the underside of the motherboard was being grounded by the case. Maybe you should pull the board out and check the underside for burns that would reveal what's getting grounded out. Could there be extra studs in your case that don't correspond to the screw holes?

 

[jonnyGURU]

To help dissipate heat from the 5V circuits running through the motherboard, Asus uses the bottom most layer of the board for all of the 5V circuits. Good idea on paper, but this makes them VERY susceptible to grounding out.

Double check you stand off and when you reinstall the motherboard, use the insulating paper washers on BOTH SIDES of the board where the board mounts to the stand off.

 

[GusS]

Makes sense.

However I don't think I've received more than 2 paper washers. Guess I'll be paying a visit to the hardware store.

Thanks

 

[NicColt]

there's called spacers.. you need spacers in place before screwing in your board if not your board isn't grounded and won't post.