Chosen Solution
I’ve recently replaced my laptop logic board as there was a number of issues with the early 2015 MacBook like keyboard backlight not working and fans running full speed, but the main reason being the backlight not working. I can see the LCD working when I shine a flashlight through it and works with an external display. After logic board replacement, the laptop nearly works fine except for the display backlight. Could a faulty LVDS cable be a possible issue?
Yes it can, the power for the backlight runs through the eDP/iDP cable. I’ll say it’s pretty uncommon, but it’s possible. Since you already replaced the logic board, the only other possibilities is the eDP/iDP cable or the backlight itself and the eDP/iDP is a lot less expensive to replace than the screen assembly.
