Power Supply for a 1920's Radio
by Chad Hauris
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These radios actually require two battery supplies...one for the tube plates (this is called the B supply) and one for the filaments (this is the A supply). Sometimes a negative bias supply (the C supply) is needed.
1920's Sorber radio with Atwater Kent Speaker .
In the 20's, the Model T Ford battery or other such storage battery would have provided the 6-volt A supply for the filaments. The filament current draw is around 1.25 amps. The B supply would have come from large dry-cell non-rechargeable batteries. As the current draw for the tube plates is fairly low (around 15 milliamperes) this battery would have lasted a long time.
So, we needed to construct a fairly high-current, low voltage supply for the filaments, and a higher voltage supply (at 90 and 22.5 volts) for the plates.
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