Try using the earphones with the microphone attachment.
''If you can be heard all the time'' this proves that the voice transmission circuitry is OK but that there is a problem with the phone's microphone. It is either intermittently faulty itself or it has a loose connection to the systemboard.
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Here is a link to the Ifixit guide on how to replace the microphone in your phone.
''If you still experience the problem ''when using the earphones with the microphone attachment then there is a problem with the voice transmission circuitry in the systemboard.
Hi,
Try using the earphones with the microphone attachment.
''If you can be heard all the time'' this proves that the voice transmission circuitry is OK but that there is a problem with the phone's microphone. It is either intermittently faulty itself or it has a loose connection to the systemboard.
''If you still experience the problem ''when using the earphones with the microphone attachment then there is a problem with the voice transmission circuitry in the systemboard.