iPhone 6 Plus front camera and screen problem (mainboard)
I'm doing Apple repairs for about ten years, but I've never had similar case. So I got an iPhone 6 Plus with not working front camera. First - I've replaced flex with new one, but front camera still stays black (back camera is OK). I've checked it on another 6 Plus and worked fine there. After that, I checked all connectors - they look fine, untouched. So next suspects were FL1123 and FL1144 - they have continuity. I've checked filters FL1112, FL1113, FL1114, FL1115 - they also have continuity, but the schematic says they have to be 120OHM. I got different reading on each, never reached 120OHM (max was 34OHM). I've also decided to check U2301, which is responsible for front and back camera. I removed it and jumped pins 1 and 2, just for testing. No success, front camera stays black, even with another flex. The voltage on C2301 and pin 1 of U2301 is ~3,5v. Isn't it too low? Shouldn't be around 4v?
I've been doing all checks etc. with my known good test screen. I decided to put the original screen back and what? It doesn't work. Phone turns on but have no image. Ok, it could be my bad, I could damage flex etc. BUT after connecting it to another 6 Plus it works perfectly. I connect it back to to repaired iPhone and it doesn't work. I've tried 5 different screens and all works except the original one, with which I got the iPhone. Do you have any suggestions what could cause this problem?
Thank you for your help!