If the position control will move what trace you do have to the right,
that might eliminate the output stage. Look for it on the print, in
some scopes it is a dual pot wired in llike an "X" formation and may
feed the CRT plates "directly", but I don't think Tektronix does this.
(they have good reason on an engineering level)

I would definitely check it in XY the very next thing. If it works
properly in XY you've eliminated the entire amplifier section and can
proceed directly to the oscillator. However if whatever you try to
display compresses on the right, you know it's that amp, and whether
the position control moves the flattened portion or not is the next
test. If the whole squished trace moves, it is before the position
control, if the trace squishes (love those technical terms) without
reaching the right side then it is after the position control.

If the problem is one of the output stages to the plates, the non
linear portion of the trace whould exhibit defocussing or astigmatism,
I think. It may not with certain CRT designs. To go any farther I'll
have to get the print, but this should be a good wham bam eliminate a
bunch of stuff. In other words, quichly find out what it uisn't/u.

JURB