Tony wrote:
Most of the time, a smeared picture _is_ a fault in
the video amplifier,
though. But it may not be.
It can also be caused by use of a cheap video cable or a cheap KVM switch.
(Note that I deliberately used the word "cheap" rather than
"inexpensive".
I've seen expensive video cables and KVMs that were "cheap", and
inexpensive ones that were not "cheap".)