Wow Ian,
I had totally missed that. The input circuits were right next to the grid
circuit and I had simply assumed. Well how about that. Hmmm, very
interesting. Kinda burst the bubble for me. I must be blind and deaf.....
n Mon, 7 Nov 2005 14:43:00 +0000 Ian White G/GM3SEK
<gm3sek@ifwtech.co.uk> exclaimed:
> Shawn Tayler wrote:
> >
> >Hello Rich,
> >
> >Interesting that you say this. I was under that same impression from
> >conversations through the years. I was happy to find that only the
> >screen is grounded, for stability. The 30S-1 is a grid driven tetrode
> >amp otherwise.
> >
> The 30S-1 is cathode driven (I'm looking at the schematic now). G1 is
> mostly grounded to RF by a 220pF capacitor, but RF negative feedback is
> also applied at this point by a 5pF cap from the anode.
>
> > I could never see how a 4CX1000A could function well in a
> >grounded grid mode.
>
> G1 has normal negative bias, the same as it would have in grounded
> cathode, so the tube operates in normal class AB1. The first traces of
> grid current will operate a transformer-coupled ALC circuit - but grid
> bias supply has quite a high impedance, so if the ALC output has not
> been connected back to the exciter, any grid current will cause a large
> shift in operating point with resultant IMD.
>
> These features make the 30S-1 very different from the "triode-connected
> grounded grid" operation of 4-250/400/1000 jamjars with G1 and G2 both
> connected to chassis ground.
>
>
> --
> 73 from Ian G/GM3SEK
> http://www.ifwtech.co.uk/g3sek
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
--
Mitchell's Law of Committees:
Any simple problem can be made insoluble if enough meetings are
held to discuss it.
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|