My DeWalt band saw does not turn on. The switch is okay and I have power to the "controller". I assume the controller is the variable speed control that is connected to the external rotary switch. On the assumption that the controller is bad, do I need to purchase the whole unit or are there serviceable parts? The controller is $137 so I'm looking for alternatives. Is this a common problem with this tool? The tool has been used minimally and shows little sign of wear.