Computer only boots when motherboard is outside of case

[hogsdill]

For some reason, I can only get one of my old computers to boot when the motherboard is outside of the case sitting on a piece of plastic. What's the deal? It will boot with video, ram, cpu, and power supply.

After I get it to boot, I set the motherboard back in. Hook up the video, ram, power supply. And it won't boot. No video and no post beeps.

What am I doing wrong? Please help.

 

[Harvey]

Something is shorting between the motherboard and the case when you put it back in. Look for scratches in the insulating solder mask coating on the bottom of the motherboard. If you don't find any, check for other usual suspects including screws or standoffs that are oversized or off their mounting centers and any other metal components touching the case.

Another possibility would be a plug in card, such as your vid card, that is shorting to the rear panel. If that happens, you wouldn't get a short to the case when the assembly is out of the case, but would short out when you put it back. Try reseating the card or temporarily testing it with another card. You'll know as soon as you see the POST screen so you don't have to boot to Windows to know if that's the problem.

Good luck.

 

[Fern]

Prolly an extra brass stand-off mounted on the case.

Ummm.. You are using the brass standoffs to seperate the mobo and the case, right?

Fern

 

[hogsdill]

Yep, using brass standoffs. I think one of these might be the problem. I didn't screw in one of them and that seem to solve the problem. I just kept ruling each one out till I found the culprit.

But I'm still not sure if this is the final solution.

 

[Fern]

Well, sounds good so far :thumbsup:

But later, if after accounting for all the standoffs (usually the problem is that there is an "extra one" under the mobo, and it touches some mobo circuitry and causes a short) it still doesn't work, let us know.

Fern

 

[hogsdill]

I think that I've got it working now. My only problem now is that I get the following error message when I boot.

CMOS GPNV Checksum Bad

I enter setup, change everything like I want, save and exit. And it still give me that error.

 

[stevty2889]

Originally posted by: hogsdill
I think that I've got it working now. My only problem now is that I get the following error message when I boot.

CMOS GPNV Checksum Bad

I enter setup, change everything like I want, save and exit. And it still give me that error.

Check to make sure the clear cmos jumper isn't in the clear position. Also, since you said it was an older computer, it is also possible the cmos battery is dead, keeping it from saving the settings.

 

[hogsdill]

I think it's working now. I updated the BIOS to the latest release and that fixed the CMOS error that I was getting. Thank you all for the help. I still can't figure how I was shorting out the motherboard. But it's working now and hopefully continue to work.