Did the cable break or is it just bound up? If it’s bound up, the process is to remove it, hang it up from the ceiling and pour Kroil penetrating oil into it, until it’s leaking out the bottom. Let it stay there for several days before reinstalling.
Also, regular checking of the elevator trim prior to each flight will also help keep it unbinding. During run-up I will adjust the trim all the way nose down, and then turn until you get neutral or take-off position (trim tabs should be parallel to the elevator).