RE: NJ4F's Y131A Eimac socket.
The Y131A is similar to SK800B, used for 4CX1000A, 4CX1500B. However, it is
for Grounded Screen application, and has no built in screen bypass like the
800B has (1.5nF). Collins and now Continental Electronics used to use hard
grounded screen for similar tubes and for the 5CX1500A in their FM
broadcast rigs. They float the cathode (filament transformer is isolated
for screen voltage) and apply negative potential there, to do the same
thing. Of course this means the grid bias has to be somewhere even more
negative than the filament bias, so that power supply is usually tacked in
series there.
By hard grounding the screen, the tetrodes give better isolation (grid to
plate feedthrough) for VHF. This eliminated some of the hurdles of
neutralization, but it still is advisable. It makes the screen bypass go
away, and leaves only cathode bypassing for the designer to contend with.
K5PRO
John
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|