Arto Rantala wrote:
When it does
happen, however, the picture shifts about 1 cm to the left and
becomes jittery. Mainly, consecutive horizontal lines are not aligned
perfectly, but individual lines can shift left or right on each
redraw, making the screen look like it shimmers very nervously.

Having turned the monitor back on and with the jitter continuing, I should
restate this part. The jitter is not quite so high frequency as to put each
line at a random position wrt other lines. Looking at the right side of the
screen, the wavelength of the wave inherent in the supposedly straight right
side edge is about 1-2 cm on average, putting around 20-30 waves per redraw,
putting the wobbling frequency around 2 kHz. I don't know if this is
relevant in any way, but I didn't want anyone to make conclusions based on
bad information.

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Arto Rantala