[Yamamaya42]

The broken scale wheel is an annoyance but by no means a stop, you should be able to work out what the sets are using the other channel, since it's a dual scope, every scope has a calibrate output for the probe, set everything to the calibrated point, and with both channels showing, set the non broken one to any arbitrary input level 5,10, 2v what ever, hook that input to the calibrate probe output, note how many steps it shows on the screen (scale), change to the broken side, switch around till it matches, you have found that setting that the non broken one is set to, mark it with some kind of permanent marker, you now have a known start point to where you can count to the other settings.