[MrFixr55]

Hy Myrute, 

Welcome to the Phorum!

I am not sure what connections go where on the transformer because my Model 20 did not have the "Pie Plate" speaker.  

I have attached 2 drawings, one a drawing of the speaker jack from the outside chassis rear apron view.  The other is the schematic.

The Model 20 was a game changer for Philco, starting the "Cathedral" radio craze and rocketing Philco to one of the largest (if not the largest) manufacturers of radios.  For a "low priced" radio, the Philco had 2 stages of "screen grid" RF amplification, a "biased" detector (better fidelity than the grid leak style detector), 1 stage of audio amplification and a Push Pull Audio Output for more power and better fidelity.

This speaker does not have the "Hum Bucking" coils that later electrodynamic speakers have. If hum is excessive, reverse the 2 connections to the field coil.

Search the Philco library for a great Ron Ramirez article on a circuit mod for the audio interstage transformer that improves fidelity and helps prevent burnout by capacitively couples the transformer to the plate of the first audio stage.

IMHO, the speaker is the only weak link to this radio.

Good Luck with this winner of a radio.