No video signal to the Monitor

Hey guys

Last night when I was editing a video, my pc (HP pro Desktop) decided to shut down. There was no flicker on the screen or error what so ever. I instantly tried to boot it up but the power button usually has LED light on but this time has nothing. The fan were running but there was no video out on the monitor. I researched the problem and triad everything but nothing works.

I triad replacing the ram with a new one, the video card, the CMOS battery even resetting the bios also switching to the on board VGA video output. The DVD drive works fine. I am not sure if the problem is the motherboard, I hope it is not the motherboard. Any solution to this would greatly be appreciated.

Please help.