Tips for iPhone 6 microphone not working well

The function of audio on iPhone are normal, such as receiver and hand-free all is normal.The calling is normal through earphones. The only problem is the sound from the microphone (on Charge Jack) is low. This iPhone has been changed audio frequency chip, audio amplifier and USB Charging Port Jack. So, what is the problem? Vipprog gave a guide.

First, teardown the iPhone 6 by phone repair tools, and then remove the motherboard. We can see that audio chip and audio amplifier have been soldered, to be on the safe side, we replace the chip directly.

Second, after changing the audio chip, the problem is still the same. We can exclude that Charge Jack and audio chip do not cause low sound from the microphone. It is the miscommunication between two microphones signal LOWERMIC1_TO_CODEC_P and LOWERMIC1_TO_CODEC_N and audio chip that cause that problem. Two coupling capacitors C0922 and C0923 are often broken. The location of C0922 and C0923 in bitmap is shown in picture 1-1 and the material objects of C0922 and C0923 are shown in picture 1-2.

Third, judging from the exterior, the two inductors are normal. Using multimeter to measure the diode data to ground of its one end toward the big audio frequency and the data is normal. Use a jumper wire to short connect the two inductors and test the sound from microphone, but the sound is still low. Based on previous experience, in addition to the damaged inductors, the problems may lie in the four signals PP_GPIO0, PP_GPIO2, PP_GPIO and PP_GPIO4 which are from Charge Jack socket to baseband and power supply PP_BB_VDD_27 (picture 1-3). The material objects are shown in picture 1-4. The diode data to ground of the four signals measured on Charge Jack socket is about 450 and the diode data to ground of the 2.7V power supply is about 750. The above data is normal.

Finally, check the Charge Jack port. Directly replace the rear cover assembly and test again. The sound from microphone is normal now. So we replace the Charge Jack and assemble motherboard to test. The sound from microphone is low now but when testing on rear cover assembly, it is normal. After checking circuit diagram, we know that there is the other microphone on rear cover assembly. This microphone is on the power button cable. Assemble the motherboard to the iPhone assembly and use a tweezers to short connect the power signal cable to turn on it. Get into IOS and test. The sound from microphone is normal now.