Actually I tried a couple of other configurations which didn't work, but they were based on my lack of understanding of the antenna coupling transformer. So I'll disassemble the set tonight to see if I can find faults.
Now, looking closely at the coupling transformer, which I viewed as a single coil, like a choke, tapped in the middle for some mysterious reason. I see that at the antenna connection (red), there are two wires--one for an inner winding which ends at the yellow terminal and the second for an outer winding which ends at the black terminal. So there are effectively two coils which mysteriously act upon each other when the signal current is present. Does this work like a step-up transformer?
