I have a 500VA Patriot (brand) UPS that has been working fine for many
many years.

I have a "mini" computer hooked to it, one that uses a "mini" PSU
mounted above the CPU which is also used to cool the CPU. It is very
loud, so I decided to re-case the machine and use a standard PSU and the
machine is working fine. I have a separate fan for the CPU and it's a
lot quieter.

The only problem is the UPS, when turned on, interrogates , then goes to
fault. I have many UPS's and just used another and it works fine.



The Patriot is more of an industrial grade UPS and may have more safety
features than the consumer grade APC unit I'm using.


The only thing I can think of is that the mobo is putting some kind of a
"leakage" condition on the PSU.

As soon as I turn the UPS on, the machine goes on too, without pushing
the power switch.


Not a big deal just curious.