I have a Tektronix 465M scope (AN/USM-425(v)1 with an odd problem. I first noted that the trailing edges of square waves seemed to slope backwards. A little troubleshooting led me to the following, which seems to be in the vertical deflection amplifier.
Placing the unit in X-Y mode and attaching a sinewave to Channel one I adjust the amplitude and trace rotation to get a perfectly horizontal trace on the graticle centerline. Disconnecting channel 1 and connecting the same signal to channel 2, I *should* get a perfectly vertical line. Instead, I get one that is slanted almost two minor divisions top to bottom. That is, if the to of the line is at the exact center of the top line of the scale, the bottom of the vertical line is almost two minor divisions to the left of the center of the bottom line of the scale.
It's like the vertical axis is rotated, but the horizontal axis is fine.