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  • How to fix a classic American AM tabletop tube radio

    oops--A is for filaments or heaters, low voltage typ 1.5V to 6V, usually able to supply more current than the other sections; B is the plate supply much higher voltage than A, typ 22.5 to 135V; C is the negative grid bias usually 1.5 to 15V doesn't need to supply much (if any) current.The newest radios I can think of that use A,B,(C?) batteries are the pre-solid state Zenith Trans Oceanic models. ISR the batteries were built into a single block integrating A,B, and C together. As far as exchanging A and B batteries-- some tube-type hearing aids had the same shape and size separate A (1.5V) and B (15 or 22.5V) batteries. Needless to say, ignoring the warnings and exchanging these batteries causes the normally almost invisible filaments to light up brightly, but only for a few seconds, b...see more »oops--A is for filaments or heaters, low voltage typ 1.5V to 6V, usually able to supply more current than the other sections; B is the plate supply much higher voltage than A, typ 22.5 to 135V; C is the negative grid bias usually 1.5 to 15V doesn't need to supply much (if any) current.The newest radios I can think of that use A,B,(C?) batteries are the pre-solid state Zenith Trans Oceanic models. ISR the batteries were built into a single block integrating A,B, and C together. As far as exchanging A and B batteries-- some tube-type hearing aids had the same shape and size separate A (1.5V) and B (15 or 22.5V) batteries. Needless to say, ignoring the warnings and exchanging these batteries causes the normally almost invisible filaments to light up brightly, but only for a few seconds, before burning out. Batteries from these old days were made from series connected multiples of 1.5V cells-- look inside a 9V battery for a contemporary example. You will find either stack shaped cells, or one or two brands use tiny quad-A (AAAA) cells.

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