Video cards are getting fried

I'm working on a PC that appears to be frying PCIex video cards. The first was an Nvidia 7600GS that now has popped capacitors, and now I have a 9500GT that lasted 48hours and now has garbled text/video right from the POST screen. I have done a long-term voltage test on the PSU and it's rock solid, but the -5v line is TOTALLY off. It only reads -0.38v. Could that be what is causing video cards to burn up? The on board video works perfect, and all other aspects of the PC functionality are fine....

 

It is beyond my knowledge of computers, but my primary suspect would be the power supply. Definitely if one of the lines is reading a voltage it is not supposed to.

If you have a cheap video card laying around and another power supply, I would put them both in and see what happens. That way, if it is a motherboard problem, you will find out.

 

It's my understanding that a -5v line is needed only for backwards compatibility, and that your motherboard probably doesn't use that line if it doesn't have an ISA bus. I gather that a -5v line usually isn't provided by today's PSUs. So what make and model of PSU are you using?

You've said that you're seeing only -.38v on the -5v line. Is that with the -5v line connected connected to the motherboard? If so, what reading do you get if that line is not connected to anything? It may be that your PSU does not provide voltage to that line, and what you're seeing is a stray voltage.

However, if the PSU provides -5v on that line but you're seeing only -.38v when it's connected to the motherboard, that suggests to me that there might be a short in the circuitry supplied by the -5v line. But does that have any impact on your video cards? I doubt it, because even in the the old AT standard, the -5v line provided only enough power for signalling -- less than 1A. But I'll leave that question to someone who knows more than me.