The client’s water-damaged iPhone 12 Pro cannot be booted, and it was sent to the repair shop after water damage for around 20 days.
Troubleshooting
First, disassemble the phone and take out the motherboard
- Remove the two screws on the bottom
- Place the phone on the heating platform, and set the heating temperature to around 70℃ to soft the glue between the screen and the frame
- Insert the slight card then the screen can be separated easily
There are two water damage indicators
- The one near the SIM card reader is fine
- The one near the earpiece speaker turned red
Which indicates the water or moisture is getting into the motherboard through the speaker mesh.
Protect the front camera, infrared camera, and dot projector first
Take out the screen and have a check, there’s no obvious damage on the screen
Then take out the motherboard and connect it with the DC power supply machine to have a check
It’s large connect once connected with DC power supply
It means there is a short on the motherboard. Let’s check the cosmetic of the motherboard under the microscope carefully again, the board looks fine, the components are clean, the motherboard does not get deformed, and the middle layer also with very nice soldering and connection.
After measuring, we find the PP_VDD_MAIN is shorted to ground
Connect with the DC power supply machine and observe under the thermal image camera, cannot find out the obvious shorted components. So the defect component must be located on the inner side.
We have to separate the motherboard with the heating platform and the hot air gun to check the inside components. After checking, we find something abnormal. The capacitor C413_E with two colors. Based on the repair experience, the inside of this capacitor must be damaged.
Remove the C413_E directly, and no need to solder it back
The reason of no need to solder it back
- It’s close to the middle layer on the left side, heat to solder it back may cause two layers poor connection
- On the right side is the Baseband CPU, if overheated, may also lead to baseband CPU poor soldering
- There are many other filter type resistors on the PP_VDD_MAIN, lost one won’t make a big difference
After removing this capacitor and measuring the diode value again, the short on the PP_VDD_MAIN is gone.
Then recombine the two layers of the motherboard and assemble the phone.
Power on to test, all the functions are OK.
The issue gets resolved by removing the filter type C413_E on the PP_VDD_MAIN
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