[Johnson] Question for Invader 2000 Owners

[David C. Hallam]

Ed,

I agree that 180/190 mA is about right for a pair of 4-400A with a 
screen voltage of 500A and grid bias of -72V.  From the 4-400A data 
sheet this is what Eimac says is typical operation for a pair of 
4-400A's in AB_2 .

Johnson used PL-175's in early versions of the Invader 2000 until Penta 
quit making them.  I have constant current curves for the PL-175.  
Looking at them under the same conditions a PL-175 should have a zero 
signal plate current of about 140 mA or 280 mA for a pair under the same 
conditions.

I happen to have a pair of PL-175's.  I might put them in the Invader 
just to see what the zero signal plate current is.

David
KW4DH

On 4/26/2011 11:16 PM, ewirtz wrote:
> On 4/26/2011 11:58 AM, David C. Hallam wrote:
>> In the Invader 2000 manual in the Linear Operation Loading Current
>> section, you are instruction to measure static plate current.  That
>> value is used to determine a loading current from the chart in the
>> manual.  The example given for the procedure is 280 mA resting current
>> equals 320 mA of loading current.
>>
>> I have two questions:  What value of resting current do you have in your
>> 2000 and do you have PL-175's or 4-400A's?  I have 180 mA with 4-400A's
>>
>> David
>> KW4DH
>>
> David,
>
> I don't have an Invader 2000 but I do have a Thunderbolt Amplifier 
> with 4-400s. In my opinion 180 ma idling current is about right for 
> the available plate voltage and the operating class of AB2. From that 
> point you can easily get up to 500 ma at full load on SSB. AM linear 
> will be quite a bit below that. I load my TBolt to about 350 ma for AM 
> linear and it runs quite well with little distortion.
>
> Hope this helps.
>
> 73,
>
> Ed, KØBKA
>
>

-- 
"I predict future happiness for Americans if they can prevent the government from wasting the labors of the people under the pretense of taking care of them."
Thomas Jefferson


"We may consider each generation as a distinct nation, with a right, by the will of its majority, to bind themselves, but none to bind the succeeding generation, more than the inhabitants of another country."
Thomas Jefferson