I have a used 2230 that I have been using to view traces etc. I fiddled with the horizontal scale and now I cannot see a trace at all. I have used beam finder and it shows, and I have messed with focus and intensity. The channel is set to A and I have been twiddling knobs for hours to no avail. No trace.
Where did it go and how can I get it back??

Where did it go and how can I get it back??