Mac go's in to boot loop

At first the Mac keeps going in boot loop so I did some troulshooting with a Mac tec support. He said my hard drive was bad. we went in to disk utility and tried to repair, then clean the hard drive nothing worked. So I replaced the hard drive that I bought from you guys. still the same thing. By persistently restarting it I got the formatting done and loaded OS X loaded with a CD-disk.Sometimes it will run a wile like 10 min then it reboots over and over with out a brake in time, just blue then gray then black then gray and black over and over.

I'm thinking power supply Or am I on the wrong track.

If there is any one with the same thing going on i would appreciate some feed back.

I went to what looked like web sight for troubleshooting and did all the steps again nothing.:(

hear is the web sight

https://techtalktone.wordpress.com/2013/...