I have been fiddling and can add some more information regarding the pen
I swapped the motherboards between two machines, a 2000 and the 2100 with
the problem and the error was not present on the 2100 with the 2000 screen
(which was perfect). Therefore, no amount of resetting will do anyhting -
it's a hardware problem with the screen.
I measured the resistance across the four terminals of the touch screen and
it's not sensitive to pen strokes at the edges of the screen so pressure
from the bezel is unlikely to make any difference or be the cause of the
Looking at the change of resistance across the screen as the pen tracks
across it, the change is very uniform in all areas (between 750 ohms and
1.4k ohms) except in the bottom right of the screen where the resistance
dips when it should be at its maximum value. This is just the place where
you tap the pen alignment cross. On my machine this also corresponds to the
micro-damage to the screen surface.
So it looks like something has affected the performance of the touch sensor
in this area (heat, abrasion, pressure, chemistry?) which may, or may not be
The clue will be in how, and in what environment the machines were used.
I'm really sorry that the conclusion is that if your machine has this
problem the only solution is to swap it for another screen unless someone
knows an expert in touch screen engineering who can suggest alternatives.
Whatever, don't dispose of good motherboards for a bad screen, they are
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