Re: [Amps] 3.5 kV 2A REGULATED Power Supply: Schematic ?

[Gary Schafer <garyschafer@comcast.net>]

I think he is just being stubborn.  :>)

There is nothing wrong with running the exciter and power amp at below 
maximum level. As Rich points out "that is the proper way to run them".

The exciter should be loaded and operated at its "best operating point" 
and its pep limited to that amount. The amount of drive applied to the 
amp from that exciter should be adjusted so that the maximum pep never 
drives the amp into grid current. This can be done with an attenuater 
between the exciter and amp as an example.

With a tube like a 4CX1000 it may be an advantage to have a rather high 
impedance bias supply rather than one that is "regulated". As that tube 
is rated at zero grid dissipation, it can stand only the slightest 
amount of grid current. By allowing the bias to increase as grid current 
is attempted protects the grid from drawing excess current.
Normal operation should be adjusted so as to never draw grid current.

73
Gary  K4FMX


GGLL wrote:
> I've been following this nice discussion, and want to ask something 
> about Ian's post, ¿what's bad with running exciter at a lower level and 
> to have the amplifier "seriously under-driven"? (it seems to be not only 
> a lower power output matter).
> My modest guess is something related with operating points due to  
> distortion considerations, is it?.
>
> Many thanks and have all a prosperous 2004
> Guillermo - LU8EYW.
>
> Ian White, G3SEK wrote:
>
> > R. Measures wrote:
> >
> > > **  The grid does not and can not draw current when a competent 
> > > operator sets the grid potential just above the level where it can 
> > > draw grid-current with the max PEP drive that's available.
> >
> >
> >
> > That is only true if the grid input circuit is guaranteed to be able 
> > to soak up all possible levels of drive without allowing grid 
> > current... but that also has disadvantages: either the exciter runs 
> > flat-out and generates unnecessary IMD of its own, or else the exciter 
> > runs at a lower level and the amplifier is seriously under-driven.
> >
> > I truly cannot see why anyone should design (or defend) a 
> > high-impedance bias supply whose voltage regulation will collapse at 
> > the first trace of either normal or negative grid current. What's the 
> > point, when a better-regulated supply is just as easy?
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