iPhone 6S issues: 2G No service and vibration not working

Trouble Phenomenon

 

The iPhone 6s fell into the water, the signal is good, but it can't make the phone call; 2G signal shows no service; the vibration function cannot be used.

Repair process

1. Power on iPhone, and test it, it has 3G and 4G signal, 2G signal is abnormal, it has no service.

2. Disassemble the iPhone 6s, take out the motherboard, and then connect it to DC power supply, we found it leaking 13mA, the water cell phone 2g signal is not normal. To observe a passing element under a VGA Digital Microscope, we found the R4501_RF resistance on 2G PA U2GPA_RF has been moldy, as shown in picture 9-9-1. Touch it lightly with tweezers, it fell down. The PP_VCC_MAIN through it supply power to U2GPA_RF, so it caused the 2G signal to be abnormal. Clean it up and weld it with solderingstation. After finish it, boot it and test it, the 2G signal is back to normal.

3. The vibration function of iPhone 6s is controlled by U3800 PA chip. Use multimeter to measure the diode data of tail socket, the result is normal. After we remove the U3800 PA chip, we found the solder pad is moldy, so we replace the U3800 PA chip, after that, no leakage when the phone is standby and the vibration function back to normal. The repairs end!