HUAWEI Mate 40 Pro Repair Cases

HUAWEI Mate 40 Pro Repair Cases Sharing

Cas 1

Cannot boot issue, the boot current curve is abnormal, fixed at 80mA.

This kind of issue, based on repair experience it’s normally caused by the CPU poor soldering. Finally, the issue gets fixed by CPU reballing.

Cas 2.

No display after very serious drop damage.

The Mate 40 Pro with double-layers motherboard design, for the drop damage issue. We can start by checking the connection between two layers of the motherboard.

After disassembling and checking, there are many pads with poor connections.

Fix the missing and poor soldering pads, then assemble the two layers of the motherboard. 

After testing, all functions are back to normal.

Cas 3.

Fingerprint function failure after screen replacement.

Check with the customer, the fingerprint (Touch ID) function failed after replacing a new screen, so the issue should either be caused by the flex cable damage or some components damaged by accident during screen replacement.

Check the fingerprint connector under the microscope carefully, and find a small component is missing.

Check the component on the bitmap, it’s a small resistor. So we can jump a wire to test first

After jumping the wire, the fingerprint function is back to normal.

Then find a new resistor with the same specification, and replace it. No fingerprint function issue gets fixed perfectly by resistor replacement.

Conseils :

When replacing parts like screen, battery, camera, etc. must pay special attention, an experienced repair technician or skill is required. do not damage the tiny components around it. A small component missing can cause a big problem.

Case 4.

Mate 40 Pro keeps restarting after dropping damage.

The phone just keeps restarting and can only enter into the system occasionally. After checking the PMU chip is extremely hot, the reboot should be caused by the power IC damage or poor soldering.

Reball the PMU, then assemble the phone to test, can boot normally.

(Better replace the PMU with a new one for stable performance, if you have a new PMU chip at hand)

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