[R-390] in rush current limiters

[Jim Shorney]

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On Sun, 22 Dec 2002 16:03:01 -0800, Bill Smith wrote:

>The current is 300 ma.  AC.  It is simply the filament current of two 6-volt
>miniature tubes (v508-6BA6/5749, V701-6BA6/5749) in series.  The source
>voltage is about 25 volts.  12 volts is taken by the two tubes in series,
>and the ballast and decoupling inductors
>drop the other 13 volts.


Thanks for the info.  This makes the comment about using a diode
somewhat puzzling.  ISTM that a diode is going to half-wave rectify the
AC filament voltage and change the whole game about what exactly '300
mA' is.  Which would start another never-ending thread, no doubt.


>The idea is to build a 9-pin miniature tube plug-in replacement with no
>modification to the R-390A.  Only two wires are fed to the ballast socket.
>Ground is not available unless obtained by a tertiary wire or the socket
>shield. 


A three-terminal regulator configured as a constant current source
would not need a ground connection.  Just a heatsink.



- --
Jim Shorney      -->.<--Put complaints in this box
jshorney@inebraska.com
nu0c@amsat.org
Ham Radio NU0C
Lincoln, NE, USA
EN10PT
http://incolor.inetnebr.com/jshorney/
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