computer boots up for 2 seconds then shuts down

[Treeroy]

I've just installed a new cpu and motherboard. When I turn the pc on, it shuts down after 1-2 seconds. It then turns itself on again and this happens a few times.

I'm thinking I may have not plugged something in?
What is the problem?

 

[shortstuff_mt]

This troubleshooting checklist was created for this type of problem.

 

[Treeroy]

Well that was embarrassingly simple. I hadn't plugged in the cpu power cable.

In my defence, I had looked at the cable and wondered where it had to be plugged in! 😀

Thanks, lifesaver.