I have over 60 vintage sewing machines. Many of them have resistance wire foot controllers. I have had two of them break a resistance wire and no short circuit resulted. Only a great reduction in speed, or a dead spot. I've also never seen a vintage machine with a grounded cord. Only two wire plugs. As far as I can see, as long as the wires are in good condition there is no need to "update" anything to so called modern standards. Joe