Huawei Honor 20 can’t make a call

Huawei Honor 20 can’t make a call

Machine model: Huawei Honor 20
Symptoms: The customer described that sometimes I couldn’t get through when I called, the 4G signal was full, but the signal would skip one cell, sometimes no serviecs.
Actual measurement: sometimes the signal of the plug-in test mobile phone is very weak, sometimes the 4G display is normal, the mobile phone can’t make a call, and the call fails.
Solution:
When the motherboard is removed, it is found that the shielding covers of the signal part of the motherboard have been removed, and all the chips of RF signal part have been passed by welding. During the test, the position of RF power amplifier U4601 is very hot by sensing the temperature with the hand feeling method. In the boot state,The rosin smoke method finds that the surface RF melts quickly, as shown in the following figure:

Huawei Honor 20 can’t make a call Figure 1.

Huawei Honor 20 can’t make a call Figure 2.

Huawei Honor 20 can’t make a call Figure 3.

After removing power amplifier and replacing it, the test signal is stronger than before, but it will jump to only two frames, which is not very stable. So we found power amplifier power amplifier IC, took down the chip, put short-circuit in and out, and tested the signal strength again. Compared with other Android phone signals, it was confirmed that the signal returned to normal, and the call was normal, and the fault was repaired.