[R-390] in rush current limiters

[ToddRoberts2001@aol.com]

In a message dated 12/23/2002 12:05:46 AM Eastern Standard Time, 
vze2gmp4@verizon.net writes:


> If tubes are connected in series  and equal voltage drops are required for
> tube performance then shunt series regulation is called for.  That's why
> the ballast tube is there, it's not just there to drop 12 volts, or
> because the navy had crummy generators on board ship.  Same can be
> accomplished with a current  regulator or constant current source.  It's
> good design practice.  The better receiver's of the past that had some
> tubes in series have ballast tubes going back to the 1930's.
> Try it.  Measure the voltage drop on a 390a with it's ballast tube in
> place and you'll find they're quite equal.
> 
> If the above statement you made came from a book, throw it away and get a
> good one.                                                                   
>                                                     The last time I looked 
at ohms law,  E=IxR.  Unless the hot resistance of each filament in series is 
exactly the same, unequal heating can occur. I guess some people don't 
remember ohms law. 73 Todd Roberts WD4NGG.


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