> From: Andrew Williamson <andrew@gi0nwg.demon.co.uk>
> Subject: Re: [AMPS] Tuning Up?
To: <amps@contesting.com>
> Date: Mon, 18 Aug 97 07:49:59 +0000
> Now I know how to *properly* tune up my pair of 3-500Z's ;-)
Not quite. ;-)
> So, for a different type of amp using a pair of 4CX800's (a ETO 91b) any
> useful tips out there on tuning?
I'd follow ETO's instructions, unless there is something lacking or
incorrect. Dick Erhorn is a successful amp designer with a good
reputation, and likely would have been a guy stuck with a web page
as his only credit if it wasn't.
Tetrode amps are more complex and difficult to tune than cathode
driven trodes , and often require special tuning procedures. But no
matter WHAT type of amp you use, it ALWAYS has to be loaded at the
full expected peak power from the exciter or it will splatter.
Screen current does indicate proper operation in a tetrode, just as
control grid current does in an AB2 cathode driven amp. Keep the
screen within dissipation limits (the amp SHOULD have protection for
that) and tune just beyond the point of maximum output with full
expected drive.
The load control sets the amount of screen current at resonance, and
the tune (plate) control should always be set for maximum output
power unless the manufacturer indicates otherwise.
73 Tom
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