"JANA" wrote in message
...
It looks like Moray effect from the aperture grill (lines) beating against
the scan lines. Does the effect vary when you move the centring, height,
or
other scan parameters?

It does, but it also varies if I swivel the monitor left or right. This
makes me think it's something external influencing the beam.

If the beam focus is slightly off its proper setting, it is possible to
have
these lines emphasized. The focus performance can change with the aging of
the CRT, or something has changed in the focus supply from the HV
multiplier.

But the effect was totally gone when at the shop...

As for black shadows on the edges of highlighted lines, this can be caused
by capacitors that have drifted off value, or the CRT is going a little
weak. The shadows are caused by the effective video low frequency response
being rolled off a little.

There are no black shadows around anything. There *are* shadows of red,
green, or blue depending on which section of the screen you are looking.
They appear around black text on a white background, and they correspond to
the pattern mentioned above. I'm sure it's just the same problem but only
visible where black borders on white.