Building trust every day  Rockwell Collins Museum

Aug-11 ···
233D Transmitter Restoration Project

One small step, but a giant leap for our side today!

We pulled the exciter (with some work on our “fixture” we’ll be able to do it with ease).

Jules and I pulled off the Autotune box chassis after considerable discussion about how to keep everything timed properly. Turned out to be fairly easy although there will be some things that we have to use some care when we reassemble. Good new is that we discovered the source of our binding problem with the exciter tuning assembly. The slip clutch assembly has four screws holding a cover on and one of the screws had back out several turns and was describing an arc in the paint on the back wall of the box. It is doubtful this is the source of our oscillator problems, but certainly would prevent proper tuneup. The plate tuning Autotune on the PA output network was also binding when we last used the system, so we will pull the casting off to see if a similar problem exists there. We should also check the grid network for similar problems. Now that we’ve learned how the boxes come apart, should be no problem. Jules has some images that I will forward as soon as he sends them.

I have a couple of Heathkit SB series supplies that provide 800, 300 and bias voltages. I’m going to use one to power up the 837 and 807 on the bench to let us to better access to the oscillator circuit. We can power the filaments and keying bias supply from the single phase 208 available in the room. I intend to keep the exciter out of the rack until we get the oscillator/multiplier stages going.

Goal is RF by Labor Day! (at least out of the 807; 813s may take a little longer.)