I have a 2009 27" i7 iMac. There was a little speck of dust that seems to have been between the lcd and the backlight on the top left corner of the screen, removing the glass and cleaning both the LCD and the inside part of the glass would not fix it. I took it to an apple store because of this and because my superdrive stopped reading DL DVDs. The genius told me that he would replace the drive and the LCD if necessary. After the repair the drive worked again and it was a different model than what originally came with the computer so I know that it was replaced.
The LCD screen did not have the speck of dirt anymore and looks great. After inspecting the computer inside to see if the screen had indeed been replaced, it turns out that the V-Sync cable is nowhere to be found and the screen still works! WTF? What does this V-Sync cable do? Where did it go? It was clearly there on the display connected to the computer before I took it in for service... I don't want to complain to the Apple store yet because the screen works.
The LCD screen did not have the speck of dirt anymore and looks great. After inspecting the computer inside to see if the screen had indeed been replaced, it turns out that the V-Sync cable is nowhere to be found and the screen still works! WTF? What does this V-Sync cable do? Where did it go? It was clearly there on the display connected to the computer before I took it in for service... I don't want to complain to the Apple store yet because the screen works.