[Arran]

Some sets have a disconnect built into the speaker plug, but I don't think the 40-180 has one of those, it uses a Bakelite socket on the end of the speaker cable, so the output of the rectifier is connected directly to the input filter cap with the speaker removed. The typical old radio power transformer has a 350-0-350 layout on the high voltage winding, since these sets use an #84 tube as a rectifier the plate voltage is lower then most, I think 270 volts, and the rectifier tube shares the same winding as the rest of the tube heaters.
Regards
Arran