[old_tv_nut]

The caps that could reduce this problem are not the main power supply (electrolytic) caps, but small ones on the power input (if they exist). There may also be a relatively small coil or coils involved at that point. A schematic would help give a hint about what to look at.

The slow scroll tells you that the source is running from the 60.0 Hz power.
Is it a single line, or a bunch of lines? A bunch of lines, each rapidly flickering on and disappearing while the whole bunch slowly scrolls is probably motor interference.