New render machine VERY flakey

[tricky]

We have recently built 3 more render machines to add to our farm. They are based around i7 CPUs with 32GB RAM and are running W7. The cases are pretty basic affairs. The PSUs are Corsair Builder series - 400W or thereabouts.

One of these machines is VERY unstable. Very often, a simple 'tap' of the side of the case with your hand will cause it to completely black screen. This happens both in and out of the OS loading. Never had this before. I have checked, double checked and triple checked all connections are solid.

What could cause this instability? Dodgy PSU?

There is very little in the machines - the main board, a CPU (with native cooler), an SSD drive and that;s about it.

[pokoy]

I once heard from a PC supplier that some cases (one in a thousand or so) have tensions that will affect their magnetic field and may cause a system to get unstable or even not load properly. I know it sounds strange but he assured me this happens.
Could also be a faulty or loose part somewhere on the mainboard or somewhere else. I guess you can bring it to a PC house somewhere and get the componenets checked and measured.

[Morne]

Make sure your main board is properly seated and not shorting on the case. If you have any parts from the old days laying around, use the rubber washers between the motherboard and the seating spacers and also on top between the screw and the main board. (screw > washer > mainboard > washer > spacer > chassis)

Could be that the builder tighten the screws too tight and cracked the board

[ior=0]

... I have checked, double checked and triple checked all connections are solid.
What could cause this instability? Dodgy PSU?

Try swapping the PSU with another of the 3 PCs, if the problem moves with the PSU, then that PSU is most likely the cause.
If not, try swapping RAM, although bad RAM is move likely going to give you BSD.
Check your temps?
Swap and re-seat the CPUs, but that can be a bit of an arse to do.
At least you have 3 machines to cross test the different components in.

good luck

[alexyork]

Take it all apart and build it outside the case and test. If you still have issues you know it's something other than your case or the risers for the motherboard shorting it out against the case.