iPhone X has no sound due to water ingress

iPhone X has no sound due to water ingress

Machine model: iPhone X

Malfunction: the phone has no sound, and enters the setting function runs slow.

Maintenance process: disassemble the machine and observe that the display screen of the motherboard has been replaced, but it has not been repaired. When it is powered on, there is 50mA short-circuit current current, which is directly locked as coder circuit failure.
The main board separate, the logic board is relatively clean, and there is no trace of corrode. It is no longer short-circuit current to power on the logic board alone, so the fault point is on RF board.

iPhone X has no sound due to water ingress Figure 1.

Observing the RF board, the ring amplifier IC U4900,earpiece amplifier IC U5000, and corrode around wireless charging IC U3400 are serious. After Repeat welding is carried out on the parts of corrode, it is found that U4900 can’t be returned to its original position. When this IC is removed,corrode is particularly serious. Replace it with a brand new ring amplifier IC.

iPhone X has no sound due to water ingress Figure 2.

Test the machine with the test stand and find that the machine is no longer runs slow, but there is still no bell.

iPhone X has no sound due to water ingress Figure 3.

Pass the diode value around the ring amplifier IC, and find that the shorted to ground at the second end of the resistor R3421 leads directly to the S27 pin of the column, which is the EN from the power supply to the wireless charging IC, and it has nothing to do with the ring. It seems that the electrolyte of water damage caused Short circuit, and Flux was added next to the column, and SMD REWORK STATION 300-degree blow welding on the column, and Short circuit disappeared.
On the test stand again, there is still no bell. In order to eliminate the fault caused by Accessories,earpiece FPC was buckled and tested, and it was found that the bell on earpiece was normal. Check with replacement method, find that the rear horn is broken, and remove all faults after replacement.

iPhone X has no sound due to water ingress Figure 4.

The bell of this machine is sent to earpiece horn through U5000, and the other is sent to the bottom horn through U4900. The bottom horn of this machine is broken, which leads to a detour in maintenance.