PSU dead ?

[Toasty]

Ok so I went to switch my pc on today and nothing happened.

System is an 3770k @4.5 on a z77 sabertooth with 2 670's in SLI, PSU is the XFX 1250W.

So I tried the lead in another supply and that was ok.

I then removed the PSU and mobo and tried to power up on the mobo box, again nothing.

I then tried the psu in another old system and it managed to click once turn the fans slightly and that was all she wrote.

I then tried powering my main system with a 7850 installed with a different supply and it ran without problems.

This system has been running for a year with no problems, I really am shocked that the PSU has went like this, when it is supposed to be one of the best.

Any thoughts that would indicate that its not the PSU?

 

[Toasty]

Hmmmm psu powers the fan using paperclip but was no-go with the system.

No switches or jumpers etc have been moved the system was powered off lastnight.

 

[Toasty]

Yes i tried using it to power a box that has been lying there for a while and it clicked and moved the cpu fan a little and then nothing. Maybe it can power a fan but any proper load on it and it dies?