Réparation du problème de démarrage impossible du HUAWEI Mate 40 Pro

Received a HUAWEI Mate 40 Pro cannot boot issue caused by traffic accident damage.

Modèle : HUAWEI Mate 40 Pro

Annoncé : 2020, 22 octobre

Phénomène de défaut

This phone was damaged in a car accident, and as we can see, even the middle frame has gotten deformed.

Disassemble the phone, we can find there’s a sticker, which means it has been repaired by another repair shop.

Besides, the motherboard has gotten deformed seriously, and the shielding cover on the CPU is missing.

Connect the motherboard with the DC power supply to have a check

There is no current leakage when connected with the DC power supply

Try to trigger with the DC power supply, the phone can be booted normally

Dépannage

Assemble the motherboard with another phone case with parts like the screen, vibrator, speaker, etc. connected. Then try to boot with the Machine d'alimentation en courant continu.

We can see the HUAWEI LOGO, the phone can be booted normally

So we can make a preliminary judgment that the issue might be caused by the battery or the battery relative circuit.

Since the HUAWEI Mate 40 Pro battery is encrypted, let’s connect the original battery to have a try.

This time, the phone can not be booted, is that possible the battery was damaged? Test the battery with the DC power supply machine, we can see the voltage on the battery is around 3.7V, normally, the phone can be booted by this voltage.

So the issue should still come from the motherboard.

Check the motherboard carefully again, we find below problems

1. the dock flex cable connector on the PCB is damaged (this won’t cause the does not boot issue)
2. one screw hole around the battery is missing (the underlines are looks fine)
3. a small component around the battery connector is missing

Check the bitmap, the small component is a resistor which is relative to the battery detection.

If this resistor is missing, then the battery information will not be able to transfer to the CPU and cause the phone cannot be booted.

So let’s solder back the small resistor to have a try.

It’s easy to solder back a new resistor with the same specification, but we find another small problem: one pad of the resistor on the PCB is missing.

The solution for this situation is short the resistor and the small component with some tin paste directly.

The short method as shown below.

In the next step, let’s solder back a new dock flex connector

Assembler et tester

After that, let’s cool down and clean the motherboard thoroughly. Then assemble it to have a test.

The phone can be booted normally with the original battery connected.