[morzh]

The 20 pot has two sections: one is the Antenna attenuator, the other is the cathode bias one.

[dconant]

To clear things up a bit. The Philco pot (33-5040) is single gang 3 terminals with AC switch. The picture shows how my pot is wired and the description of the post from the Philco parts catalog. Note the 32K resistor on my drawing is not on the early or late schematic. Looks to me like someone has wired the pot trying to use both the early and late schematic.

[morzh]

Oops, sorry. I've answered a question no one asked.

[MrFixr55]

That's OK, Morzh, I do that all the time. If we could catalogue the answers to questions that no one asked, when they do ask them, the answer is there. It would be like we're clairvoyant!

[morzh]

Well, now you ask that question and there we are, the time travellers.

[MrFixr55]

Hi Dconant,

Yeah, I think someone tried to combine the 2 functions.  I don't think it will work.  In the early 27 schematic, the field coil and the 1K Ohm potentiometer's resistor is in series, across the B Supply, between B+ and Chassis ground, which represents B- and C+  the wiper goes to the cathodes of the 2 RF amp tubes.
 
For (somewhat) more clarity, I cut away the power supply from the rest of the schematic.
   

I think that to get this to function right, ensure that the Antenna coil and tuning cap are wired according to the schematic for the earlier model (Volume Control controls cathode bias only.  you may have to put a 2K resistor across the 2 "end" connections on the pot that are not the wiper contact.