Chosen Solution
iPhone that has its battery and display replaced a few months ago, a few weeks later it stopped working. After holding reset a few times eventually you could feel vibrations when flicking the ringer switch. I don’t remember what I did but it started working. Then a few days ago it again had a similar problem but this time the phone semeed dead until plugged into iTunes. In iTunes I was able to restore the phone multiple times but it still would not turn on but now would vibrate. I tried on the old screen and then the new screen and now there was a black screen as if the backlight is on but the display/touch is not. This is the same across two displays. I can feel vibrations when flicking the switch, I cannot check if it’s on Wi-Fi as it’s been reset. Now I’m left with a dead iPhone? If I press power to wake the phone the backlight turns on and that’s it. I’m quite lost.
Sounds like either damage on the screen connector on the logic board or the logic board needs micro-soldering / board-level repair work done to it. You’ll need to take the phone to a reputable repair shop that does board-level repairs to get it checked.
