Customer send us a iPhone 6 that is no sound on the phone call when it turn on speaker, but it has microphone, and it frequently no service.
1. we find the voice function has no problem, and the earpiece has sound, so we can concluded that the circuit from audio to earpiece is fine which can exclude the problem of audio. Then the problem maybe is signal of baseband CPU sends to audio.
2. Check the motherboard, we can find that the ba seband CPU and the IMEI was repaired, probably the problem is on the baseband CPU. Remove the baseband CPU with hot air gun, we can find that there are many pins was lost, as shown in picture 4-3-1.
3. Because there are many pins lost, so possibly the iPhone 6 dropped before. Check it more carefully, there are two useful pins was lost. Put motherboard under the microscope, use jump wire to solder U1 pin V1 pin, and painted with UV Solder Resist Mask, then install baseband CPU.
4. Power on the iPhone and show no service, we can make sure that the baseband CPU is no problem. Acco rding to the experience, after change baseband CPU but still no service, so we can choose to replace the 2G PA, as shown in picture 4-3-2.
5. After replace the 2G PA, its still no service, but the phone has display operator, it means the signal of receive is good, the problem maybe is in the part of the emission. So, replace the big Radio frequency, as shown in picture 4-3-3.
6. Finally, after replace the big Radio frequency, the signal is fine, and the phone call is normal. As shown in picture 4-3-4.
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