[AMRadio] WTB/WTS and a question


Bob Macklin macklinbob at msn.com
Fri Dec 30 12:01:01 EST 2005


A single wet cell (lead/acid) battery produced 2.2V.

Bob Macklin
K5MYJ
Seattle, Wa.

----- Original Message ----- 
From: "Brian K Harris" <brian.k.harris at philips.com>
To: <boatanchors at theporch.com>; <baswaplist at foothill.net>;
<amradio at mailman.qth.net>
Sent: Friday, December 30, 2005 8:21 AM
Subject: [AMRadio] WTB/WTS and a question


> 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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