Problem: Case short

Old problem of machine turning on for a second and then turning off is back. Turns out that apparently it is a case short bc when EVGA PSU is outside of the case, it doesn't happen. Already replaced the PSU bc I thought that was it so don't think it's the PSU that is the problem. Can't figure out what is wrong; I seem to seat the PSU right. Problem also occurs when MB but not the PSU is out of the case (I disconnect everything else from the MB). Case is Nanoxia Deep Silence 3 Mid Tower Case. Anyone know what I am missing? Should I buy another case? Which one? Want one as quiet as possible. Thanks.

You could RMA the PSU. EVGA has great customer service. But before you do that, did you make sure the 24-pin and 8 pin connectors are plugged in snugly?

Yes, I've plugged and unplugged the connectors many times and replaced the cables. Already replaced the PSU. I think it has to be the case but I can find no loose screws. Anyway, entire thing is in the case now except for the PSU and it's working. (PSU is on the floor next to the open case.)

So you also have standoffs between the case and the motherboard I assume? If you put the PSU in the case, but not mounted, but elevated with non-conductive material such as a thin book, does it exhibit the same problem?

I do have standoffs. What would the elevation test tell me? It's next to the case on the floor now.

I see, then the short could be from the case.It is just odd that I have never seen anything like that before.

Neither has anyone else, apparently. I suppose I have to replace the case and hope that works. Love your avatar, BTW ha.

Lay the motherboard out on a table and hook everything up and see if it still does it.

While it is on table check case and make sure there aren't any EXTRA standoffs under motherboard. Check the wire going from power switch to motherboard and make sure it isn't nicked and shorting on the case.

It works if everything is out of the case. No extra standoffs. Already bought a stand-alone power switch and tried that, it doesn't help so long as the PSU is still in the case. I hate having to keep buying replacement parts but it seems to be the case and I don't think I can wrap the PSU in insulation.

Only other place I can think of without a picture is maybe around the I/O shield. Maybe there is a piece of metal sticking out near the board.

It didn't work when I took everything except the PSU out of the case. I took the I/O shield off when I did that.

Off the MB, I mean.

The PSU being in or out of the case shouldn't matter in regards to shorts, unless it makes a power cable bend in a certain way that pushes, twists, or lifts the motherboard, and I'd suspect the motherboard because you've replaced the PSU. And because there's no difference when the motherboard is in or out of the case, it's not a short to the case, such as from not enough standoffs, standoffs in the wrong place, or standoffs or their screws shorting to the motherboard. So I think it's one of the power connectors on the motherboard, maybe a pin with cracked solder. Those cracks can be microscopic and visible only under strong light and a magnifier.

Replaced the MB. It didn't work. The only thing I haven't replaced is the case.

NewBuilder said:

Replaced the MB. It didn't work. The only thing I haven't replaced is the case.

Click to expand...

What part of the case can do that when the motherboard is out of the case? The PSU can't be shorted to the case except through its cables, which would have to be defective to let that happen, and the rear opening for the PSU is too big to interfere with anything like the power cord.

Do all the standoffs line up with the holes in the motherboard? Otherwise a standoff can press against copper traces on the motherboard and short them to ground, or worse, a standoff can crush a tiny component soldered to the bottom.

Are the corners of the motherboard supported within 1"? If support is much farther away from a corner, the motherboard and case can sometimes flex enough to make them short together, so when in doubt, install stick-on rubber feet to the case in those locations.

The only other thing I can think of is the CPU heatsink. Heatsinks that use plastic clips sometimes don't seat fully against the CPU because the clips can lock before they're pushed all the way into their holes, and heatsinks that use metal attachment hardware sometimes don't have good electrical insulation. Sometimes the problem doesn't occur outside the case because the motherboard is horizontal then, shifting the heatsink slightly.

My take, as unlikely as it may be, is screwing power supply into case is allowing a short thru "ground" of power supply enclosure or securing power supply is distorting computer case.
Possibly sharp bend of power supply wires when iinstalled in case produces short.

I don't really know, but I've done all the things with the standoffs etc. It continues to work with everything except the PSU inside the case. I am going to put it into a new case and see. I think there is too much slack for bends of the cables at the MB to produce a short based on the PSU's position. Anyway, I've tried replacing the MB, PSU, and cables already and the problem occurs when everything is out of the case except the PSU.

I got so curious about this that I've gone as far as to disassemble my current PC and have a go at it with a continuity meter.

Narrowed it down to the following test.
Are you sure you disconnected everything, including the front audio panel, shutdown/LED/reboot switches? To put it another way, have you tried the following barebones test:

PSU in case, everything else outside. Connect just the motherboard (CPU, RAM, Fan, preferably an integrated GPU or none at all) and nothing more.
I'm talking nothing, not even the PC speaker. Turn the computer on by shorting the appropriate pins on the mobo.
Disconnect mice, keyboards, drives, everything, including the screen.

If this works, put the motherboard part of your system inside the case. Again, just the PSU and the motherboard.

Works? Try connecting everything else one by one. Power, reset switches first, then the GPU, then the front panel USB/audio, finally drives and other stuff.

I did take everything but the PSU out and disconnected everything else from the MB, I mean everything except the CPU and a stand-alone power switch that I bought. Same problem.