If anyone has wanted to add 425 Hz or 850 Hz shifts to their TU-300 or Heathkit HD-3030, or wants a spare active filter board for their TU-470, TU-300, TU-170A, or Heathkit HD-3030, I have the solution. I wanted a fully populated HD-3030, so just for fun, made a KiCAD project to duplicate the Flesher board. The result is a nearly exact replica of the Flesher board. If anyone wants one or two, let me know. Or, you can order a batch from PCBWay.