Grounding a Rack-Mounted Motherboard?

MadCow-ard asks: "Here is one for the Electrical Engineers among us: I have a rack-mount case that I had installed an Intel D845GBV and P4. I had to switch them out with an Asus A7V333 because of incompatibility with my other hardware (which is a long story for another day), but they were functioning fine otherwise. In doing so we found that the new motherboard would not work in the system. We checked everything: multiple motherboards, video, RAM, power supply, cables, you name it. We were getting AOK POST sometimes, others not. It would randomly boot and other times it had no video, or a partial boot. After going nuts (in the field with a couple of clients) we switched out the risers the motherboard sits on. Voila. The risers appear to have grounded the system board. Not the Intel, just the Asus. I spoke with another tech associate who claims to have seen the same issue recently. Now grounding I understand, but it seems that it wasn't the risers specifically. It was their height. We tested two, the bad ones were 2mm smaller. It could be the alloy, but I thought that motherboards would shield the screw points from grounding. It appears to have been a field that built between the case and motherboard due to the smaller risers. It wasn't actual motherboard contact with the case, I checked. Does this make sense? Has anyone else seen this? Is it some sort of capacitance with the case that is generated specifically from the board design and layout?"

Comments

It's a "known" grounding issue!

[Rsimark]

I'm on my third MB of the same make and model =(

The #1 memory slot was bad in the first one (still under 30 day warranty). The first thing the tech looked for was a grounding problem with how the MB was mounted. Seems ASUS has advised the authorized techs about a mounting problem that can lead to a ground shorting things out. Can't recall which mount it was, but think it was one of the ones near the back of the PC, near the external connectors between the PCI slots and the CPU socket.

New MB #2 fixed the bad slot, until it mysteriously died 30 days later.

Understandably, I'm not happy with Asus MB quality thus far and still have new MB #3 in it's RMA box while that cheap Soyo keeps chugging away. At this point "quality" has lost out to operability.