The problem with the modulator is solved now. It was a bad connection in the chain of resistors
that returns pin 1 of the 6SN7 to ground. Because this grid was floating, with an old tube, it
would oscillate, sometimes, but poorly. I also checked all the precision parts in the circuit
under voltage stress. The were all ok voltage wise, and although out of spec from the 1 %,
decided to leave them in. A proper restoration would need stripping both terminals board in the modulator.
This would destroy the glass Sylvania 1N34s.
Next to do is dive into the oscillator case and see if a new 6C4 will allow full carrier set to work at 50 mHz.
The manual (on line) has full details on using the 1001A with test loops to measure the sensitivity of
radios. That would be great to see if all good transistor radios work the same way.
This is the modulator.
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