Bernina Minimatic 707 pedal/speed regulator gets very hot!!?

Hi,I have a Bernina Minimatic 707 from 1971. When I sew with it the pedal gets very very hot. It is too hot to touch and has even smoked. A Bernina dealer replaced the pedal for me but the new pedal gets extremely hot too. I burned my fingers on it. I don’t know if this happens only when I sew or if it happens just because it is plugged in. I always unplug it when not in use. I don’t have the machine at the moment otherwise I would test it. The rest of the machine works well and it was serviced recently . What could be the problem? How can I fix it?