[MrFixr55]

GE did a similar thing on several AA5 radios including Models 547 and 574. The wiper of the pot was tied to the input of the AF amp, but there was a center tap to the pot that was connected to B-. One end leg of the pot went to the radio, the other to the phono. This was a single pot as opposed to the dual pot used by Philco. Center was min volume for both radio and phone. Thirn CCW for Phone, turn CW for radio. A lot simpler than the Philco method.