I have this issue in my mid 2010 2.93ghz i7 iMac. I just replaced the backlight board this morning and its still exactly the same. The LCD is displaying an image, but the backlight wont stay on. Any ideas? Do i need to replace the LDVS cable now? Update (03/11/2019): PS. I can get the backlight to come on briefly with the shift-ctrl-eject keystroke. But it doesnt stay on for more than a couple of seconds. This is with the old backlight board and the new one. Surely the LDVS cable wouldn’t react to a keystroke like this? What else could it be?