Here's the solution for Nokia C1-01 Earpiece Speaker problem that has no audio Sound can b heard on it during a call is made. If this problem there is a possibility the earpiece speaker is already busted or damaged due to audio signal overdrive. Some factors are of dirty or oxidation build up on the earpiece terminal contact pads.
This solution below shows which particular components needs to be check for hardware repair troubleshooting.
Check the earpiece speaker first by using a multimeter set to X1, you can hear a crackling sound when hitting the two terminal with the tester's probes.
Clean the earpiece terminal contact pads on the C1-01 PCB board.
If the earpiece speaker is working and the contact pads is already cleaned but still the problem still exist. You may used the solution above and check those highlighted components, it is composed of filter coils, an ESD protection resistors and bypass capacitors.