The following solution is for Nokia 5230 MIC(microphone) mouthpiece failure or not working problem. The solution below provides some simple steps on how to fix the the 5230 microphone problem.
1. Try restore, the device firmware or flash update to the latest available version.
2. Replace the 5-pin digital microphone.
3. Check the VMIC supply voltage, if already replace but the problem still exists.
4. Check replace the resistors and capacitors.
5. Rework AVILMA IC, replace if necessary, then re-flash the phone again to its firmware version.