When I got the A.R.C. Type 12 Radio Set working, I did not have a suitable dynamotor, let alone the correct one, a D-10A. Anxious to get it going for upcoming hearability experiments, I designed a simple solid state power supply that plugs into the 3 pin connector on the rear of the R-19 receiver in place of the dynamotor. In the A.R.C. Type 12 system, that dynamotor powers both the receiver and transmitter.
The mechanical mount needs to be reworked as this is really a circuit design prototype, but the power supply runs the receiver and transmitter quite well. It puts out the required +250 VDC with only 0.5 volts ripple with +13 VDC input. The oscillator frequency was set to be about 25 KHz to make the transformer and filter small and simple; it runs at 80% efficiency. That oscillation frequency is well above the bandwidth of the audio circuits (as well as my ears) so it is inaudible while running, either acoustically or electronically. Runs only slightly warm and not bad for a first attempt.
Above: Built in a minibox, using a balsa wood “connector” and three brass sleeves for contacts to the receiver dynamotor connector. Works well enough for circuit testing.
It will also run a Command Set receiver although the voltage is a bit high for those radios. I will build another one with about 220 VDC output for those. When I complete the design and testing I’ll place the schematic here. However, the key is the ferrite transformer and it uses a core that I had in my junk box – it may be hard to replicate with a different core (and material). I’ll try to find a suitable replacement from parts available these days and then evaluate a design based upon that. Stay tuned…