[Amps] 4CX1000A

[Carl]

----- Original Message ----- 
From: "Ron Youvan" <ka4inm at tampabay.rr.com>
To: "amps" <amps at 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