iMac turns off and back on

[RyanMacUser]

I got a 20 inch imac around august or september of 2007. I noticed after about 8-9 months it would randomly restart itself. I wasn't on the computer much then so I really didn't care. I then got a laptop in 2009 and didn't use the iMac very much. It continues to restart itself though.

I read online that this was a known problem with this iMac and that it was a flaw in some of the hardware. I got Apple to replace something inside (I forget what it was now but I believe a circuit or something else along those lines) they even replaced it for free last year (years after I bought it) because it was a known problem.

This didn't work.

It continues to restart itself randomly. I am not sure if there is some screen shots I can post or what but if someone could help me out I would appreciate it, thanks.

 

[killerrobot]

It seems as though its cause is either a power supply issue or a logic board issue. Both of which are costly to replace.

https://discussions.apple.com/thread/2030379?start=15&tstart=0

A cheaper temporary fix is to install smcfan control to run the fans at higher rpms all the time. It alleviates the problem some, but doesn't solve it.

You could try to take it back to Apple since they have your repair history and see if they'll fix it again for free.