[Amps] Question re GU-74B grid current

[Roger]

On 10/22/2012 8:48 PM, Carl wrote:
>
> Thats being rather polite about it (-;
>
> Carl
> KM1H
>
>
>
>> 71% overall efficiency is remarkable for a class AB1 amplifier.

I was going to say something similar, but I think Carl has it about 
covered! <:-))

73

Roger (K8RI)


>
>>
>> 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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>>
>> --
>> Vic, K2VCO
>> Fresno CA
>> http://www.qsl.net/k2vco/
>>
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>
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