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Re: [Amps] GU 74 operating parameters

To: "DF3KV" <df3kv@t-online.de>, <amps@contesting.com>
Subject: Re: [Amps] GU 74 operating parameters
From: "Carl" <km1h@jeremy.mv.com>
Date: Wed, 6 Jan 2010 19:39:43 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Svetlana marketed the GU-74b as the 4CX800A and changed the specs to 
increase power as well as set a very high idle current to obtain barely 
acceptable IMD.

Carl
KM1H


----- Original Message ----- 
From: "DF3KV" <df3kv@t-online.de>
To: <amps@contesting.com>
Sent: Wednesday, January 06, 2010 5:19 PM
Subject: Re: [Amps] GU 74 operating parameters


Who manufactures a 4CX800?
Is that not a pseudo designation of the GU74b, as they do with the GU43b
which the Russian dealers advertise as a 4CX1000? OR the GI23b as a 4CX1600?

My calculations for class AB1 at 2100V anode voltage swing and 0.6 anode
current are resulting in a plate load impedance of 2200 ohms.

73
Peter

-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Karl-Arne Markström
Sent: Mittwoch, 6. Januar 2010 19:56
To: Ulf Tjerneld; Amps@contesting.com
Subject: Re: [Amps] GU 74 operating parameters

First, the quoted limits apply to the 4CX800, for the Russian GU74B they are

2000V and 0,5 A respectively.

Assuming you will "get away" with the 4CX800 ratings,
the plate voltage swing will be limited downwards by the screen voltage. It
is reasonable to expect a peak plate voltage swing of around 2100 V with a
300 V screen voltage and a 2500V no-load voltage. This translates roughly
into a plate load impedance of 2800 ohms at the 1 kW output power level.

A PI-L network using a plate load impedance of  2800 ohms and an
intermediate impedance of 200 ohms would be a good starting point.

73/

Karl-Arne
SM0AOM

----- Original Message ----- 
From: "Ulf Tjerneld" <star@frizon.org>
To: <Amps@contesting.com>
Sent: Wednesday, January 06, 2010 7:26 PM
Subject: [Amps] GU 74 operating parameters


>
> Hi all,
>
> I'm building my first amplifier - or my first serious amplifier that is.
> The chosen tube is a GU74B and I'm wondering about the operating
> parameters when I'm designing the Pi-L filter. I have of course read the
> specs sheets where a maximum plate current of 800mA at a plate voltage of
> 2500 volts is stated. But what I really would like to know are the "best"
> conditions to operate this tube under. I guess I will get different
> answers from all of you, but it would help me anyway to decide on
> something to use as as a basis for tank calculations.
>
> My PSU will deliver 2500 volts under no-load conditions.
>
> Thanks!
>
> 73's
>
> Ulf /SM0NOR
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps


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