Malfunction Phenomenon
iPhone XR Half Dim and Half Bright.
Trouble Shooting
After we replaced another screen, the malfunction was still the same. Then we opened the schematics to check the backlight circuit. We could see the backlight circuit was similar to the iPhone P series models like 6 Plus or 7 Plus. There were two sets of backlight chipsets, U5650 and U5660, if one of the circuits was broken, half of the backlight LED will not work.
Then the screen could be half dim and half-bright.
We assembled the screen and turned on the phone, and checked the voltage on C5652 and C5662, normal value should be over 10V, if the value was just around 4V, it means the relevant circuit was damaged.
After we checked, we found the voltage on C5652 was abnormal, then we tried to replaced the backlight IC U5660 and tested again, the backlight function was back to normal.
Go to iPhone Motherboard Repair Course to Learn More.
