Is it the psu.

[opstrat]

Left the machine running last night to download.

Woke up to find it off.

Done a quick paperclip test failed that. Changed the kettle lead thinking it was the fuse, didn't work.

Automatically I'm thinking the psu is dead, but I noticed my corsair headset was lit up, is that possible?

Edit corsair ax850 psu.

 

[Ceryndrion]

Double check the paperclip test, just to be sure, make sure you have at least 1 fan connected to it so that there is some sort of load.

If your USB devices are still receiving power, then the psu isn't entirely dead, just mostly dead.