"How to fix "vertical lines" on my iMac 27 late 2009"に関する回答I am pretty sure that the source of the problem is the controller board on the back of the lcd panel. It probably degrades with the heat produced by the gpu and cpu. I read pretty much all there is to read on the internet about that problem so my guess is that our lcd panels are fine but if we swapped just the controller board from a known working screen that has no lines, it would work perfectly. If i am right, finding a completely trashed imac on ebay just to use the controller board could be a cheap fix. I found the datasheet of the screen on google by searching for LM270WQ1-SDA2 (iMac Late 2009 i7 2.8). Sadly i am in no way able to understand and pinpoint what could be wrong by reading this but an electronics engineer or technician probably could. It could be a matter of replacing some surface mount capacitors who knows?