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[AMPS] SB-220: Operate/Standby Switch

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Subject: [AMPS] SB-220: Operate/Standby Switch
From: W8JI@contesting.com (Tom Rauch)
Date: Tue, 6 Feb 2001 20:27:52 -0500
> > I don't believe its an issue of filamant "failure" or tube returns
> > but one of reduced emission life.  The addition of a simple rheostat
> > to the power tube's filament circuit makes good engineering and
> > economic sense.
> >
> > -Paul, W9AC
> 
> Amen, Paul.
> We are prolonging emisson here. An added bonus of a resistor/rheostat
> in the primary of the filament transformer is a bit of inrush
> protection that is there all the time.

Put all those tubes laying around that are perfectly good except for 
low emission in one pile. 

Put all the tubes with internal defects like broken welds, leaking 
seals, open filaments, grids touching cathodes, and on and on in 
another.

Now use common sense.

Factually, emission life is an issue when the tube is operated at 
25% of its capability in uninterrupted commercial service. In 
amateur applications, its mostly something for people to talk about.


73, Tom W8JI
w8ji@contesting.com

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