How to fix iPhone 7 turn on failure

Fault Description: iPhone 7 happens broken seriously and caused to cannot be turned on.

Meanwhile, during we check it, we found that the screw posts fell off. But we check the current, which shows the motherboard works well, so we need to check other place.

First, try to power up, we found a large current leakage, and continue to test by digital multimeter , we know the 3V power supply short circuit. Observe seriously, the motherboard card slot position is bent, and the short circuit may be in this position. Remove the two capacitors next to the NAND flash by QUICK 861DW Hot Air Rework Station and power on, the phone turn on normally.

 Test function after turned on, we found no Wifi, sometimes stuck when enter the settings. When check, the Wifi clock signal R0807 end has 1.8V, the other end through the Wifi module 17 pin have no voltage, we replace the resistor, but the fault remains. Remove the iPhone Wifi IC, the soldering pad drop the point.

Originally, we plan to turn on phone without install the Wifi module,  and test its function. But there is leakage when power-up, we have to apply rosin. After removing the heating capacitor and test, the setting function is normal, no longer stuck, next install the WiFi module.

After the installation, test again, WiFi appears, and the problem of stuck setting have been solved, but sometimes appeared restart. Considering that the middle position of the motherboard occues bent, the iPhone Audio IC will cause a restart phenomenon, so we have to disassemble the audio. After replanted fly line, all functions tested normal. The next step is to change the match.

Replace the iPhone fingerprint flex cable on the phone. Then install the repaired motherboard, test function after turned on, all function recovers normal, phone fault repair end.