[Arran]

Like with Mike I have also run into the experience of an error in the diagram, though I can't remember in which radio, I think it was with a part value like a capacitor where they put the decimal in the wrong place, or a resistor where they left out a zero. I have also run into a factory wiring error, most recently in a Phonola radio from 1937, they tied the wrong two pins together on the 6K7 IF amplifier tube, the suppressor grid to chassis ground through the tube shield pin, it was supposed to be connected to the cathode and it is in most sets. This may explain why there was evidence of the set being in and out of the service shop until the 1970s when it was retired, and why the IF amplifier tube was a more recent replacement, suppressor grid being more negative then the cathode probably did not help the performance of the set, or tube life. Someone on the assembly line in 1937 got clockwise and counter clockwise mixed up, pin 8 and pin 1, pin 8 is the cathode, pin 1 is the tube shield.
 Here is a diagram of a similar set, the main difference is that the one I was working with had a magic eye tube, so maybe it was a 772-S. 

https://pacifictv.ca/schematics/phonola762sdata.pdf 

Regards
Arran