tektronics 503 scope

So, what's your (or anyone else's, for that matter) opinion on the Tek 465B? I bought a used one as a Christmas gift for my partner; with two probes, an original manual, and shipping, it was around $600. It appears to work fine except that when I connect the probes to the square-wave calibration output, the horizontal portions of the waves seem to be much "thicker" vertically than they should be. The vertical portions appear to be reasonably sharp, however. I've tried turning down the intensity and twiddling the focus and astigmatism adjustments, but it's not as sharp as I would like to see. I can probably trade it for another one, but it means more shipping and possibly late for Xmas. Anyone know if there's another adjustment I'm missing? I've only got the user's guide - not the service manual.