[Amps] HF-2000 amp problem?

[TexasRF at aol.com]

Hi Jim, heavier loading causes more cathode current to flow to the plate  and 
less to the grid. 
 
Heavier loading implies that the plate load impedance is lower and there  
will be more plate current flow as a result. The total cathode current would be  
about the same so the grid current would have to decrease as the plate current 
 increases.
 
73,
Gerald K5GW
 
 
In a message dated 4/16/2007 8:48:26 A.M. Central Daylight Time,  
k7rdx at charter.net writes:

Would  not loading heavier cause the grid current to be even higher?Jim..
-----  Original Message ----- 
From: <TexasRF at aol.com>
To:  <Paul at PaulFerguson.us>; <amps at contesting.com>
Sent: Saturday,  April 14, 2007 9:28 AM
Subject: Re: [Amps] HF-2000 amp  problem?


>
> Sounds like you need to increase the drive to  50-75w like 20m and load
> heavier (less load C) for maximum  output.
>
> If this scares you, load heavier first and then  increase the drive  power.
>
> 73,
> Gerald  K5GW
>
> In a message dated 4/14/2007 10:25:05 A.M. Central  Daylight Time,
> Paul at PaulFerguson.us writes:
>
> I have  a  10-year-old QRO HF-2000 amp. It has two Amperex 3-500Z
> tubes.  You can see  info on it at: http://www.qrotec.com/
>
> It  used to output 1,000 watts or  so on all bands. Now it outputs
>  1,000 watts up to 20 meters, but only  about 500 watts on 17  meters
> thru 10 meters.
>
> On 20 meters and  lower,  grid current runs about 150 ma and plate
> current about 500 ma.   Plate voltage is about 2,800. Input power runs
> 50 - 75  watts.
>
> On  17 meters and higher, grid current is about  100 - 150 ma and plate
> current  is 250 - 300 ma. A small increase  in input power gives a
> large increase in  grid current and little  additional output power.
> Input power is 30 - 40   watts.
>
> The amps tuned inputs seem OK as the transceiver sees  an SWR of  1.1 -
> 1.3.
>
> All measurements were taken  using a 50 ohm dummy  load.
>
> Any ideas as to what might be  the problem?
>
> 73,
> Paul -  K5ESW
> Raleigh,  NC
>
>
>
>
>
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