My iMac 24" (mid 2006) is dead. It has been hard to get out of sleep mode in a month, and needed several restarts to start up. Now its dead. I hear the fan starting, but stops immidiately afterwards. I have looked at the diagnose LEDS inside. Number 1 is light on, the next three lights up at start but goes out immediately after. I have googled and found that it is either the power Supply or the logic board. But which?? Hope someone can help me diagnose which of the two. Thank you!