I have an HP 21" Trinitron monitor (HP A4576A). Since I got it, it has been
blurry at the left and right edges of the screen. It also has a wobbling to
the display, most noticeable at either edge, whenever I have the refresh
rate set to something other than 60 hz, and it's been turned on for a few
hours. I'm trying to get around to getting it looked at somewhere, but I
had the thought recently that maybe these two problems are related, and I'd
like to see what the repair shop comes up with as the cause of the problem.

Is it possible that what's happening is some AC is getting through the power
supply in the monitor, and affecting the scan of the image? It would make
sense (to me) in that case that the problems (blurriness *AND* the shaking)
both go away at 60hz, since I have 60hz AC. The other possibility would be
some EM interference, but I've tried the monitor at different angles, in
different rooms, and connected to different sources, and it behaves the
same.

I've been able to make the image decent by adjusting the focus so that the
edges are reasonably clear (as clear as I can get them), but then the centre
starts to bleed. This can be minimized by dropping down the contrast
though. Maybe this points to something else as the cause of the problem.
In any case, it always seems to look great at 60hz, so I"m hoping it's not
simply just a tired tube.. the monitor is 5 years old and hasn't seen much
use (sat unused for a few years I was told) so I would hope it's got some
life left still.

Any ideas would be appreciated.