Ursprünglicher Beitrag von: Kelly Boss ,
Sounds to me like a power supply issue. Did it smell electrical or metallic? I would recommend opening up the iMac and checking the capacitors on the power supply. There may be some bulging capacitors on the power supply that have either exploded or have failed. Based on the information provided in the comments, I would recommend replacing it with [product|IF168-004|this] power supply. Hope that helps!