Malfunction Phenomenon
The phone can be turned on normally, but the bottom speaker can’t work.
Trouble Shooting
iPhone X Bottom speaker No Working issue. Take apart the phone and run the cosmetic inspection of the motherboard. For this situation, we need to check pin 1 and pin 45 of the DOCK connector. The measured diode value is 5, which indicates that the bottom speaker is normal.
Continue to measure pin 1 and pin 45 of J6400 on the motherboard. The measured value of pin 1 is OL, which is normal. Judging by this, the pin 1 relevant circuit is open-circuited.
From the bitmap, pin 1 of J6400 is connected with pin D2 of U4900(speaker amplifier) by way of pin S162 on cylinders around the edge of the lower layer. Then detach two-layer from each other. There are multiple missed pads on the upper layer including pin S166 of the NFC circuit.
Then remove tins on the two layers and bonding pads with rosin soaked solder wick, and clean the bonding pads with PCB cleaner afterwards, the measured value of pin 162 is 570, which is normal.
Judging by this, the fault is related to the false solder of the lower layer. By the way, there are most of the pads are ground pads, so we just treat pin 166 with a jumper wire.
After finish the jumping wire, then make the upper layer and lower layer solder together, and assemble it and test again, problem resolved.
iPhone X Motherboard Repair Course
