[sdiy] Why do LCDs die?

[Tim Parkhurst]

So, I have an old Roland U-220 that I haven't used in a few years, but I
keep it around because I do love the piano and string samples. The fretless
bass and the drums are pretty good too. Also, I'd be lucky to get $50 for
it these days. Long story short, I turned it on the other day and the LCD
was barely visible, getting dimmer to the point after a few hours where it
is completely unreadable. The backlight is okay, but the digits themselves
can't be seen. I see there are replacements on the market, so I should be
able to resurrect it, but this begs my original point:

What causes LCDs to die in the first place? Are the crystals themselves
unstable? Is it the high-frequency excitation required that causes an
eventual breakdown? Or is it mechanical, with small connections or wire
bonds breaking down with time? Do we replace them because they are
unrepairable, or is it simply a matter of replacement being quicker and
cheaper than repair? Is there an internal adjustment to crank up the
contrast on this old beast (can't change the contrast from the front panel
settings since I can't see the display to navigate)?

Awaiting the collective enlightenment from the SDIY hive mind...

Tim (do Borgs get hive mind hives?) Servo
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