Reballing (actually replacing but doesn't matter but in this specific case the outcome is the same) the GMUX on a MacBook Pro 15" 2010 board model number 820-2850 to fix artifacts on the internal LCD.

Artifacts show up as pink lines on white background and green noise on black background, these are an indication of an LVDS signal issue. They show up both when using the iGPU and the dGPU so it's not a GPU problem.
Pressing down on the GMUX makes the artifact go away, which confirms a contact issue under the GMUX, probably due to the machine having been dropped.

Please don't make me say what I did not, we're reballing a GMUX here, not a GPU. When there's a GPU related issue, in the vast majority of the cases it's not an contact issue between the GPU chip and the board, but rather a defect of the GPU IC itself. Reballing is pointless (just heating to 200°C for a minute and a half often brings it back to life but it'll fail again soon), GPU chip has to be replaced.

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