|[AMRadio] WTB/WTS and a question|
Brian K Harris
brian.k.harris at philips.com
Fri Dec 30 11:21:15 EST 2005
1. I would like to buy or swap for two solid state plug-in replacements
for the 872A mercury vapor rectifiers for my KW-1. Enuf said.
2. I am restoring a broadcast/shortwave radio set for my brother. It is
an RCA 8BT, battery operated 'farm set' from the 30's. In addition to
using three 45V batteries in series for the 135V B+, it used four small
1.5V cells for biasing the 1st detector and the 1st and 2nd IF's, and a
multi-tapped battery to get 3V bias for the 2nd detector and 7.5V bias for
the audio driver. As my brother doesn't live on an electricity deprived
farm, I am building a solid state AC supply to meet those needs.
The tubes all have 2V filaments. The radio has two inputs for a filament
supply, 2V or 2.5V (the 2.5V input merely inserts a series resistor). My
question is....why did anyone manufacture 2V filament tubes and what kind
of battery put out 2V or 2.5V? I am building a solid state supply for the
2V requirement as well so the question is merely to satisfy my curiosity.
By the way, this set uses a pair of push-pull 49's for the audio output
stage. These are zero bias tubes in Class B with 3.5W capability. Very
Thanks for reading,
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