HP 19bii Problem with the screen

[Maximilian Hohmann]

(09-05-2018 07:20 AM)math7 Wrote:  Does anyone know why a stain is made like this and how could it be removed?

Guessing from the photos to me it looks like the residue of some liquid, maybe just condensed water, trapped either between the LCD and the protective layer of clear plastic, or between the glass of the LCD and the polarising filter.

In any case the calculator would need to be disassembled to clean it out which is not an easy thing to do and which carries a big risk of inflicting major damage.

If you are very lucky the stain was caused by someone who cleaned the screen with some kind of solvent and left it to dry in a puddle instead of wiping it off. In that case it might be possible to even it out somewhat with more solvent (start with "gentle" ones like alcohol and lighter fuel before moving to hard stuff like paint thinner and acetone!). Or try to polish it out with a mild polishing paste like "PolyWatch". I wouldn't waste to much time on it, these calculators are in plentiful supply and not as expensive as others from HP. I bought one a couple of weeks ago in near mint condition for 10 Euros.

Regards
Max