If the monitor is a CRT, a focus problem generally requires
a bit of tweaking inside - which is NOT diy-able re 25kV.
Ensure any speakers nearby are magnetically shielded.
If the monitor is TFT, adjusting "focus" is important as
some TFTs seem to have somewhat poor default settings.
Other factors are cable quality - if the monitor is a CRT
with 5x BNC input option, a decent BNC lead can help.
