PC will only power up...outside of the case?

[mrsnooch]

Okay so not sure if this belongs here or maybe even in the cases thread as that seems to be the common denominator here.

My friend is building a PC and is having some serious issues.

We have checked the 24 pin plug
We have checked the PSU is switched on (!)
We have ensured the plug is in correctly, and also switched on at the wall.
We have ensured the CPU cable is in and firmly so.
The CPU fan is in, and securely tightened.

All this results in a split second 'power on' type scenario, but it quickly turns off after a second. We noticed the CPU fan wasn't even spinning up, so thought it was that - tried in his old PC, worked fine. Vice versa, tried his old CPU fan in new PC, same issue.

Basically we have mixed and matched, old with new, nothing giving us a firm answer.

Until.... we took it all out of the case and powered it from there - and it worked.

Is there anything you guys can think of that would result in this. The only thing I know of is if the case is shorting the motherboard, but we can't see any metal touching, and we have all the gold stand off things in place, so the mobo is raised above the case.

Having a real headache with this.

Or maybe you can think of other possible solutions for when a PC does not turn on?

Thanks very much
Mark

 

[DampDog]

The only thing I know of is if the case is shorting the motherboard, but we can't see any metal touching, and we have all the gold stand off things in place, so the mobo is raised above the case.

Way back we used to build gas analysis machines that were based on a std motherboard and we added custom boards to make it do its' stuff. We had similar problems when we inadvertently mounted the board to the case and didn't notice the edge of the board was touching the chassis. ( it must have had a power rail very near the edge of the board)

Just check the edge of the board is not touching the chassis. Worth a look.

 

[Sir SpankalotUK]

yeah sounds like a short of some kind, check for un-used motherboard mounting posts or that you have the correct size mounting posts installed (e.g. not mounting motherboard directly to the case).

 

[Idleman]

Do you have the motherboard standoffs installed?
These are to prevent your mobo from making contact with the case and causing it to short-circuit.
What case do you have?