tek 5304 scope with wide bar trace
 

oscilloscope: tek 5304
display unit: D40
horizontal unit: 5B40
vertical units: 5A38 (i have two)

settings on the horiz unit are 0.1 sec/div and auto trig on.
everything else is off. settings on the vertical units (either unit
installed in either slot or both installed or both removed) do not
vary the results.

i get a vertical bar (instead of a nice dot) that spans from the top
of the display to the bottom and about 2 divisions wide that travels
across the display in about 1 second. intensity dial on display unit
has to be turned way up to see the bar. as i turn the sec/div up bar
speed slows down, and as sec/div decreases, bar speeds up.

if i pull the horiz unit (and the vert units), i get the same bar
about 2 divisions wide and from top of display to bottom, but it
doesn't move. i get the same result if i install on a vertical unit
(either unit in either slot).

i have the manual for the 5403 and the 5B40, but not the D40 nor the
5A38. the 5441 manual seems to have the schematics for the D41
display, which appears very similar to the D40. i used these
schematics and tek's scope troubleshooting guide to "common mode" the
amp stages on the vertical amp board and saw no changes to the
display. i have verified the power board's voltages per the 5304
manual.

right before i got the bar, the scope started repeating and phase
shifting the channel 1 trace that i was measuring. very quickly after
that i got the bar.

any help would be greatly appreciated, even if it's just pointing me
in the direction of the correct section to troubleshoot. thanks, and
sorry for the long post.