How to Fix Huawei Mate 40 Pro Keeps Restarting

Imagine a scenario where a Huawei Mate 40 Pro keeps restarting because of significant drop damage, resulting in a cracked screen and visible liquid crystal leakage. As a consequence, the phone continuously reboots, displaying the HUAWEI logo for a brief moment before shutting off again. In this blog, we will explore potential repairs to address this challenging issue and help you get your Huawei Mate 40 Pro back to optimal functionality.

Phone Details:

Model: HUAWEI Mate 40 Pro

Announced: 2020, October 22

Why Huawei Mate 40 Pro Keeps Restarting

A Huawei Mate 40 Pro that has sustained serious drop damage is experiencing a persistent restarting issue. The screen is cracked, with visible liquid crystal leakage. When attempting to start the phone, it continuously reboots, showing the HUAWEI logo for a second before shutting off again.

Troubleshooting

1: Disassemble the Phone

• Begin by removing the back cover. Due to the severe drop damage, the cover should come off easily.
• Remove the screws securing the motherboard using a screwdriver.

Carefully separate the wireless charging coil module. Be cautious of the hidden flex cable to avoid damaging it.

2: Screen Test

• Replace the damaged screen with a new, functioning screen to test the device.
• The phone continues to reboot, indicating that the problem is not with the screen but with the motherboard.

3: Identifying the Root Cause

Based on repair experience, a common cause of the rebooting issue in such cases is poor soldering or loosening of buck inductors on the motherboard.

Repair Process

1: Inspect the Buck Inductors:

• Remove the shielding covers from the motherboard to expose the components.
• Focus on the buck inductors around the Power Management Integrated Circuit (PMIC).
• Use a tweezer or blade knife to gently pry the inductors, checking for any that are loose or poorly soldered.

2: Identify Loose Components:

• Due to the PCB design, small inductors around the chip can easily become loose or poorly soldered after serious drop damage.
• If an inductor or other small component drops off easily when pressed, it indicates poor soldering.

3: Resolder the Loose Inductors:

• Thoroughly check all the inductors around the PMIC.
• Resolder any loose or detached inductors and components back onto the motherboard.

4: Reassemble and Test:

• Replace the damaged screen with a new one and reassemble the phone.
• Test the device to ensure it boots normally and all functions are operational.

Conclusion

The restarting issue on the Huawei Mate 40 Pro, caused by drop damage, was resolved by identifying and resoldering the loosened buck inductors on the motherboard. This repair demonstrates the importance of repair experience and steady handwork in addition to theoretical knowledge and troubleshooting logic. Accumulating hands-on experience and refining soldering skills are crucial for successful repairs.