I have a gigabyte 790x and everything was going fine until I had an emergency at the house and had to shutoff the Switches on my House electricity. When I turned them back on and went to my computer room my pc would only turn on but my monitor wont post anything. I already checked my videocard, my memory and my psu on my other computer wich just leaves me with the mobo. Did I killed it when I turned off the electricity like that? I know it was dumb but it was an emergency I guess I need a power surge next time. thing is My other also got shutoff but its fine.
I have another computer. I installed the power supply, then the videocard, cpu and memory. they all seem to work just fine. Just not on my motherboard. It powers up my videocard my cpu and even my keyboard blinks just as if it would boot but its just a black screen.
If I understand you correctly, the psu, vid card, cpu, and memory can each be individually installed in another PC, and that PC works.
So, the problem is in your motherboard. Reset CMOS (pull plug on psu, remove battery, press the case power on several times, use the clear CMOS jumper on the mobo if you have one, wait ten minutes, put battery back in).
If that allows you to get into BIOS, restore defaults, etc.