I don't think any are used in the vertical amplifiers of
either the 547 or 556 (which are nearly identical designs
BTW), as these are all transistorized, except the first
stage cathode follower which is a 12AT7. The other tubes
in the 547 are all single and dual sided tubes commonly
used in several Tek scopes.
The
556 uses two 6M11 triple triodes, one in each sweep
generator.
There is a novel miller integrator
sweep generator design
which can be implemented as a one tube design using a
combination
pentode-triode tube. The Miller integrator itself is
named a
"Phastastitron" short for fantastic. This cleaver design
uses a
single pentode for all of the functions of the sweep
generator, including the
cut off diodes and synchronization (rather than triggered
operation.) The
screens are used as additional grids in this design. The
triode serves as
a cathode follower, to prevent the external load from
altering the timing
linearity. Tek never used this design, as all Tek scopes
have triggered
rather than synchronized to the input signal. It
is useful if you want to design one of
those “three tube scopes”.
- Steve
