Collins Aerospace Museum

233D Transmitter Restoration Project

Parts & Task Lists
Jim is removing and replacing the aged, and probably very leaky, high-voltage conductors.
Attached are a list of parts known to be needed for the restoration and a task list.

I’ll get the glass door panels and retainer strips locally. Rod thinks the 2000 pf, 10 KV micas were likely used on older broadcast transmitters; if none is available, we will attempt to “rebuild” the existing caps.

The large wirewound resistors are not too critical with regard to value except for the voltmeter multiplier. Likely could accept 20% higher resistance values.

Filter choke on the audio power supply appears to be open. Unlikely we can find an exact replacement.

Suggest we buy spare 872As if we can find new tubes at a reasonable price ($10 each).

Task list pretty general; anyone wants additional details, contact me.


Needed Parts:
1. 1 ea 300 pf 3KV transmit mica capacitor (condenser)
2. 2 ea 2000 pf 10KV (Cornell Dublier Type 50) mica capacitors
3. 2 ea glass panes 17 & 7/16 X 8 & 15/16 X 3/32 Thick
4. 4 ea 30K 5% 80W WW resistors (HV bleeder)
5. 1 ea 51K 5% 80W WW resistors (Intermediate bleeder)
6. 1 ea 50K 1% 50W WW resistor (Voltmeter multiplier)
7. 1 ea 30K 5% 50W WW resistor (Audio Power Supply)
8. 1 ea Filter choke, 6 HY, 200 ma, 85 ohms (Audio Power Supply)
9. 2 ea 872A rectifier tubes (spares for HV rectifier)

Major Tasks:
1. Fab Autotune Shaft
2. Re-plate Modulator final tube, HV Rectifier and Bias supply Chassis
3. 230V 3-Phase wiring
4. Mod bay rail damage
5. Mod bay end-panel damage
6. Repair Modulator Bay front door
7. St. James Gray clean/touch up
8. Replace missing glass in power and modulator bay doors/Fab three retainers strips
9. Inspect and repair system wiring
10. System interconnect drawing
11. Research history
12. Troubleshoot Audio Power supply
13. Investigate keyer circuit on exciter chassis
14. Test plate and modulation transformer