Collins Aerospace Museum

Jan 28
233D Transmitter Restoration Project

Some progress this week. No RF yet, but we are getting there!

We pulled the exciter to determine why the Autotune system was not working properly on Channel 9 and to determine why the oscillator/driver bias and keying system was not working. Jules is checking continuity to make sure the Telco chassis is getting the channel select signal from the exciter. Not a major problem since it appears that we are always getting the proper signal on lower channels. But we need to run it down.

The 230 volt tap on the bias supply transformer appear to be open. It appears that when the mod to replace the keyer tube with a relay was done, some of the primary wiring was changed. As wired, 208 was applied to the 230 and 220 taps. The fuse blew and apparently opened both of those taps. I had expected the primary would be open, but it appears that the 210 and 240 taps are still showing a reasonable connection to the “common” tap. I attached the primary to the taps for 240 input and will probably hook up single phase before we put the exciter back in the rack. If the transformer is bad, we’ll need to either find a replacement or “re-purpose” one of the other bias supplies.

Don Grimm brought in the other shafts/couplers and they really look good. He has a problem with the coupling into the exciter. The hole for the drive pin was not centered properly and his drive tool will not extract the old pin. He is planning to rework the tool so the pin will get extracted properly. If that doesn’t work, he’ll take the exciter to his shop to fix it.

Mike is building a breakout fixture for the Tone control chassis, so we can monitor critical audio and tone signals.