Had the same problem, computer crashed. It would not boot up with no signal error. Tried all the steps here but none worked for me. After a few hours tinkering, I disconnected my graphics card completely and was then able to boot up as normal with my HDMI output on the motherboard. Tried reconnecting the graphics card and was once again unable to boot so it's definitely the problem. Motherboard output is rubbish! Looks like I will be investing in a new graphics card.
If none of the other steps work for you, try removing the graphics card and if it's at fault, it should boot up!
Thanks to everyone for your solutions. Knowledge is best shared!