[Moon-net] regarding the coming 2x4CX250 Amp

Kim Liljekrans [OZ5IQ] kim at oz5iq.dk
Fri Nov 7 19:59:24 CET 2008

The Q´s from Jordan   regarding his coming 2x4CX250  Amp.

HI Gang / Jordan

RE:   I'd like to have 10mA on idle

Its  ALL too less  !!  Stay LINEAR, and this can you only do, by :

Stabilizing the G2  ( and G1 ) voltages !   The  G2  IS espicially important  !

First of all - why do you want to swich the HV depending on the band you are using  ??

You have ONLY to swap the G2  voltage, the the desired purpose./ band operation.

Regarding the current :

Each tube may use 15 -20 mA  EACH  during  normal operation  (SSB) .

This MEANS, that a MINIMUM of current flowing in the stab unit for the G2,  MUST be LESS than tis value ! -  otherwise, your tubes will be driven into unlinearity  !

I / we have been running the old K2RIW  Amp for mni years, with stabilizing tubes for the G2,  becource of the matter that the I G2  may both be positive  AND  negative ! The last means, that the tubes are pumbing current OUT of the g2 pin, and many persons have realized, that their G2 supply unit, simply burns off !

Why ?

IF normally ie 25 mA  is flowing through the "stabilizing unit"  and suddenly the tubes  generates / is pumping out "  more current -  the result might be, that the unit burns off ! / goes unlinear .

The point is :  

That you need a Constant voltage, with a ie capability of a constant current flow of ie 30 mA . This will give you, the possibility to use  a " part"  of the current, to the tubes,  but without  the voltage rises or drops  !

Thats what you need  !

I have NOT  a solution, with semiconductors,  otherwice than a  constant  consumption of the max current, and with proper capability to handle both negative  and positive currents,  as f.eks.  a a pair of OB2  in series  (    150V stab tubes )
in series.

Again, any good solutions ? ways of handling this phemenonema  ?

VY 73  de  OZ5IQ, Kim    and with stabtubes in the old K2RIW Amp now 6M.
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