Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: drgonzonm on December 11, 2013, 02:39:18 pm
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Been on the forum almost two years and didn't see any reference to the above question.
For those afraid to ask, a not so important question. from: http://www.ampbooks.com/home/amp-technology/battery-amp (http://www.ampbooks.com/home/amp-technology/battery-amp)
In a typical radio built in 1925, the "A" battery supplied filament heat. This is where most power
consumption took place. The battery was physically large and created low voltage and high
current. It was usually a lead-acid battery charged every week by the automobile mechanic
down the street.
The "B" battery, on the other hand, supplied high voltage and low current to the plates and
screens. It lasted a lot longer but was expensive.
Finally the "C" battery set the DC grid voltage. There was never any need for an on-off switch
for this battery either, because grid current was extremely low while operating and non-existent
when the heaters were turned off. Thus the C battery was also left continuously connected.
Through the years it collected dust and cobwebs and eventually died of old age.
So lets not be C batteries
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i was wondering myself,thx for sharing with the class.
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A B and C batt connections.
Note multiple B-batt taps-- 130+V for power tube, 90V for driver, 45V for detector and RF stages.
C bias for a type'71 is 30 or 40 volts.
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Portable radios of the 30s through early 50s used the A, B, and maybe even a C in the battery pack.
People I worked with in avionics, referred to "B-plus" some times, and really didn't have a clue why it was called that !!
As a kid in the 30s & 40s, my dad showed me how to build one & two-tube radios....after I graduated from crystal sets :icon_biggrin:
Best, durable B battery was a bunch of D cells soldered in series......