Re: [Amps] Question re GU-74B grid current

["Carl" <km1h@jeremy.mv.com>]

Yeah sure. A 600W rated tube fraudently labled 800W to grab US dollars. At 
least ACOM has erased the GU74B for a 4CX800A even tho running them just as 
hard.
They will soon go the way of the dodo bird unless the Chinese copy and maybe 
improve it.
Carl
KM1H



----- Original Message ----- 
From: "Leigh Turner" <invertech@frontierisp.net.au>
To: <amps@contesting.com>
Sent: Monday, October 22, 2012 9:28 PM
Subject: Re: [Amps] Question re GU-74B grid current


> Yes, the ACOM-1000 and ACOM-2000A are two good examples of what good amp
> designers can do with good tubes.  These GU74B tube based amplifier 
> products
> have been immensely successful for ACOM and others.
>
> Jim you are absolutely right to be interested in what amp builders are
> actually getting and experiencing from these fine tubes, rather than rely
> only on information gleaned from the translated GU74B Russian data/spec
> sheets. Unlike the savvy folk, many are not aware of the full picture in
> respect of how good these conservatively rated mil-spec tubes actually 
> are.
> Leigh
> VK5KLT
>
>
> -----Original Message-----
> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Carl
> Sent: Tuesday, 23 October 2012 11:19 AM
> To: Vic K2VCO; amps@contesting.com
> Subject: Re: [Amps] Question re GU-74B grid current
>
>
> Thats being rather polite about it (-;
>
> Carl
> KM1H
>
>
>
> > 71% overall efficiency is remarkable for a class AB1 amplifier.
>
> > On 10/22/2012 12:10 PM, Val wrote:
> > > Jim,
> > >
> > > ACOM1000 and ACOM2000A are without doubt the most popular amplifiers
> > > based on GU74B. Many thousands of them are working under the following
> > > conditions at1000W output:
> > >
> > > Plate  2350-2400V
> > > Screen 340V
> > > Anode current 510-580mA
> > > Bias between -45 and -65V for 220 mA idling current (the EBS keeps the
> > > bias between -65 and -75V for idling current of 70 mA when no RF drive)
> > > Normally the grid current is well below 10mA where the grid protection
> > > trips.
> > >
> > > 73, Val LZ1VB
> > >
> > >
> > > Could somebody advise me as to the resting plate current and operating
> > > ctrl grid bias voltage they are using on a GU-74B (plate voltage is
> > > 2500V, screen grid 300V)? Also, does the tube draw grid current? I
> > > realize that in AB1, no grid current should be drawn, but the tube
> > > characteristic curves predict about 15mA grid current at full output
> > > (1000W output, 600mA anode current (per tube) and 250W resting
> > > dissipation. I am interesting in what builders are actually getting,
> > > and not information from data or spec sheets.
> > >
> > > Tnx and 73,
> > >
> > > Jim W8ZR
>
>
>
>
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