Power button not working... mobo issue?

[MilwaukeeMike]

Hey guys, I had some contractors doing some work on my house today and they needed to shut the circuit off to the room my computer was in. The computer was on at the time so it shut off when the power was cut. Now it won't go back on. Power button does nothing at all, and I don't know if it's the power supply, mobo, or switch.
I've got a power supply tester which causes my computers fans to start up when it's plugged in, so the power supply does respond. The results are in the attached file. It shows LL (which means to low to register) voltage for the -12V line. I honestly don't know if I even have that line so I don't know if that's bad. I attached the label on my power supply too. Would no voltage cause a computer to completely not respond? Because the fans DO start up when the power supply tester is plugged in.

I don't think the switch is the problem because I tried to short the power switch jumpers with a paper clip and nothing happened. I also took the CMOS battery out for a while and then tried it again and that didn't work.

Any ideas on whether I need a mobo or a power supply? I don't have an extra PSU around to test with, but I may try to find one before ordering a new mobo.

thanks in advance,
-mike

 

[SNGX1275]

Not the switch. Could be the motherboard or PSU, but I don't have any good insight.

I would unplug the PSU and flip the 120/240V switch to 240V, then flip it back before plugging it in. To me, this doesn't make any logical sense, but over about 16 years of playing with PCs I have seen it work twice.