Chosen Solution
I’m looking to buy a MacBook White A1342 but the screen is black and when connected to an external display works I just need to figure out how to know if its the LCD or the actual mother board so I can see if its actually fixable if the problem is the LCD (then it could be easily fixed) or if it is the mother board (then I wont fix it as it could be difficult and time consuming) Any answers welcome!
Take a flash light and shine it through the Apple logo on the lid, do you see the faint outlines of your desktop and its icons? If you do then the logic board backlight logic needs repairs, if not then you might have a bad LVDS cable or the logic board connection is bad or the display its self is bad.
