Collins Aerospace Museum

233D Transmitter Restoration Project

I roughly set up the dial tone levels on the tone control chassis and am getting fairly reliable Autotune activity on the exciter chassis assembly. On three of the channels, I’m getting good repeatability with regard to the band and tune Autotunes returning to the same settings. On the other channels, the band switch returns to the same spot, but the tune control varies somewhat. I expect the likely cause may be the worn condition of the U-joints and couplers. Jules think he can get the new parts in a week or so and then we will need to get some machine work done on those parts as well as get the shafts made for the grid and output network.

I am also getting “turn off”and “turn on” commands when I dial the appropriate sequences. This is encouraging because it means that the tone control assembly is sending the proper signals to the rest of the system and the Telco assembly is decoding properly.

We are still not able to get the keying signal to the exciter. Mike is still working on tracing the circuits to define the undocumented mods. We have built a break out box for the keying relay, so we can install that and attempt to force keying.

Rod and I have been looking at ways to provide the 9 dB attenuation we need to reduce the carrier from 3KW to 375 watts to allow us to legally operate on ham frequencies. We think we should operate at rated power to keep everything happy. The 9 dB loss will also reduce harmonics and spurs, so that should be a positive. Fun project!