Chosen Solution
I have an iMac13,1 with a very faulty display that just shows vertical lines and noise. The iMac works fine with an external display, and I can use it just fine in mirrored mode. I have removed and re-seated the LVDS cable, but that hasn’t helped. Based on this picture, is it more likely to be a problem with the cable, or the display itself? iMac Display Issue
Looks like a faulty display to me. But you should try another cable first, wich is not expensive. Good luck!
