I have an A810 which seems to be at a constant high speed. I have no PPL light. It flashes occasionally, but never syncs and stays on. I've removed the board and mounted it externally and extended the TAC and motor wires, so I can look at the signals on an O-Scope. It doesn't appear to have anything on the TAC lines. At first I was getting what looked like a decaying ringing, but when I turned off the machine and unplugged it was still there. I'm thinking I'm picking up spurious AC or signal from a ballast transformer. What should the signal look like at the TAC input of the Capstan Control Board?