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Hi, I’m having a screen/display issue which occurs immediately when my iMac is powered on. It's a late 2009 21.5 inch...

I managed to solve the displaying issue. As it seemed to be a video card issue, and the connector did not seem to be the problem, I finally tried the process of re-flowing the solder of the video card by baking the video card in the oven. Yes! The card is repaired by puting it in the oven for 8 minutes at 190 degrees celsius, after removing all stuff from it that can melt (thermal paste, rubber). It is described on many forums on the internet and also here: Temporarily Repair a Lost Cause Graphics Card by Heating it up in an oven After assembling the iMac, the screen is functioning great again. I hope that someone will be helped by this thread. But beware: It is at your own risk