How do you fix a case shorting out?

[ed^chigliak]

This is a simple PC upgrade to 9700pro gone wrong with garbled screen during boot and in the bios screen. I also get a similar thing with a GF4 Ti4200 but no such problem with an early radeon card.

Right now the PC is working outside the case isolated on the mainboard box. I cannot see anything obviously wrong with the case so what can I try next.

[Olly1234]

Whats your PSU? Also whats the rest of your spec?

*edit*

Maybe didn't read properly, do you mean it actually works out of the case with the 9700?

[Flibb]

Would normally suggest a mobo mounting post in the wrong hole. Nearly did it to my Asus board

[ed^chigliak]

ASUS A7n8x-x
2.1 XP 166 FSB
512 Corsair value
CD/DVD not connected
Floppy not connected
Running 1xHDD

Tried two different generic 300w PSUs 'macron' brand & 'NX' branded. Also tried feeding the graphics card from my PC running along side.

CMOS has been reset to defaults as per the motherboard manual

YES it does work outside the case with the 9700pro

[Olly1234]

Ahh in that case there is going to be something touching the board or the position of the board once screwed down is making the card in the AGP slot sit at an angle, not quite make contact with the last connectors in it, sure you have all the standoffs in the correct holes?

[ed^chigliak]

Brass standoffs are all in the correct holes washers are topside between screws and the mainboard. The graphics cards is seated correctly.

I've now tried replaced all the standoffs with plastic thumb screws of similar height. The only point of contact with the case is then the backplate on the graphics card. Still got a garbled boot and bios screen. Take it out of the case and back onto the cardboard box and it works fine.

Is it possible there is current flowing through the case somehow? I disconnected the case speaker with no difference.... running out of options now.

[Olly1234]

There shouldn't be anything, but it sounds like something isn't earthing correctly...Can you somehow insulate the point where the card is touching the case, electrical tape of some kind as it has to be this. Also you might take a sheet of plastic and lay that in under the board to test with and without graphics card insulated and see the results..Should imagine it's really really annoying

[Thorsson]

You sure that you don't have a dodgy PSU?

[rajagra]

Brass standoffs are all in the correct holes washers are topside between screws and the mainboard....I've now tried replaced all the standoffs with plastic thumb screws of similar height. The only point of contact with the case is then the backplate on the graphics card. Still got a garbled boot and bios screen. Take it out of the case and back onto the cardboard box and it works fine.

Why were you using washers? I assume you mean insulating ones. The system will work better if you use brass standoffs and just screws to provide better grounding throughout the mobo. If you are insulating the mobo from the case you could well be getting some current flow through the backplate.
Also don't be too quick to say the card is properly seated. Often a case is misaligned enough to stop cards seating properly when you screw them in place - even if they look OK. Try not screwing the card in, as a test.

[shiato storm]

perhaps a wire from backplate where mobo is leading out of the case and physically touching the ground would ensure proper grounding?

[ed^chigliak]

The brass standoffs make contact with the underside of the board and the fibre washers I just use topside and have always built systems like this without experiencing problems. I will certainly try without washers to improve the earthing which is a good suggestion.

Graphics card is not screwed down so is not pulled to one side at an angle as can sometimes happen. Both ends of the card are fully pushed into the slot and the retaining clip on the AGP slot is fuly closed. It's not seated any differently in the case than when it is outside the case. It's has been removed and reseated several times.

Where would you fix an earthing wire to be 100% certain the PC is correctly earthed. How can I measure if the case is earthed correctly?

I'm pretty sure there is nothing wrong with the hardware. I'm now working with a completely new set of components but retained the original case. I am not sure how to solve an earthing problem but next I am planning to try a different case.

[rajagra]

Hmm. Weird.
The PSU is normally screwed to the case, so the case should be grounded by default. The mobo is mainly grounded by the power lead. Using metal standoffs is desirable, but not a specific requirement.
If there is definitely no (unwanted) short between the case and components, that means something more obscure may be happening.
Are you connecting case fans or other power-draining items? 300W doesn't leave much going spare. Not being funny, but I would never use anything less than a 450W PSU for any system.
Might the case wires for switches/LEDs be faulty?
Could the mobo have broken tracks that only cause problems when screwed into the case, causing stress? Is the case actually warped, causing high stress when you screw the mobo in, maybe causing cracked tracks?
Grasping at straws here, sometimes you have to.