Hand built PC (The Beast) has just curled up and died.
Monitor went blank with no signal message, PC power button was flashing blue instead instead of solid blue, and would not power off.
After about 20 seconds, a series of clicks and then a big bang noise accompanied by nasty electrical type burning smell.
Haven't looked inside it yet.
So could be mobo fried, graphics card fried, PSU fried or a combination of any or all of those.
Autopsy tomorrow AM.