See correction below:
----- Original Message -----
From: "Carl" <km1h@jeremy.mv.com>
To: "Leigh Turner" <invertech@frontierisp.net.au>; <amps@contesting.com>
Sent: Monday, October 22, 2012 9:56 PM
Subject: Re: [Amps] Question re GU-74B grid current
> Yeah sure. A 600W rated tube fraudently labled 800W to grab US dollars. At
> least ACOM has NOT 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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>
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