As a follow-up, the utility company was of no help, and advised I call an electrician. I elected to get a Furman power conditioner, because they advertised their ability to compensate for low voltage and deliver voltage within the appropriate range. I installed the unit and it worked as claimed, but it also showed the available voltage at 115V, instead of the 106V or 108V tha the Panamax was showing. I'm now wondering if the Panamax, which is at least 25 years old, was the culprit. In any event, the problem appears to be solved.