Chosen Solution
The Main in built screen does not give any display what so ever, its completely black. The unit turns on and gives the start up sound. It also can display to a external monitor connected through thunder bolt. I have replaced the screen with no luck and I have also replaced the led driver board with no luck. the logic board shows 4 green lights as well. any help would be appreciated!
Open it up and check if the LVDS (display data cable) is damaged or loose. Try a known good display data cable. If this fails replace the LCD.
