Trouble phenomenon
There
is no sound during the call when it turn on speaker, but it has microphone,
and it frequently no service.
Troubleshoot
First, recording with voice function, 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.
Check the motherboard, we can find that the baseband 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.
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.
Power on the iPhone and show no service, we
can make sure that the baseband CPU is no problem. According 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.
After replace the 2G PA, it's 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.
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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