Responder a:LCD Backlight not working = solvedI would suggest never going back to the repair shop that did not even open the iMac and told you it was the LCD or the MLB. I am an Apple Consultant and also repair only Apple computers, so I have been in quite a few iMacs. Usually ends up being the backlight board but always check the cables because I have had 2 that I can remember where another repair shop and even the Apple Store had done a repair not related to video issues but messed up the v-sync cable. The v-sync cable is very delicate and you can easily mess the pins up or crimp the cable causing intermittent or total loss of backlight. I know you have solved your issues but thought I would add this for anyone else searching on how to fix this problem.