[Amps] Grounded Grid(Screen) 4CX250B power gain

[Hsu]

Hi,Alex
  There are some info on this web http://home.comcast.net/~k7rld/4cx250bamplifier.htm, and there is an article in  73 magazine march ,P50-54
S.W.Hochman,The Ample Amplifier,I only have a digest, not full article,anyone have this article?
   I think the 4CX250B cann't use GG configation as you mention" 
the classic connection",the grid power rating only 2W, indeed  exceed the grid dissipation limit easily!You are right.
 the only way use the configation like what I have mentioned,but the problem is the "triode" will have very low Mu,I'm afraid the 100W transceiver 
can not drive  a pair 4CX250B in GG configation.I do not know how much  exact power gain is this configation.
 73!Hsu

----- Original Message ----- 
From: "Alex Eban" <alexeban at gmail.com>
To: "'Hsu'" <hsu4qro at gmail.com>
Sent: Monday, July 13, 2009 2:53 PM
Subject: RE: [Amps] Grounded Grid(Screen) 4CX250B power gain


...makes me wonder: usually the grid AND the screen. are connected together,
not grid and cathode. Maybe I'm wrong. Could you please send me the
schematic?
If you mean the classic connection I would suggest that you be careful with
the drive; you can exceed the grid dissipation limit easily! 
Also the HV level can be a problem: for instance, my 4-1000 wants at least
3000VDC to behave like a high μ triode. 
Also, check if the 4-250 can operate in a high μ mode. If not you shall need
some cathode bias to keep the current to a safe level.
Alex  4Z5KS

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of Hsu
Sent: Saturday, July 11, 2009 3:45 PM
To: amps at contesting.com
Subject: Re: [Amps] Grounded Grid(Screen) 4CX250B power gain


 Hi, 
 Anyone have experience in grounded grid  a pair 4CX250Bs amplifier? could
you tell me how much power gain of this configation?
   This weekend, I'm planing to do a tube conversion in my friend's Henry
tempo 2001(a pair 3CX400A7),I have give up GI-7B due to its
 larger volume.The only choise is 4CX250B.The gride driven configation needs
screen and grid power supply,so I want to  use G-G configation
 (gird+cathode as cathode,screen as grid,  due to the 4CX250B   grid's few
power rating, it is low mu triode now).
 But I don't know its exact power gain,anyone can tell me about this?Thanks
in advance!
      73!
          Hsu 
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