Chosen Solution
my iphone 7 screen is black but the backlight is on after a screen replacement. when i first connected the flex cables the apple logo DID show and turn on but the screen itself wouldn’t swipe etc so i disconnected and reconnected with the battery disconnected and went to turn it back on but i got stuck on the apple logo and the creen went black but the backlight was on. so i bought another screen and now both ofthem are black but he bcklight is on hheellppp!
By seeing that history of that something mishmash while change LCD.That problem accidently happen while putting LCD, while on on-condition or some parts that connect to LCD connector on PCB gone damage or remove while removing LCD. Better for the solution by my view. 1 - See the LCD connector pin ok. 2- First conform that without graphic phone detect by iTunes or Detect as DFU mode on iTunes. 3 - See the parts near LCD connector might be broken.
