Question Monitor no longer working after disassembly and reassembly of motherboard (possibly a boot up issue)

Robo Reptile

Apr 18, 2016
System specs in my signature.

My computer was experiencing symptoms that seemed consistent with CPU overheating - sudden crashes to black screens while running graphics-intensive games, along with all my system fans suddenly running at max capacity - the system unwilling to respond to anything other than a forced shutdown.

So I pulled out my CPU, wiped it and its fan clean of the old thermal paste. Because of the way the CPU fan is connected, this required taking the motherboard out of the case, which required disconnecting all the wires and stuff. I also took the CPU out to clean it, then put it back in. So I did so, applied new thermal paste, put everything back the way it was (made sure that stuff like the Power Switch pegs were in the correct position).

Then the the troubles started.

My monitor remains completely and utterly dark whenever I switch my system on. Not even so much as a brief BIOS thing or a few flashing words. Nothing. It behaves as if there's nothing connected to the HDMI cable at all.

I've tried the obvious stuff - I've checked the HDMI cable at both ends, I've switched the cable between the Motherboard port and the GPU port, I've unplugged all extraneous stuff other than the monitor. No. Freaking. Dice.

There is one further oddity; when I switch on my system (which results in the fancy lights on the motherboard and GPU switching on and the CPU fan spinning), it stubbornly refuses to be switched off except by a forced shutdown (pressing and holding the power switch). This suggests to me that the issue might be with something other than my monitor.

Any suggestions?