iMac turns itself off?

[lisamel]

Hi!

I have had my iMac since 2007 I think and in the last 3 months it has started to just turn itself off and it wont come back on for hours. The first time it happened I was just writing something using Pages. The second time I was using iPhoto. And yesterday I was importing a videoclip from my camera. The iMac just switches off and I couldnt turn it back on until this morning. And when I did I started the importing again, and after about 20 minutes it was off again and I cant turn it back on now either. It has probably gone about 3 hours or so.

The first time it happened I took it down to an Apple reseller store but when they tried to turn it on it worked so they said that they could take it in and have a look, but if nothing was wrong with it I had to pay for it.

Now I was wondering if this has happened to anyone else? Is there anything I can do? Clean it or something?

I will try to call the apple reseller tomorrow and see what I should do. It has in been in for repair once before to fix the power supply unit.

Thank you

 

[Hellhammer]

Sounds like PSU or logic board issue... Try resetting PRAM and SMC

 

[lisamel]

Thank you. I tried the SMC one, but I still cannot turn it on, so I cant try the PRAM one but will do later if it will turn on