Testing PSU and -5v

[gracious]

I read the post from lowongas regarding the lack of the -5v dc on the dynex psu and it being a non issue for today's psu's. Here is my question. I am troubleshooting some pc's that have no post. I have the mobo on a piece of cardboard with standard, 1 stick memory, cpu, graphics card and using a screwdriver to bridge the startup pins. The fans turn on but there is no post so I went to check the psu with a psu tester and on 3 psu's the only light not lit was the -5v. So based on what was told to lowongas, I can assume that my psu's are not dead if the only light not lit is the -5v? I have swapped out ram, am using a known working cpu and gpu so I want to make sure that it is not the psu but perhaps a bad mobo.

What are your thoughts?

[mjc]

You do have to take into account age and CPU type when trying to figure out if -5V is needed or not.

[gracious]

Ahhh, that is true, so if these mobo's are say from the 2006 era, possibly I would need the -5v, so might have to find an older PSU or are there some new ones that still add the -5v?