Chosen Solution
I have changed the screen and battery on an iPhone 6s. I have changed probably hundreds of Apple lcds successfully. Here is what I know: Initially changed a smashed screen, the new screen worked but the phone was saying it needed to be reinstalled via iTunes. When trying to reseat the screen I could see that the battery was inflated, so ordered and fitted a new OEM battery. When rebooting, the screen was black but you could see a dim glow around the edges. iTunes picked up the phone but required me to put in the PIN no. I tried 2 other new screens wjth exactly the same result; no pictures but the phone is picked up by iTunes The new screen works on a different iPhone 6 Now here’s the really confusing thing: The iPhone boots and shows an image with the original (smashed) LCD! Any suggestions would be apreciated Cheers
Up until your second to last sentence, I was thinking “backlight circuit on the logic board”. However, if the original cracked screen works, then you probably just have a bad batch of replacement screens. Poor quality replacement screens maybe be pulling too much juice for the backlight and causing the circuit to shutdown or overload. This may or may not cause permanent damage to the components in that circuit. Perhaps the original screen allows the circuit to work just below their failure threshold. Ultimately, this has to be looked at by a micro-solderer.
