[R-390] A few SP-600 questions

[Joe Foley]

Hi Jim,

Have you mentioned your concern to Bill?  Seems to me
he would have considered that and taken steps, of some
kind, to remedy same.

Joe



--- "James A. (Andy) Moorer"
<jamminpower at earthlink.net> wrote:
> I generally agree, but there is one mod suggested by
> Kleronomos that should
> be avoided. He suggests putting in a current
> regulator in the filament
> supply for the RF desk. The idea is to stabalize the
> power to the VFO tube
> filament to improve frequency stability. That is a
> laudable goal, but doing
> it with a current regulator to a bunch of tubes that
> are wired in parallel
> is asking for trouble. If one of the tubes filaments
> goes open, the current
> regulator will pump 4 tubes worth of filament
> current into the remaining 3
> tubes. The voltage across the filaments will go up
> accordingly. Bad idea.
> Kiss off four tubes just because one died.
> 
> If you want to regulate the filament of the VFO, you
> should put in a voltage
> regulator - not a current regulator. Unless, of
> course, you also plan to
> rewire the filaments so they are no longer in
> parallel.
> 
> The reason the ballast tube in the R-390A works is
> because the tubes it
> regulates are in series - not in parallel.
> 
> James A. (Andy) Moorer
> www.jamminpower.com
> 
> ----- Original Message ----- 
> 
> 
> >
> > Since you are playing with an SP-600, read issues
> 20 21 22 of "Electric
> > Radio" magazine. There are a number of improvement
> mods, and the mc1496
> > balanced mixer product detector is a winner.
> > 73...Steve..KJ8L
> >
> 
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> 



	
		
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