Monitor Says ''No Video Input'' :(

Hello guys,

Recently I bumped into this problem that my monitor started to give me a msg that said ''No Video Input'' this happened after my pc randomly shut down.

I thought the problem was with my motherboard and bought a new one but still the same problem, starts up, everything is spinning but no power is going to the keyboard/mouse & on my monitor it keeps saying No Video Input.

Also I just noticed my mobo doesn't beeps when I have no ram in it and there's no lamp that gets on.

-What I tried-
Switched PSU
Switched Ram/Diff Sockets
Switched Graphics Card
Use the MOBO graphics card
Test my 2 monitors on diff pc's (they work)

-Didn't tried yet-
Switching CPU
Switching Hard Drive
Switching ...?

Any suggestions what's going on/What could be the problem.

/Specs (What I know so far, will write more tomorrow when I wake up)
Mobo- msi b75MA-p45
PSU- Corsair 600W
CPU- I7 3770k
Graphics Card - gtx660 or gtx550ti or mobo graphics card

-Zenix