Malfunction Phenomenon
iPhone 7 Plus Ringtone Not Working, and the voice recording function also abnormal.
Trouble Shooting
Disassemble the phone and checked the audio circuit, the motherboard looked good. Continue to measure the power supply for the audio IC U3101, there are 4 sets of power for the audio IC. We can measure the below voltages:
- Measure PP1V8_VA on C3209
- Measure PP1V8_SDRAM on C3211
- Measure PP1V2_VD_FILT on C3217
- Measure PP_VDD_BOOST on C3212
After measurement, all of the values are normal.
Judging by this, the power supply for the audio IC was normal.
Then remove the audio IC and checked the pads, all pads seemed normal, replace another audio IC and test, audio function back to normal, the problem was resolved.
Tips, the common issue for iPhone 7/7P audio function is from the connection between the pads under audio IC U3101 and the small components around it, especially the pad C12 to R1103, which nearby the motherboard gap.
We can repair it by jumping a wire between the pad and the component.
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