@modjo, Laurentiu, Saulail, open the microphone and control buttons case on a set of earbuds/ear phones. The case will probably either snap open using a blunt thin blade(guitar pick) prying at the seam or if molded/glued, you will have to very carefully(not to damage board or controls) use a sharp blade/razor knife to cut open along the molded seam. This will gain access to see if wires broke from board,etc. Links below to show the 2 methods. Good luck.
I hope this helped you out, if so let me know by pressing the helpful button.
[guide|10501]
https://www.youtube.com/watch?v=-w6K6kDK9Kw