My Problem
The graficchip looks like defect. But its mounted on the Logicboard. So first tried to backe the board (may the Chip could have some contact problems.) But didn't fix the Problem. So the board was to expencive to replace, so i get th HD away from the MacBook to backup the userdate via USB-SATA-Bridge to a iMac
My Fix
The Magnetizer/Dema
My Advice
Look very carfully for the place of every screws at the MacBook - also some inside - to open the cover. See at the other Advice to replace the Board
Written