When turn on iPhone 6, it shows nothing, only dark screen. But the screen is fine, so where is the real problem? Now, let’s follow the Vipprog to find the reason and fix it.
- Disassemble the iPhone 6, we can found that three screws are twisted deep. The problems are no backlight, no display and no ±5.7V power supply of screen. Observing under VGA digital microscope, we find that the four circuits under those screws are disconnected, as shown in picture 1-1.
- One of the four circuits is the open signal LCM_TO_CHESTNUT_PWR_EN of display power supply chip. This signal connects power supply chip U1202.
- The signal LCM_TO_CHESTNUT_PWR_EN connects display power supply chip U1501.
- The signal LCM_TO_CHESTNUT_PWR_EN connects display socket J2019 through the inductor FL2035, as shown in picture 1-2.
- After measuring, display socket has no diode data, which suggests that it is disconnected. We have to jump a wire, as shown in picture 1-3.
- After it can display, we measure other function and find that the receiver has no sound, but the diode data to ground of receiver is normal. Remove the audio chip (U0900) and measure the diode data. We find that pin C9 is disconnected. Pin C9 is connected to CPU (U0201), as shown in picture 1-4.
- Because CPU has not been fixed before, we guess that the disconnection of the circuits under screws causes the problem. Find a bare motherboard and scratch its surface (called grinding, as shown in picture 1-5). Thus we know that the second layer (arrow in picture 1-6) under screw causes problem.
- Next we jump a wire from audio chip pin C9 to the point that we find by grinding. At last, we paint UV Solder Resist to solidify it, as shown in picture 1-7.
- We skip other process of jumping wires, 10 wires in total. To operate in the same way.
Finally, after we do this all, turn on iPhone and it displays normally. The iPhone can back to normal work.