Electricians please: Two issues, on a ceiling fan the remote receiver circuit board is fried?

on the same circuit a potentiometer that controls the light "dimness" is fried. What would cause both the circuit board on the ceiling fan receiver to fry(i opened it, it is literally black inside) and the control dimmer to fry. An "electrician" sent his helper over to wire the house and I want to know what he might have done wrong.