06-27-2014, 10:56 PM
Most people don't try to make these DC only sets operate from AC all all, they just sit them on a shelf an look at them, though I am sure that it is feasible to make one functional in it's original state. Since it was designed to operate from 110 volts DC you would need to operate the set from a 110 volt DC power supply, at least for the B+, that is without severely butchering the chassis. This is not to be confused with an AC/DC set, these radios do not have a rectifier tube or power supply built into them like an AC/DC set would have. If I remember correctly the tubes would be connected in series string, and would also use a line dropping resistor, much like an AC/DC set, but the B+ side would run directly off the 110 volt DC power line with maybe a filter cap to get rid of any noise.
I've never seen one of these sets in the flesh but I don't think they are all that common, the main market would have been limited to urban areas with DC power grids. One easily reversible mod that you could make would be to split the input to the 110 volt B+ line from the tube filament string, and bypass the ballast so you can run the tube filaments off of exactly whatever voltage they need.
It looks like the tubes in this set are all AC tunes with indirectly heated cathodes so you may be able to operate them off of AC, once the B+ circuitry is split off. The heater voltages end up totaling 87. 8 volts at 300 ma, you could build a DC power supply, with transformer, to run them but that's a bit on the heavy side, but something like a small isolation transformer may work. But if you are going to operate the tube heaters off of DC you might as well build a DC power supply with enough current capacity to supply the B+ as well.
One idea that may work is the diode trick, which drops the line voltage down to I think around 85 volts, then it would be DC but unfiltered DC, for that you could skip the power transformer. For the B+ you have no choice, you need a 110 volts DC, but for that you could build a transformerless power supply off board. So you have two options, run the set off of a higher current 110 volt DC power supply, with isolation, or go the cheap route, mod the set a little, and build a transformerless power supply for the tube heaters and the B+, with no isolation. I would try going with the former.
Regards
Arran
I've never seen one of these sets in the flesh but I don't think they are all that common, the main market would have been limited to urban areas with DC power grids. One easily reversible mod that you could make would be to split the input to the 110 volt B+ line from the tube filament string, and bypass the ballast so you can run the tube filaments off of exactly whatever voltage they need.
It looks like the tubes in this set are all AC tunes with indirectly heated cathodes so you may be able to operate them off of AC, once the B+ circuitry is split off. The heater voltages end up totaling 87. 8 volts at 300 ma, you could build a DC power supply, with transformer, to run them but that's a bit on the heavy side, but something like a small isolation transformer may work. But if you are going to operate the tube heaters off of DC you might as well build a DC power supply with enough current capacity to supply the B+ as well.
One idea that may work is the diode trick, which drops the line voltage down to I think around 85 volts, then it would be DC but unfiltered DC, for that you could skip the power transformer. For the B+ you have no choice, you need a 110 volts DC, but for that you could build a transformerless power supply off board. So you have two options, run the set off of a higher current 110 volt DC power supply, with isolation, or go the cheap route, mod the set a little, and build a transformerless power supply for the tube heaters and the B+, with no isolation. I would try going with the former.
Regards
Arran
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