[planigan]

Hi, I checked the schematics for Philco 20, 20A and 20-A on Nostalgia and they were all push-pull outputs which reguire center tapped primary in output transformer. So, there has to be four wires connected between set and Spkr/Field Coil. Each end of primary goes to a plate on an output tube (2 leads), the center tap and one end of Field Coil to B- (1 lead) and the other end of Field Coil to B+ (1 lead), making a total of 4 leads between chassis and speaker. Search around the transformer bottom at the paper edges for a cut/broken lead. If you find a stub you may be able to carefully peel it back enough to piggy tail a lead on to it and you have your third lead. By the way, I believe you said you have 300 ohms on primary of transformer. I did not note ohms of primary from schematic but that could be 1/2 the resistance or full if you are measuring from end to center tap or end to end respectively. PL