These three line paths which need to check first before attempting to replace the Digital Microphone Module.
Nokia C5 Microphone Failure Repair Solutionthe power management chip labeled as GAZOO. while the corresponding Data and Clock signal line paths is located near the CPU IC. There is a 47 ohms filter resistor is connected across the MIC clock signal, check and or replace it if found damaged or faulty.
If all the line paths is seems all okay, proceed to replace the MIC module.