[MrFixr55]

Hi PeteLeoni,

Per the Philco service documents, the green and white wires are the 2 legs of the transformer primary.  These go to the plates of the 42s.  The green/white wire is common to the output transformer center tap and the field coil.  This wire connects to the junction of filter choke #85 and 8.0uF cap #88, the output of the rectifier and filter.  The final wire, blue, is the output of the field coil and connects to the junction of 2.0uF cap #62B and 7.750 Ohm resistor #77.  This is the B+ supply to the rest of the radio.

Ignore the color dots for now; they were not placed there by Philco, and may not accurately represent the modern color coding that Rod describes.  Since the colors of the wiring are quite faded, you can do the following:

• Ohm between the 2 wires on the right side of your speaker.  The reading should be about 1400 Ohm.  If so, this is the field coil and the darker wire is the "Blue - White" wire described in the schematic.  The other lighter color wire is common to the center tap of the transformer and the field coil.  
  
• Ohm between that "common" wire and each of the other 2 wires.  You should get readings that are approximately equal (there can be a 50 - 100 ohm difference.  These are the "legs" of the output transformer that connect to the plates of the 42s.  BTW, I don't think that the resistance value for the output transformer primary stated in the schematic (5300 Ohms) is accurate.  That may be the impedance but it is not the resistance.
  

Hope this helps.