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ITThe HUAWEI P40 Pro is a high-end smartphone that delivers excellent performance, but improper charging can lead to serious problems, such as the phone refusing to boot. This particular case involves using a motorcycle charger, which likely damaged critical components related to charging and the USB circuit. Many users may think the only solution is to replace the entire motherboard, but with the right troubleshooting techniques and component-level repair, we can fix this issue effectively and at a lower cost.
This guide is perfect for technicians, DIY enthusiasts, and anyone looking to resolve charging issues in their HUAWEI P40 Pro without replacing the entire device.
Device Details
Model: HUAWEI P40 Pro
Announced: 2020, March 26
Defect Phenomenon
The phone was charged using a motorcycle charger, which resulted in the device being unable to boot. The cause was likely a malfunctioning charger or improper charging operation, leading to damage in the phone’s charging circuits.
Troubleshooting
1: Initial Assumptions
- Since the problem is charging-related, we can reasonably assume the issue stems from either the USB circuit or charging IC.
2: Disassembling the Phone
- Begin by disassembling the phone. Ensure the cameras are protected with stickers and carefully remove the motherboard.
3: Testing for Current Leakage
- Solder a wire onto the motherboard and connect it to the positive clamp of a DC power supply.
- Trigger the boot process, and observe a 42mA current leakage, indicating potential chip damage causing overheating.
4: Thermal Imaging
- Use a thermal imager with the DC power supply connected to locate the overheated chip.
- The thermal image reveals that the charging IC is the culprit, and its thermal grease has already turned black, confirming the damage.
5: Charging IC Removal
- Apply solder paste to the charging IC area and heat it with a hot air gun to remove the faulty IC.
- Clean the PCB pads using solder wick and reball a new charging IC.
- Solder the new charging IC back onto the motherboard.
6: Testing for Current Stability
- Connect the DC power supply again and verify that the current leakage has disappeared.
- The boot current curve returns to normal, confirming that the charging IC replacement resolved the booting issue.
Charging Issue Diagnosis and Repair
Although the phone now boots up properly, it still does not charge. The next step is to troubleshoot the charging system:
1: Dock Flex Cable Check
- Measure the 5V charging voltage on the dock flex cable and confirm that the correct voltage is present.
2: Diode Value Measurement
- Measure the diode value on the 5V voltage rail of the motherboard. A low value is observed, indicating a further issue in the charging circuit.
3: Filter Capacitor Removal
- Remove the black glue around the connector. Based on repair experience, remove the filter capacitor near the charging connector to test if it resolves the low diode value.
- The diode value remains low, indicating the problem lies deeper in the circuitry.
Signal Board and Additional Chip Replacement
To identify the root cause of the charging issue, we need to inspect the signal board:
1: Motherboard Separation
- Separate the two layers of the motherboard to inspect the signal board.
- Identify three damaged chips, including a burned MOSFET and two other components, as seen under the red circles.
2: Chip Replacement
- Replace all three damaged chips.
- For the MOSFET, some PCB pads are damaged, requiring a jump wire to bypass the missing pad.
3: Reassembly
- Recombine the two layers of the motherboard.
- Assemble the phone and run a final test to ensure everything is working.
Final Test and Results
After completing the repairs
- Booting Functionality: The phone successfully boots up without any current leakage.
- Charging Restored: The charging function is fully operational, allowing the phone to charge normally once again.
Conclusion
When a HUAWEI P40 Pro won’t boot or charge due to improper charging, many assume the entire motherboard needs replacement. However, through precise troubleshooting and component-level repair, the charging IC and other damaged components can be replaced, restoring full functionality to the device. This guide demonstrates that detailed analysis and targeted repairs can save both time and money.
If you’ve encountered similar charging issues or would like further clarification on the steps mentioned, feel free to reach out or leave a comment below!
