Sorry I can't add much to this discussion, but it's way over my head. I spent some time checking the pin 5 voltage. With no connection to the audio source, we get 0 to -.8V.
When I plug in the earphone jack with the audio power off, we get -5V. With the power on, we get +5V. If I leave the meter on pin 5, the + or - 5V bleeds down, losing about 1V per minute. I put in a spare 117L7 and got the same results.
Tried tuning the coil with a 4-ft antenna set up 15 ft from the receiver, but received nothing at 900 KHz. I have a couple of table radios with loop antennas, but they're too noisy between stations. So, If the radio won't come to the transmitter, then the transmitter will go to the radio.
Alas, this didn't work either. We're being visited by our grandsons for the next couple of weeks, so I won't have much time to play with this. On the other hand, at 7 and 10 years old, they're both a lot smarter than me, so maybe they can figure it out.