Usually the transformer is not in the chime box, but somewhere else. Where is the sound coming from?

Sounds like you may have a short in the circuit somewhere. For example a button that is bad will activate the chime all the time and make a humming noise. Try to disconnect the button and see if that fixes it. If it doesn't you probably have a short in the wire somewhare and you may need a professional to find it for you. Mr. Electric