Building trust every day  Rockwell Collins Museum

Mar-27 ···
233D Transmitter Restoration Project

Mike heated the High Voltage rectifier filament transformer and we were able to get the cover back on. I’m back to “cooking” 872As as I am working on other things. I’ve installed one of the “new” (1959 date code) 872As to replace the one that has lots of black flakes floating around.

We installed the “low” voltage power supply. Used 3B28s rather than 866As because the 3B28s were installed when we got the transmitter. Low voltage supply filaments come up as they should, but the plate supply relay in the power control comes on when the High Voltage button is pressed and Low Voltage tune is selected, but then goes off. May be necessary to complete the door/panel interlock circuit to get the relay to latch.

Started looking at the 175R-3 tone control chassis. The phone dial is fed from a pot across the filament supply and then goes through a couple of stages including a “dial pulsing” stage that uses a 6L6. There is a 60 cps “Acceptance” filter that goes in the dial pulsing circuit and a 150 to 4000 cps “Bandpass” filter, and a 3000 cps “Rejection” network. Mike input is on this chassis. No PTT!

We posted a list of 21 tasks that are considered essential to continue testing in the TX room. We’d like to get substantially all of these done by April 16th. We rotated one of the benches 90 degrees so we can have access to the white board in the room. We’ll use the board to provide information exchanges and status information. Or draw cartoons.