In article . net,
"COLIN LAMB" wrote:

I think the DM-32A was the designated dynamotor for the BC-453. The design
output was 250 volts at .05 amps with 28 volts input. In conversions, the
DM-32 could be used for powering it, as it had 12 volts input and the same
output.

Colin-

Back in the 50s I used a low frequency ARC-5 receiver (BC-453?) to tune
the 455 KHz IF of a National SW-54, making it a double-conversion
receiver.

The dynamotor had a 28 volt field winding that consisted of two sections
in series. It was common to reconnect them in parallel, and operate off
of 12 volts. However, that produced half the HV output. If there was
more to the mod that gave the full 250 Volts, I never came across it.

Fred
K4DII

On May 17, 4:48 pm, Fred McKenzie wrote:
In article . net,
"COLIN LAMB" wrote:

I think the DM-32A was the designated dynamotor for the BC-453. The design
output was 250 volts at .05 amps with 28 volts input. In conversions, the
DM-32 could be used for powering it, as it had 12 volts input and the same
output.

Colin-

Back in the 50s I used a low frequency ARC-5 receiver (BC-453?) to tune
the 455 KHz IF of a National SW-54, making it a double-conversion
receiver.

The dynamotor had a 28 volt field winding that consisted of two sections
in series. It was common to reconnect them in parallel, and operate off
of 12 volts. However, that produced half the HV output. If there was
more to the mod that gave the full 250 Volts, I never came across it.

Fred
K4DII

Back around 1948, in the UK I recall buying a transformer that had 24
volt heater winding instead of 6.3, along with 5 volts for a rectifier
heater and centre tapped B+ 250-0-250 winding, specifically for war
surplus receiver power supplies. The input was of course 230 volts at
50 cycles. At around age 14 I built a such a power , supply but used
selenium rectifiers instead of a 5 volt tube.

It's just occurred that one could, and people probably have done so
many times already, use any conventional power transformer? Rewiring
the war surplus tube heaters from 24/28 volt to 12 volts, i.e all in
parallel. Then connecting them to the 6.3 + 5 = 11.3 volts windings in
series. An ARC 5, for example, has six 12 volt 0.15 amp tubes; 6 x
0.15 = 0.9 amps, well within the ampacity of both heater windings.
Then using SS diodes for the B+ which even at 250 volts was a maximum
of 60 m/a.

Taking all the wattage into consideration, even at 80% efficiency, the
consumption and heat dissipation would only be 25 watts or less?