How to repair iPad 5 doesn’t boot issue

A customer sent an iPad 5 to repair, the phenomenon of failure is that when press the iPad power button, it has no response, the iPad touch screen is black. We need to disassemble it and check it.

The iPad display connector socket and the display line socket are damaged; also, there is a marked scorch mark at the boost inductor. After measure the diode data of iPad 5 socket, the boost inductor is the open circuit, the resistance of the other side is normal. Replace it with new display connector socket and display line socket, after installation, we found the inner display screen iPad backlight Diode can be lit, but no display on iPad screen, so the initial judgment is that the iPad screen is damaged.

Replace a new iPad LCD screen and assemble it. Measure it with Fluke 15B+ Digital Multimeter, now the iPad Tail plug detection signal has about 1.8V, and the screen can be lit after the iPad power on. We thought the issue has been solved. However, when inserting an Apple data cable to charge, the iPad percentage of battery charge has not changed. We suspect that the initial failure of the iPad 5 is that iPad 5 battery charge fails, power is missing, and then the iPad doesn't boot. Give it to someone else for repairs, after replacing the screen, the issue still exists, and we found several screws are not installed, the cover plate is missing and the wrong installation of the screen socket causes a short circuit, now has more failures.

Open the WUXINJI circuit diagram, and check the charging circuits, the key signals of each road are basically normal. At this time, we think Q8104 damage will lead to bad charging, so we directly use QUICK 861DW rework station to short solder the jumper wire on Q8104. After that, activate iPad battery, assemble the iPad, now the iPad can be recharged properly, other functions also works perfectly.