Chosen Solution
Backlight will work if I take the screen brightness to minimum with F1 and then alternatively tapping F2 then F1 continuously. Is this a problem with the motherboard or screen inverter?
Diagnostics is never 100% straight forward, so i cannot say exactly what the fault is, but i can give you some tips to trace it further. Generally speaking, if the feed is coming from the logic board, then you can almost certainly say that its not the board. The logic has a built in backlight fuse, where if a short is detected, it will blow. This prevents any further damage to the board. This is typical if there is an overload, often caused by liquid damage or corrosion of some kind. If the board is intact, and you occasionally get backlight, as you suggested by alternately pressing the brightness keys, then it is likely to be an issue with the drivers of the backlight. On the earlier MacBook models, they use backlight tubes that are illuminated by an inverter board, which sits under the hinge cover in the display. The inverter cable runs through the left hinge, and can often get pinched if the hinges are loose. You can check if movement affects the backlight at all. Basically, the fault can be one of the following parts. Logic board. Inverter Cable. Inverter Board. LCD Panel. With the faults depiction, i’d suggest its one of the latter 3. If its the cable, you should be able to remove the top case and get the backlight to work by moving the cable (carefully, as you dont want to damage it further. If the inverter board or the LCD is at fault, then the only sure way of confirming this is to either run voltage tests on the outputs (with a voltage meter) or to have a known working part to fit to it for testing. If the inverter cable is not pinched or damaged, then i’d usually start with the inverter board. But thats just my experience. I hope this helps.
