Huawei Mate 30 Pro has no signal repair

Huawei Mate 30 Pro has no signal repair

Machine model: 5G Huawei Mate 30 Pro
Customer’s description: The old mobile phone used for recycling, the original screen is broken, the new screen is replaced, and the mobile phone has no signal when it is turned on.
Test results: All functions of the mobile phone are normal, you can read Baseband IMEI, and you can read the SIM card, but you can’t find the signal, and the manual search for the operator failed.

Huawei Mate 30 Pro has no signal repair Figure 1.

Fault analysis: Because the screen of mobile phone is broken, it is mainly suspected that Inveracious Soldering, a cell phone signal related component, is damaged.
Open the Xinzhizao Soft software, find the Mate30 Pro annotation drawing,Boardview, schematic, and find the signal part.

Huawei Mate 30 Pro has no signal repair Figure 2.

Huawei Mate 30 Pro has no signal repair Figure 3.

First, observe whether the motherboard has obvious component damage, and then measure the working conditions of RF chip, including VCC,CLK and reset. Measurement shows that the 1.2V VCC of U4401 is not available. This VCC is transmitted by the power chip through the middle layer, and now only the upper and lower layers are separated.

Huawei Mate 30 Pro has no signal repair Figure 4.

Because the mobile phone was dropped, the middle layer pad break off was not found after separate, so the power chip was Repeat welding first.

Huawei Mate 30 Pro has no signal repair Figure 5.

After Repeat welding, re-welding, installation test and fault repair.

Huawei Mate 30 Pro has no signal repair Figure 6.