Looked at that schematic for a bit and it can drive you up the wall beyond a point, correct me if I am wrong but it looks like there are two RF stages followed by a mixer and separate HFO then two stages of IF and what I would suspect a grid leak detector in the final IF tube. The mind blowing part is the mixer tube also has a triode used as a audio driver that feeds a push pull audio output pair of triodes with one in each RF amplifier all transformer couppled, cannot explain the two remaining triodes in the first IF and HFO, one has to be a BFO oscillator but no clue witch and what the other is doing?