[Mr. Carlson] bought a Globe Scout Model 40A ham radio transmitter at a hamfest. The 40A was a grand old transmitter full of tubes, high voltage, and a giant transformer. It is really interesting to see how much things have changed over the years. The transmitter is huge but has comparatively few parts. You needed a crystal for the frequency you wanted to talk. There were two little modules that were precursors to hybrid circuits (which were precursors to ICs) that were often called PECs or couplates (not couplets) but other than those, it is all tubes and discrete components beautifully wired point-to-point.
The really surprising part, though, is the back panel. There’s a screw terminal to drive the coil of an external coaxial relay that has line voltage on it. There’s also a plug on the back with exposed terminals that has plate voltage on it which is considerable. In the 1950s, you assumed people operating equipment like this would be careful not to touch exposed high voltage.
[Mr Carlson] does a great job of walking through the schematic and, of course, also fires the radio up and looks at the output with a communication monitor. It has been a long time since we’ve loaded up a tube transmitter and watching it done while looking at the output was very nostalgic.