Kinda OT: Swan Mark I Linear expected output on 4-400A's in G-G?

[Multi-Volti Devices (Murray)]

4-400 fits in 3-500Z socket and was commonly used/available in GG years
ago---don't remember exactly what to do at the grid, whether it's DC ground
or RF ground thru capacitors, but I had similar amp, pulled 4-400's &
swapped new 3-400Z's

Murray
----- Original Message -----
From: "Keith Rowland" <k4kgw at ATTBI.COM>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Saturday, May 18, 2002 10:34 PM
Subject: Re: Kinda OT: Swan Mark I Linear expected output on 4-400A's in
G-G?


> First question:  How are you able to use the 4-400, which is a tetrode, in
place
> of the 3-400Z, which is a triode?  The 4-400 socket diagram is 4BK, while
the
> 3-400Z socket diagram is Fig. 3 (in the ARRL Handbook tube section).
>
> In any case, here are the operating parameters for the 4-400 in Grounded
Grid
> configuration (all figures are for a single tube):
>
> Plate Dissipation:  400 watts (Forced air cooling required)
> Max. plate voltage:  4000 volts
> Screen Dissipation (max):  35 watts
> Max. Screen Voltage:  600 volts
> Full ratings to 110 mHz
> For grounded grid operation:
> Plate Voltage:  2500
> Screen:  0 (control grid and screen grid tied together, making it in
effect a
> triode)
> Plate current:  80-270 ma. (single tone)
> Grid voltage:  0  Grid current, single tone:  100 ma.
> Screen current:  55 ma. (single tone)
> Single-tone driving power:  38 watts (single tone)
> Output power (single tone):  325 watts
>
> Anyway, regardless of how it's happening, with the above parameters and
two tubes,
> the expected output power is just what you are getting:  650 watts.
>
> Keith
>
>
>
>
>
> "Bob, WB2UJD" wrote:
>
> > OK you amplifier gurus,
> >
> > I have a Swan Mark I I have restored to mint condition and I am using 2
> > 4-400A's in G-G in place of the 3-400Z's (3-500Z predecessor) it was
designed
> > for.  It seems to work pretty well, but I am not sure it works as well
as it
> > might.
> >
> > What might I expect as a reasonable power output from such a
combination?
> > Here are a few pertinent details:
> >
> > 3.75 MHz, just over 650W out with about 112W drive (not 100% sure of the
> > HM-102 meter cal)
> > The Mark I has an untuned cathode driven input.
> > 2600V key down, 3300V idling, in operate (SSB) position
> > 240 mA plate current
> > 540 mA grid current (yes this is high, but tetrodes in G-G tend to do
this)
> > 90 mA grid current idling (bias)
> > Not 100% sure of metering cal either, but all metering resistors have
been
> > replaced and are 1% or better.
> >
> > DC plate input comes out as 624W.  Not sure how to calculate the grid
portion
> > or if this contributes to total DC input, probably does in some fashion.
> >
> > In Tune/CW position:
> > 3.75 MHz, about 450W out with about 112W drive
> > 1600V key down, 1900V idling
> > 300 mA plate current
> > 500 mA grid current
> > 55 mA grid current idling (bias)
> >
> > DC plate input comes out as 480W.
> >
> > I am looking for some idea of how the amp is doing and what might be
expected
> > of such an amp (Or how likely I am to piss people off if I were to
attempt to
> > use this amp on SSB!).  This is my first linear in close to 30 years as
a ham!
> >
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