Date: Mon, 5 Dec 2016 18:06:33 -0600
From: Joe <nss@mwt.net>
To: "amps@contesting.com" <amps@contesting.com>
Subject: [Amps] triode vs tetrode
OK like a 3-500Z, 3CX bla bla bla etc. are triodes, plate, grid, and
well filament.
Most of these tubes run grounded grid correct? so the grid is simply
grounded.
Now the 4CX bla bla bla is plate, screen, grid, and whatever filament etc.
What would happen if you simply wired it up like triode in grounded
grid. ground both the screen and the grid, has anyone ever tried that?
Joe WB9SBD
## That works good on tubes like the 4CX-3000 / 5000 / 10,000 / 15,000
Done on all the time. Requires more drive than a true Triode, and IMD is
a bit less.
## it also works on 4-125 / 4-250 / 4-400 A/B/C .
## This is yet another reason to directly bond the grids to chassis on any
SB-220 / L4B / Henry Amp / TL-922. Then you can shovel
a 4-400 A / B / C directly into any 3-500Z amp, and it will run just fine,
albeit with less idle current, and slightly higher drive requirements.
## On tubes like the 4CX-1000 / 1500, the grid dissipation is non existent.
0 watts on the 1000..and only 1 watt on the 1500. In those cases, the
config used is called... super cathode driven. The control grid is bonded to
the
cathode. The screen grid is bonded to the chassis. But higher drive is
required.
A 4CX-1000 will require 160 w of drive to get 1200 w pep out. I know 2 x VE7
folks who use that config, and it works just fine with no imd issues.
Jim VE7RF
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