Last night we shut down our system main 120vac control panel, Main 480 vac motor start bank and local 120 vac operator panel. We have two transducers that are powered by a 24vdc power supply that gets it power from the main 120vac panel. These tranducers have indicator lights that will work with either ac or dc voltage. With all the power off the indicator lights stayed on. Our 3rd shift elect. Staff check voltage at a juction box to find that we had (with everything off) 90 vdc. What am I missing?