If you unplugged the screen without removing the battery it is very likely motherboard damage. The screen being black but illuminated sounds like backlight issues on the board which is fixable but requires soldering. Unplug the battery and screen and try to use a cotton bud and pure alcohol to clean the connectors on both the screen itself and the motherboard. Alcohol evaporates and is safe to use do not try cleaning the alcohol off with water or anything it will go by itself. If this doesn’t work you will probably need to replace a chip on the motherboard.