PC not turning on.

My sincere apogoly for (probably) posting this in the wrong section (if I did atleast).

I was playing a normal game of League of Legends a day or 4 ago with my friend on Skype, when suddenly my monitor's screen turned black saying there was no signal, my keyboard and mouse stopped giving light and there was no sound anymore either. My PC was still on (the light coming from my power button was still working), but I couldn't turn down my pc through the power button, so I forced it to shut down by pressing on the O button from the power supply. I pressed the button back to I, tried to turn my PC on again and nothing happend. There was literally no sign of life : The blue light that's supposed to come from my power button didn't work, I didn't hear any fan working, the PC does nothing at all. It's not making any beep sounds whatsoever.

So I was thinking of what the problem might have been. I thought it would've either been my motherboard that died on me or my power supply. I was testing if my power supply died by using a paper clip that was connected to the green and black wire. I did hear a boot sound but I didn't see any fan spin around. Is this a sign of a faulty power supply unit or could it still be my motherboard?

Computer specs :
RAM : Crucial Ballistix Tactical 2x 4GIG
Processor : Intel I5 4460 / 3.2 Ghz
Cooler : Gelid Tranquillo Rev. 2
Case : Cooler Master N300
HDD : Seagate Barracuda 1TB
Motherboard : MSI H81M-E35
Videocard : MSI R9 280 Gaming 3G Graphics Card
PSU : Seasonic S12II-Bronze 520W

Any help would be highly appreciated.

Kind regards,
Seiken.

Edit : I don't have a spare PSU unfortunately.

 

Well the only way to really tell is by using a dedicated PSU tester or another PSU which is known to be in good working order.
You can remove your PSU and take it to the local pc repairman, chances are they might do the testing for free.
However keep your finger crossed, because sometimes when a PSU goes bad, it can take the mobo with it.

 

Power Supply testers would only be accurate if they test the Power Supply under load. The best test is to Jump in a "Known Good Power Supply" Known good means a power supply that is know to power up a working system. I could very well be that the Power Supply is under powered for the system as well. Seasonic is a quality Brand.