[Johnson] Invader 2000 Grid Current

[Carl]

With decent tubes and correct voltage you can get up to 1200W out as PEP SSB 
or CW. When built the law was 1000W Input on CW (about 600 out) and 2000PEP 
on SSB  Many ran CW in the SSB position anyway on most all the old amps.

Carl
KM1H



----- Original Message ----- 
From: "David C. Hallam" <dhallam at knology.net>
To: "Johnson List" <johnson at mailman.qth.net>
Sent: Monday, March 17, 2014 6:35 PM
Subject: [Johnson] Invader 2000 Grid Current


>I just got the amp section of my 2000 in operation and have noted something 
>I don't understand.  According to the manual when tuning the finals, you 
>should hold the grid drive to 10 mA and tune to maximum output.  However 
>after tuning, following what I think is the manual procedure and switch to 
>SSB, I see the grid current meter kicking way up, like 25 mA, on voice 
>peaks.  As I understand operation of the finals is AB2.  Is 25 mA too much 
>grid current to maintain linear operation or is it normal?
>
> In CW mode, I can only get an input of 400 mA while I should be able to 
> reach about 475 mA.  The power supply is delivering 2100V under load.  I 
> attribute this to the unknown age and usage of the 4-400A finals, or this 
> is indicative of an overall problem.    I have not check the screen 
> voltage so there is the possibility it could be low.  The manual says 
> 500-530V.
>
> I have been using the Invader for several years in the 200W mode and get 
> an indicated 120W output on my Bird meter.  To, this indicates that the 
> driver is capable of full output.
>
> David
> KW4DH
>
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