[Boatanchors] 1625 tube

[Glen Zook]

Actually, in every 807 tube that I know of the
supressor grid is connected internally in the glass
envelope to the cathode.  It is the 1625 that in some
brands the supressor grid comes out of the glass
envelope and is connected by a separate wire to the
cathode.  It is these 1625 tubes that could be
modified to use in ground-grid linear amplifiers (as
you described) and not any of the 807 tubes.  Since
the supressor grid cannot be isolated the 807 cannot
be used in a grounded-grid circuit.

There were circuits for these published in various
ARRL publications and at least one commercial linear
amplifier manufacturer furnished one model of their
linear amplifier that used the modified 1625 tubes. 
This linear was also available using, if I remember
correctly, the 837 for the amplifier tubes.



--- Vic Rosenthal <vic at rakefet.com> wrote:

More 1625 trivia: one other difference between the
1625 and 807 that should be noted is that the 1625 has
its supressor grid internally connected to the 
cathode, whereas it goes to one of the base pins in
the 807.  This means that you cannot use an unmodified
1625 in a gg amplifier.


=====
Glen, K9STH

Web sites

http://home.comcast.net/~k9sth
http://home.comcast.net/~zcomco


		
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