I recently got a 2009 27 inch iMac. I noticed the display has weird thin transparent vertical lines shown in the photo below.

The lines don't obstruct anything, and are less visible the farther you are away, but they are annoying. The light and dark spots seem to me moving upward. There are about eight of these groups of 4/5 lines throughout the display about 1-2 inches apart with varying visibility. They are more visible on darker but not completely black backgrounds.

I plugged the iMac into an external display, and the lines were not there. Also, when I changed the screen resolution, the lines were in the same places. This makes me think it is not a gpu issue. While the computer was open, I pushed and pulled on some of the display wires and nothing happened. I also ran the mac with high cpu usage so it would get hot to see if anything would change, and it didn't.

When I opened it up, it appeared the locations of the lines corresponded with the ribbon cables that were going on the display

I found some other posts where people had the exact same issue (lines appearing in the same places), but they never solved the problem other than replacing the entire display.

What would cause this, and is it possible to fix without new parts? If it is the display failing, what specific part of it is? I might be able to get access to some pcb boards on a scrap iMac display to replace with.

vertical lines

Click for full size

1 Answer 1


Due to this occurring within the monitor itself. It is most likely a hardware issue, I think bringing it in somewhere and getting the display itself looked at is your best bet unfortunately.

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