----- Original Message -----
From: "Ron Youvan" <ka4inm@tampabay.rr.com>
To: "amps" <amps@contesting.com>
Sent: Saturday, January 28, 2012 3:23 PM
Subject: Re: [Amps] 4CX1000A
> Val LZ1VB wrote:
>
>> Thank you very much for the explanation. I completely agree.
>> The question is how a tube, showing maximum reverse screen current
>> leading
>> to an excessive screen dissipation could be used in an amateur amplifier.
>> Yes, the screen is in a danger only when the amplifier is moderate
>> driven,
>> but the PA is supposed to work at any drive level from 0 to max.
>
> I'm not mike, but I think the reverse screen current is not strictly
> normal, in a perfectly built
> tube you should see none.
> These tube are built with the screen grid components hiding in the
> electron shadow of the control
> grid elements. When the alignment isn't perfect the electron beam strafes
> the side of the G2
> elements which produces emission via secondary emission.
> I suspect most new good tubes of this kind show negotiable emission.
> Those that do emit
> significantly may find their way onto the hands of HAMS more easily.
> --
> Ron KA4INM - Did you know ...
> ... that no-one ever reads these things?
>
I suggest reading page 4 and 5 in the below link.
http://www.g8wrb.org/data/Eimac/4CX1000A.pdf
And then tell me its not perfectly normal. Most external anode tetrodes Im
familiar from the 4X150A to 4CX1500B can exhibit negative screen current.
Carl
KM1H
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