Chosen Solution

Alright fellow repairers, here’s a tough one : I repaired a broken screen on a completely destroyed iPhone 8 (both front and back glass smashed) - but the phone was still working perfectly. I made a chassis replacement, successfully. Then, I changed the screen, successfully also as usual. I let the phone charge (battery at 85% capacity), and come back an hour or so later : big surprise, the phone won’t turn on. I then start to disassemble it, and notice that the backlight of the phone is on ! The buttons are working, the phone even responds to touch : I could turn it off by sliding the power slider (blindly tho). Any idea of what could’ve go wrong there ? I tried another screen (Apple), the original screen (which was crappy af, had already been replaced for sure), but none worked. Even a DFU restore won’t help. Has any of you ever encountered that type of problem ? Is there a diagnosis that I can make to help ? I’m starting to have some micro soldering tools, can do some measurements for sure.

First check pins where you connect the screen they are very gentle than check components around it. Filters can be