Huawei Mate 30 Pro mobile phone has no signal, and the search operator failed to repair it

Huawei Mate 30 Pro mobile phone has no signal, and the search operator failed to repair it

The resistance value of one end of C1226 main power supply is also about 400. The main board has been changed, and it must have fallen before. The main board has no deformation area, so the main power supply is basically locked or the middle layer is soldered.

Machine model: Huawei Mate 30 Pro

Fault symptom: Mobile phone search operator failed.

Maintenance process:

A Huawei mate30 Pro, with a new screen, has no signal when it is turned on. It has both baseband version and serial number, and can also read cards. Manual search for operators failed.

Huawei Mate 30 Pro mobile phone has no signal, and the search operator failed to repair Figure 1.

Kirin model, the search operator failed mostly because the intermediate frequency working conditions were not met, so the intermediate frequency was replaced first, and the fault remained.

At this time, there are two maintenance directions: the first is that the working conditions of the intermediate frequency are not met; The second is caused by virtual welding in the middle layer. Remove the IF, and measure 8 channels of communication between IF foot and CPU, and find that the resistance is normal. Intermediate frequency, CPU and their communication are basically excluded.

Huawei Mate 30 Pro mobile phone has no signal, and the search operator failed to repair Figure 2.

Huawei Mate 30 Pro mobile phone has no signal, and the search operator failed to repair Figure 3.

Huawei Mate 30 Pro mobile phone has no signal, and the search operator failed to repair Figure 4.

Huawei Mate 30 Pro mobile phone has no signal, and the search operator failed to repair Figure 5.

Looking at the drawings of the CPU module again, it is found that there are two circuits below the IF communication circuit. The first circuit [PMUO_RF1_CLK] is that the CPU is connected to the main power supply.

Huawei Mate 30 Pro mobile phone has no signal, and the search operator failed to repair Figure 6.

Remove the L601 measuring CPU, and the resistance at one end is about 370.

Huawei Mate 30 Pro mobile phone has no signal, and the search operator failed to repair Figure 7.

The other end of the test is OL, because it has to pass through a coupling capacitor to the main power supply to make up the inductance L601.

Huawei Mate 30 Pro mobile phone has no signal, and the search operator failed to repair Figure 8.

Huawei Mate 30 Pro mobile phone has no signal, and the search operator failed to repair Figure 9.

The resistance value of one end of C1226 main power supply is also about 400. The main board has been changed, and it must have fallen before. The main board has no deformation area, so the main power supply is basically locked or the middle layer is soldered.

Huawei Mate 30 Pro mobile phone has no signal, and the search operator failed to repair Figure 10.

Welding the main power supply in layers. Start-up test, there is a signal, and the maintenance is over.

Huawei Mate 30 Pro mobile phone has no signal, and the search operator failed to repair Figure 11.