Wish I had an idea what to tell you. I never much worked on broken iMacs. Never owned one at MacGurus and about the only thing I have dine to customer units is replace stuff - drives, power supply, that kind of thing. I was hoping someone who knew your machine would pop up, doesn't appear so though. My apologies.
"I am a mortal enemy to arbitrary government and unlimited power. I am naturally very jealous for the rights and liberties of my country, and the least encroachment of those invaluable privileges is apt to make my blood boil."