Iphone screen black but working?

Iphone screen black but working?

Added (1). My iphone screen went completely black but the phone is still on because i can feel it vibrating. I took it to a repair kiosk and she said it was probably the motherboard, can this easily be fixed? Its not the screen because its very very dim but i can still see it.

Try doing a manual reset. But your screen could be broken and you need to go to the store. Try plugging it into a computer.