If you ever open up your device, you will see a green board called as the Printed Circuit Board, or the PCB. PCB is important for your device as it connect one parts to another, resulting in signals, voltage, and other parts functionality. When your phone is in trouble, the repair technician will likely do the so-called line checking or circuit tracing on the PCB. The procedure is quite common and standard to find out what kind of issue your phone has and what is the source of the issue.
In case you decide to do your own PCB repair, keep in mind that the PCB track is drawn inside the board, so it is basically invisible. The PCB isn’t a regular board as it connects parts to make sure that everything works in harmonious balance. The LCD, vibrator, speaker, mic, ringer, and others are depending on the track, so in case one line is interrupted or broken, it will definitely affect the corresponding part.
As it was mentioned before, finding out whether a line or a track is broken isn’t easy. If you want to trace them, you need a diagram to help you. Each product comes with its own specific diagram, so it is quite impossible to make mistakes in identifying which diagram belongs to which device.
If your Nokia C1 phone seems to have mic issue, you only need to type in Nokia C2 mic issue and solution in Google Image and your problem is solved. Different problems will have its different diagram, so consult the net to repair your device.
Use multimeter when checking the line. When it is beeping, then the line has no problem at all. But when there is no beeping sound, the line is definitely broken. Use a jumper wire and solder it to solve the issue. You may also have to check on other components or small parts.