Answer to: LCD Backlight not working = solvedOk, so I have just purchased a 2011 27 inch iMac. I have the black screen issue. Shining a torch on the display initially showed nothing. I checked leds and found I only had 3 lit up. I then removed the backlight inverter and cleaned some dry up crap of some of the solder joints, replaced and I now have 4 leds lit up and a faint image on the screen. Im going to remove the inverter again and put it under the magnifying glass and check all the joints and resolver if necessary. Maybe the common foul with the inverters might be just dry joints?