Building trust every day  Rockwell Collins Museum

Apr-29 ···
233D Transmitter Restoration Project

Took in two more 3B28s and added a plate primary switch to allow the filaments to warm before the power is applied. Now voltage out is up to 660 volts. Let it run for about a half hour and it seems to be in good shape. So everything with the LV supply seems to be working with no problems. Just some cleanup.

Applied power to filament circuit on the Speech amplifier and all of the tube filaments appear to be working.

Need to add in a temporary bleeder resistor in the audio power supply and will check that out next.

After that, only the bias supply and the filament circuits on the exciter chassis need to be checked, except for the big plate transformer. We need to talk about testing the plate transformer.

Little problem with the phone relay assembly. The schematic we have is for the phone version of the assembly and it turns out we have the CW relay assembly. Haven’t been able to find a schematic for the version that we have. Only difference appears to be that the phone version has four 83 rectifier tubes and our unit doesn’t have the tubes and the associated transformer. I expect when system wiring is traced, we’ll find the source for the required power.

Measured to replace the missing glass in the modulator and power bay doors. We are missing three metal strips that used as retainers to hold the glass. Should be simple to fab. Discovered that the modulator bay door is bent to the point that it will to be straightened before we can replace the glass.

The punch list keeps growing, but I think we are making progress.