[Boatanchors] 1625 tube

[rkerr]

There was just such a linear amplifier using four modified 1625s in 
parallel grounded grid in the 1957 Radio Amateur's Handbook.  The 
article mentioned how to modify the suppressor grid connection by 
reconnecting wires in the base, and also that some 1625s had the 
suppressor connected to the cathode inside the glass envelope, a la the 
807, and therefore could not be used in this configuration.

Bob
WB4TGG


Glen Zook wrote:

>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
>
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