[Arran]

I don't know if this is related to your problem but you missed one capacitor, there is a two section wax dipped mica capacitor at one end of the pushbutton coil assembly that can go bad apparently. Other then this I would go back and check the wiring, make sure that it matches the schematic for the correct code number and production run (aside from the 5Y3 mod). The audio output transformer should normally have B+ going to the center tap of the primary, and from that center tap to the screen grid of one of the #41 output tubes and throught a 3900 ohm resistor to the screen grid of the other #41 tube. The two outside legs of that transformer going to the plates of the #41 output tubes, one side of the secondary should go to chassis ground or common negative.
Regards
Arran