[Amps] triode vs tetrode

[Paul Kraemer]

I recall a article in QST or CQ a long time ago something to do with tapping 
the screen on the filament choke to improve using tetrodes in gg?
Written by the two Eimac engineers but can't find it these days
Anyone remember that?
Paul K0UYA

-----Original Message----- 
From: Rex Greenwell
Sent: Tuesday, December 06, 2016 5:28 AM
To: amps at contesting.com
Subject: [Amps] triode vs tetrode

Eimac had a bulletin out describing the 4-1000A tetrode in grounded
grid, it states  "Most tetrodes do not perform satisfactorily when
connected as a high-mu triodes.  Control grid dissipation usually limits
their power handling capability when they are connected in this
manner.   The 4-1000A is an exception to this rule if a plate voltage of
at least 3000 volts is used. " With a plate voltage above 3000 volts a
4-1000A is a legal limit plus amplifier in grounded grid.  I can supply
a pdf of this bulletin should anyone desire.

It has long been known that 4-400 tetrodes operate satisfactorily in
grounded grid as well.  They will plug-in replace 3-500Z finals in the
SB-220 and variant amplifiers when all of the grid pins on the sockets
are connected directly to ground with low inductance leads.  This is how
the 3-500Z tube sockets should be wired in any event whether to use
4-400s as finals or not.   The original SB-220 and other designs using
RF chokes and bypass caps on the grid leads proved to be a poor idea.

K0KP

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