[mikethedruid]

I looked more closely at that tone control when I pulled it to clean it. I would swear it is something original, were it not that I have not seen that mentioned in the revisions. Do any of our Philco experts know if the factory ever used a 1 MEG pot in this position, connected so it went between where condensers 40 and 41 meet at one terminal of the switch type control, and ground, the other connection of the control ?
http://www.nostalgiaair.org/Resources/208/M0013208.htm
(the schematics for reference)
It looks like it may be a very workable circuit. I'll be interested to see. It seems to be an audio taper pot.