12-07-2021, 11:54 AM
Looks like the 7 pin socket might have been for an external crystal calibrator. There is no way that a tube plugged in to that socket. Perhaps a previous owner built a separate calibrator box and connected it by a cable to the 7 pin socket.
It appears the socket provided 6.3V and B+ for the calibrator along with a connection to the antenna circuit and provision for the switch to turn it on and off. That's exactly what would be needed to connect an external calibrator.
It appears the socket provided 6.3V and B+ for the calibrator along with a connection to the antenna circuit and provision for the switch to turn it on and off. That's exactly what would be needed to connect an external calibrator.
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
