I have a mitsubishi 17" monitor, TFS6705SETKL which has an irritating
problem.
The size of the vertical raster keeps wandering up and down randomly,
sometimes it's stays fine for a period, but mostly keeps moving about.

I looked at the vertical deflection schematic, and the vertical deflection
circuit is pretty much an "IC", with some external caps/r's, and the size,
position is controlled by processor controlled dacs on a separate card (for
which I don't have the schematic). The size is controlled by a current into
the IC so I can't look at this with a scope to see if this is at fault.

The ramp generator looks fine, but the ramp on the output from the vertical
deflection IC that drives the coil is wandering up and down, and running
into the supply rail where it limits. The centre voltage is stable on the
other side of the coil.

It does look like the vertical delfection IC could be at fault, but it could
be the DAC ?Does anyone have any ideas what type of faults might be causing
this problem in either scenario ?

Regards
Tony