Well, the majority of pedal harps don’t have sound equipment built into them. Those that do seem to all take some very different approaches so it would probably be helpful if you were more specific about what make and model of harp you are curious about.
Although I never did any repair on electronics in a pedal harp my electric Camac lever harp uses the same basic system as their pedal harps and I have done some work on it in the past.