Once you have the pinout of the tube, just test it in circuit. Like
with a transistor, emitter and base waveforms give you and idea of what
should be on the collector. With tubes the waveforms on the grid and
cathode give you an idea what should be on the plate.

Be on watch for those inductive loads, they can trip you up a bit. If
you're going to work on equipment with tubes, I suggest you get a 100:1
scope probe.

Also be aware of screen grids, if it's not a triode, lack of bias on
the screen can make the tube appear to have low or no emission. Think
of a tetrode or pentode as a dual gate depletion mode N channel FET. A
high voltage FET. (usually)

JURB