GM Gents
Your comments are much appreciated. I will attempt to answer all questions in a single response.
Dynamotor rebuild: Yes, I rebuilt it when I put the dynamotor into service about 10 years ago.
All caps were replaced in the BC-456 modulator.
Float Power Supply:
This is what I'm using now, and it's not working out well. I measure 26.8V power off.
Power On Key Up: 23.8V Power On Key Down: 23.5V. This gives me an Ep of only 480V.
The above voltages are measured directly on the battery terminals.
New Power Supply:
Wire Sizes: This could be an issue and I realized it early on. I'm using 18 AWG doubled up.
That means each connection uses two wires in parallel.
Not optimal, but a single 18 AWG wire wouldn't do.
Changing to a larger wire size isn't a problem (I just have to get some).
The dynamotor is spec'd at 5.8 A @ 28VDC so I figured paralleled 18 gauge wire should work.
28-0-28V 50A. Using a full wave bridge rectifier. Positive lead goes to 0.5 ohm resistor for current inrush.
That's connected to a 20,000 uF filter capacitor. Using a 680 ohm 2W bleeder resistor.
I would prefer to use a 1 ohm, but didn't have one of sufficient wattage.
Using a IM-11 VTVM for all the following measurements (unless otherwise indicated)
I have panel meters for voltage and current in circuit -- voltages agree with VTVM readings.
With the Panel Meter set for 28 VDC:
Voltages / current measured at the filter capacitor terminals:
Key up: 28V 4A
Key Down: 24V 7.5 A. 510V Ep 30W output
Voltages measured at the bridge rectifier output:
Key up: 29 V DC
Key Down: 26 VDC
Voltages measured at the transformer output (using DMM)
Key up: 28.34 VAC
Key Down: 27.41 VAC
If I increase the voltage to 30 VDC measured at the filter capacitor output:
Key up: 30V 4A
Key Down: 25V 7.5A Ep 550V (which is what it should be) 40W output
Current spike on startup: Yup it is !! As expected.
73 Mark K3MSB