Computer dead?

Ok heres the deal, I built this computer for my father 2 years ago. Everything has worked fine until 9 months ago when the PSU went out, I replaced it and fine. Well now the darn thing wont post, boot up nothing. the screen will flash up "No signal" and then turns off. The keyboard and mouse don't even light up. All the fans on the computer work fine cpu, rear exhaust and top intake fans all work. I have even tested the Ram nothing. And to turn off the computer is even a task. I have to manual hit the switch on the rear of the PSU. I am leaning to a faulty MoBo. Any guesses? Thank you Its a Gigabyte mobo: Ga81945gzme-rh. and a intel 775 dual core processor.