May want to do some testing of diodes and resistors while the set is
running. I would replace all the caps in the horizontal and drive
section because one may show good but can be bad. I would also
replace those parts that was mentioned in one of the previous post
for parts sometimes test good but can be bad. But it does look like
it may have a B+ problem. Is your B+ at the proper voltage ? Also may
want to replace your horizontal output if you have a spare one there.
What happens when you turn the screen control on the flyback down
does it still show the line on that one side ? This problem can also
be caused by a bad yoke. I will take a look the schematic over the
weekend and see what I may come up with. But check your B+ line.