Starts to boot then switches off halfway through loading os
crwdns2934249:0crwdne2934249:0:
Have changed ram and hard drive.
New install of yosemite.
But not so,ved the problem...it starts to load .it gets about a third through and then machine switches off.it is plugged into mains.
Tried safe mode and pram zap but no joy.
Any ideas?