[GreenKeys] tube?

[Bruce Gentry]

On 1/6/13 3:01 PM, 73131.3073 at compuserve.com wrote:
> Does anyone know what tube was used in some Model 31s? Looking at the 
> diagram of the 31  dynamotor is soooo interesting! The tube that 
> regulated the dynamotor is also excited by the same dynamotor! How 
> about that for feedback! I hope the tube had a filament that warmed up 
> fast!
> By the way, there are several pictures and a brief writeup of the 
> Model 31 in the little book 'HAM-RTTY' published in 1963 by 73 Inc. on 
> pages 34 and 35.
> 73,
> Tim Swarthout, WA5QEG
>
>
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I have not seen the diagram, but there were several special diode tubes 
designed for use as regulators used in the late 1940s and through the 
50s.  They usually had a pure tungsten filament  and were designed to 
drastically change  emission with a small change in filament current and 
heating.  Most circuits sent the voltage to be controlled through a 
variable resistance to the filament, and current drawn through the plate 
circuit would reduce output of the device being  regulated.  It was 
simple, robust, and had enough damping in the response to handle sudden 
load changes better than many other methods  at a fraction of the cost 
and complexity.

     Bruce Gentry,  KA2IVY
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