motherboards not starting up??

[hfxrzw]

I have posted earlier, but could not find a solution. After having left it for some time I'm back for more pain I guess.

I had a problem with the original computer with a broken mobo. Initially I thought it was the powersource, so replaced that. No go. I then started switching parts with another computer without success and ended up buying a second hand mobo. This didn't work as well, so rather p****d off! Bought a new mobo and had a similar effect. Completedly lost now.
I'm at a stage I don't know where to look any more. I have two motherboards with two power sources with two different fans with two different sets of memory with two processors and both react the same; nothing goes when switching on. Shorting the green wire on the plug to ground gets all the fans running and all connectors measure as they should (0/5/12V), but the computers don't start up and as soon as I remove the short they are dead again. Any tips on what I can do? There are no beeps from the boards with a speaker connected.

Thanks, Rene

 

[johnb35]

Did you use the brass standoffs between the case and motherboard? Have you tried assembling the motherboard outside of the case to determine if you were shorting out against the case? This is what the standoffs prevent is shorting out against the case. Are you using onboard video or a dedicated card? If dedicated card, is it a high end card that needs its own power connections from the power supply?

 

[hfxrzw]

Hi John, thanks for helping out.

Basically yes to all your questions. I used the stand-offs and the video card has its separate feed. I tried it with the card fitted (with the power feed) and without the card for both set-ups without success.

Cheers, Rene