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

To: <amps@contesting.com>
Subject: Re: [Amps] Grounded Grid(Screen) 4CX250B power gain
From: "Hsu" <hsu4qro@gmail.com>
Date: Mon, 13 Jul 2009 16:33:22 +0800
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Sorry,I missed the year:here is an article in  73 magazine ,March 1973 ,P50-54
      S.W.Hochman,The Ample Amplifier.

----- Original Message ----- 
From: "Hsu" <hsu4qro@gmail.com>
To: "Alex Eban" <alexeban@gmail.com>
Cc: <amps@contesting.com>
Sent: Monday, July 13, 2009 4:22 PM
Subject: Re: [Amps] Grounded Grid(Screen) 4CX250B power gain


> 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@gmail.com>
> To: "'Hsu'" <hsu4qro@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@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Hsu
> Sent: Saturday, July 11, 2009 3:45 PM
> To: amps@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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