[AMRadio] WTB/WTS and a question


Edward B Richards zuu6k at juno.com
Fri Dec 30 12:09:20 EST 2005


Hi Brian;

In my ignorance, I have never heard of 2 volt tubes. What are their
numbers? Thanks and HNY.

73, Ed Richards K6UUZ
Simi Valley, Ca 93065
Home of the Air Force 1 pavilion

On Fri, 30 Dec 2005 10:21:15 -0600 Brian K Harris
<brian.k.harris at philips.com> writes:
> Good Morning,
> 
> 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 
> cool.
> 
> Thanks for reading,
> 
> Brian WA5UEK
> 
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