[MrFixr55]

If there are RF suppression caps across the transformer or to ground, take them out of the circuit. A really leaky or shorting cap can do this. Alternately, connect directly to the power transformer primary with everything else out of the circuit (power cord, switch, rectifier and all other tubes removed.

This was a somewhat slightly more "deluxe" version of the 4 tube Model 80 loss leader, with 77 pentodes for 1st and 2nd detectors instead of the 36 tetrodes used by the original 80. This radio also received "police" band.

20K Ohm is likely correct, or maybe it should actually be lower! This is not the usual 500K "pot" (potentiometer) between the 1st and 2nd audio stages. The pot is essentially between Antenna and Ground and varies the strength of the signal fed to the input transformer. This is common on many early sets without AVC and that employed grid leak detectors or biased "power" detectors, including the Radiola 16, 17 and 18. Other sets like the Radiola 60 used the pot to either bias the RF and IF stage. Other sets of this vintage varied the antenna signal and varied the RF and IF bias.

This radio employs 6V tubes so any transformer from a 5 tube set that you can pull out of the junkbox with 6V and 5V windings along with the HV windings could work. I say 5 tube (if not an early Philco) because a 42 or 6F6 draws about twice the heater current that a 41, 6K6 or 6V6 draws. Of course, mounting it could be fun.