My TI-89 Titanium developed a tiny spot that was always blue (rather than the greenish color of the background or the dark gray color of the foreground) regardless of whether it was on or off. Over a period of weeks, this spot started slowly growing to encompass more area (a few pixels wide & several pixels tall at its largest extent). I have seen a similar effect in other screens & had always assumed it was irreversible, but it appears that it is in fact reversible (or at least, was in this case).
Disclaimer: I am not responsible for you choosing to follow anything described herein, nor for the results of such actions. I have only tried this once with a single calculator (& even then, I prayed about it beforehand), so it may not work on any other model or even other calculators of the same model.
LifeEmu had mentioned in chat that he had the same thing happen with a different model of calculator & had tried cooling it, which had made it spread much faster. I therefore reasoned that perhaps heating it would cause the spot to retreat instead. But I did not want it to heat too quickly & damage anything else (especially the LCD ribbon cables, which have been known to dry out & detach), so I ended up putting it behind my desktop's exhaust fan while having it busy for a few hours (power usage around 120 W, in case anyone wants to attempt to match the amount of heating). This reduced the size of the spot but did not completely eliminate it, & it started to grow again after left at room temperature overnight. Then I left it in the heat until the spot completely disappeared, after which it has not returned in a bit over 5 days. (I cannot guarantee it will never return, nor—again—that it would work on any other calculator.)
Everything else seems to still work properly, except some of the keys might be occasionally not registering when they were not before, so it is possible that the heat damaged the keypad. (It is also possible that I was pressing them differently, or that the keypad sustained damage from an unrelated source, or that there was no change & I only noticed because I was looking for problems.)
Disclaimer: I am not responsible for you choosing to follow anything described herein, nor for the results of such actions. I have only tried this once with a single calculator (& even then, I prayed about it beforehand), so it may not work on any other model or even other calculators of the same model.
LifeEmu had mentioned in chat that he had the same thing happen with a different model of calculator & had tried cooling it, which had made it spread much faster. I therefore reasoned that perhaps heating it would cause the spot to retreat instead. But I did not want it to heat too quickly & damage anything else (especially the LCD ribbon cables, which have been known to dry out & detach), so I ended up putting it behind my desktop's exhaust fan while having it busy for a few hours (power usage around 120 W, in case anyone wants to attempt to match the amount of heating). This reduced the size of the spot but did not completely eliminate it, & it started to grow again after left at room temperature overnight. Then I left it in the heat until the spot completely disappeared, after which it has not returned in a bit over 5 days. (I cannot guarantee it will never return, nor—again—that it would work on any other calculator.)
Everything else seems to still work properly, except some of the keys might be occasionally not registering when they were not before, so it is possible that the heat damaged the keypad. (It is also possible that I was pressing them differently, or that the keypad sustained damage from an unrelated source, or that there was no change & I only noticed because I was looking for problems.)
