开云体育

Hi Peter,

Besides the check to the power supply's capacitors, as Chuck noted and, as you will notice follwoing up the threads, is a kind of "standard" advice for all equipment of this vintage...
It may be helpful (for further troubleshooting by the group or yourself) if we can differentiate if the wide trace is due to problem with focus, or if it's wideband noise related..

Since you mentioned that readout is fine, there's less likelihood of being focus related, but still, not being familiar to the 2445's focus circuitry, there can still be an explanation for a focus problem while drawing the actual signal trace on screen, as many scopes have "auto-focus", circuitry that dynamically adjusts the focus for the often different intensity of the readout.

To rule-out focus from noise, it usually suffices to display a good square wave on the screen (e.g. calibrator).
At moderate sweep speeds, such as enough to display a single cycle on screen, the rising and or falling edge should look cleaner and sharper (while the tops and bottoms still look fat) if the issue is noise related. At slower sweep speeds it won't be much conclusive as you would barely see the rising and falling edges.
However, if the "fat" is due to focus, the rising or falling edges are likely to show just as fat.

Other resource to help rule-out noise as a source, is turn on the Bandwidth limit (usually to 20MHz)... this usually makes a "fat" noisy baseline to look sharper (if the issue is noise).
If, however, engaging BW limit doesn't improve matters, than it may tend more to be focus related.

Rgrds,

Fabio