Collins Aerospace Museum

233D Transmitter Restoration Project


Ready for assembly.

Many thanks to Nicole and our Fab Department for repainting the transformer case and power control cover.

When restoring museum artifacts it is especially nice to have the correct paint applied by in-house professionals.
Larry is the MVP again this week. Two more of those and 5 bucks should get you a cup of coffee almost anywhere. Attached is his power cart with the newly painted plate transformer enclosure. He is touching up the insulation on the wiring for the transformer and when he is satisfied, he will put the big iron back in the case. He also got the case for the power contactor nicely painted and as soon as Mike Hynek and I finish the contactor rewire, we can install it on the power cart.

It appears that the wiring issues on the power contactor were the result of changes made to allow the transmitter to used on single phase power. The “B” phase was not connected beyond the main breaker. Apparently there was no attempt to make the autotune system function. Would be interesting to know if this done while Western Airlines had the transmitter in service.

I noticed that the time meter in the power supply bay is showing just over 5000 hours. (Unless the final digit is “1” and not “0.1”). So it was likely only powered up when needed.

As I am reassembling the bias supply, I noticed that the “plate” transformer has a masking note saying that it was rewound in 1948. So did the original transformer get rewound in 1948 or was the original transformer fail and get replaced by the rewound one at some point after 1948? Since the Western Airlines drawings were dated 1950, I had always assumed they created before the transmitter was installed, but that may not be the case. Question remains whether this was the only 233D that was ever built or were there others? I have some feelers out to some folks who have an interest in Western Airlines history to see if they can fill the blanks, but most of them were more interested in airplanes that radios. I have a couple of old Air Force friends in Sacramento, but one is on a heart transplant list and the other has cancer, so neither has able offer any help.

Larry is looking for new wiring between the power cart and the transmitter. We decided that we will allow about 16 feet for the high voltage cable between the plate transformer and the HV rectifier. So we will need 64 feet for the four conductors. We expect that we will need another 35 feet or for the balance of the high voltage cabling in addition that already supplied by Rod. We are not sure we can buy anything less than a full spool and it is pretty pricey. We think it is likely 16 gauge wire but likely could use as small as 18 gauge. We look at real copper spark plug cable if we can’t locate any of the other stuff at a reasonable price. We also plan to replace all of the AC control wiring between the power bay and the power contactor. Some of the wiring goes through access holes in the bottom of the racks that are not fitted with grommets. We will use “centipede” strips for the larger holes. Some of the original rubber grommets in smaller holes appear to be in good condition, but we should change most of them.

We’re chipping away, but lots of work remains.

The leads to the primary windings, visible in this photo, have a couple of scuffed spots - so we’re painting them with liquid tape to avoid contact with the case.

The high voltage, secondary, leads are simply covered with an insulating sleeve - which are all in good condition.