[Amps] Not the Diacrode

[Ron Youvan]

>  The ramping is a lot easier to do 
> with DC supply than AC (which might use variacs, saturable reactors, or 
> other ancient technologies). I use an SCR regulated mains supply with 
> good filtering.

   Filaments can just as easily be ramped up on ac, this way with no 
fuss.  I have seen ferro-resonant regulator feeding the filament 
transformer, the size was carefully chosen so the low resistance of the 
cold filament "bogged down" the regulator to a few % out, as the heater 
warmed, the resistance rose as did the output of the regulator until 
opium temperature, current and solid regulation were achieved.
   I first saw this on 8.5 Volt 25 Amp Varian klystrons.
-- 
    Ron  KA4INM - The problem with socialism is that eventually you run 
out of other people's money.
                  [Margaret Thatcher]