iPhone 6s Display Not Working - Black Screen - Diagnose and Repair Course.
The iPhone 6s has no display since its Back Light won’t work. We replace a new screen but problem still exists, and the current is normal. Hence, we conclude that the problem probably lies on the Logic Board.
There are four parts on Logic Board related to Back Light: C4023, C4020, FL4212 and FL4213. We test them one by one and find out that the inductor FL4213 is abnormal. We replace a new FL4213 and problem solved.