Short in computer case

Factual Questions
1

I’m pretty sure I’ve got a short in my case (the computer runs fine “breadboarded,” but in the case, reboots every 7-8 seconds, no video, doesn’t appear to complete POST).

I’ve tried two different MBDs and power supplies with no change.

I’ve also disconnected everything from the MBD - same thing: reboots while in the case, fine outside of the case.

I’m thinking I should replace the stand-offs, but they are, I believe 41mm and MicroCenter (local PC supply store) didn’t have any.

Any sharp Dopers out there have any ideas on what I might be able to do to fix this? I’m thinking that if I could find some nylon/plastic standoffs, that would probably do it, but I’m not having any luck finding them online.

2

Your case stand-offs are over 1.5" high??? What?

Normal stand-offs should not cause an issue as their contacts on the motherboard would be routed to ground, if they were routed to anything. Certainly a short could cause your symptoms. Have you checked that nothing on the motherboard is touching the back panel of your case?

3

Yeah, the stand-offs are pretty huge - this is an old rack-mounted server case.

I’ll double-check that nothing is touching the back of the case.

(and thanks for the help!)

4

Can you place something non-conductive between the mother board and the case, as a test?

If the case is conductive, then JKilez’s thought seems likely - you have something shorting to it, which is in turn shorting to ground.

5

as board styles got smaller traces get closer to holes and edges. i did have an older case with metal stand-offs, a smaller board needed nylon to keep from shorting.

6

Has this board ever run properly in the case?

Standoffs don’t normally go bad, but if it’s a new build, or at least the first time that board has been mated to that case, I’ve seen plenty of cases that had several “extra” spots to put standoffs in the name of “universal” fit, so there may be one in a bad place.

The next troubleshooting step might be to put electrical tape over the tops of the standoffs and put the board back in to see if it can POST. If it boots, then it’s almost certainly a standoff problem, but if not, time to look further for anything that may be touching the board, pinnching cables, etc.

7

yeah the MB’s are expecting plastic stand offs. … They have the traces right up under the circled area meant to warn them not to put traces there

8

It is the first time this board has been in this case.

I think the electrical tape idea is going to be implemented when I get home tonight!

(if it makes a difference, most of the parts in this are last-gen or older: them MBD is a Supermicro X7SBE (because I had known-good Core2 Quad CPU and a new, if old, 14-port SATA RAID controller)).

9

Especially with a non-standard case, I’d make sure the standoffs are in the expected locations. My brother (not the most technically inclined) sought my help with a similar issue with his first PC - turns out he’d been overzealous with the standoffs and filled in every hole the case had, thus bending and grounding out the board. :smack: