Powerbook 160 contrast slider cleaning

[Shaddam IV]

Hello, I have a Powerbook 160 on which it is very difficult to set the contrast properly. The range where the contrast slider actually changes the contrast is very narrow - when I move the slider to the centre position, I can move it maybe 3 mm at most to the left or right before the picture becomes too dark or too bright. I would like to clean the slider and hope that things will improve. How do I do that? Thank you! Kind regards, Karl