[Johnson] Invader 2000

[David C. Hallam]

I would like to hear from owners of a Invader 2000 about their operating
experiences with the 2000.  I know that at some point Johnson replaced the
original PL-175A finals with 4-400A which has close but not identical
operating parameters.  However to the best of my knowledge, they never
released any revised parameters.  My questions center around the section in
the manual concerning linear operation loading current.  The example in the
manual assumes a static plate current of 280 mA and the graph has a minimum
of 200 mA static plate current.

My 2000 has a static plate current of 180 mA.  According to the Eimac
constant current curves of a 4-400A at -75VDC on the grid, 2200 VDC on the
plate, and 500 VDC on the screen, plate current should be 90 mA.  This
indicates that my static plate current is correct for the operating
conditions of my 2000.

I also have the Penta constant current curves for the PL-175A.  Inspections
of the curves show that under identical conditions, the PL-175A should have
a static plate current of 100 mA or 200 mA for a pair.

All of this indicates to me that the graph in the manual is skewed too far
to the right.  The operating line on the graph is a straight line so maybe
simply extrapolating the line to the left would be acceptable.

What value(s) of static plate current (ZSAC) do others get with Johnson's
nominal conditions of plate, screen, and grid values for the PL-175A and/or
4-400A?

David
KC2JD/4