> >>> If you can't get anything at all on the screen you may have one of
> >>> the high-temperature modules which requires more than 5V of LCD
> >>> drive.  In that case the LCD drive pin needs to be pulled negative
> >a
> >>> few volts.
> >
> >> But that would guarantee that a normal temp one would loose its
> >> smoke....
> I don't think it would, the only difference is likely the LCD panel
> itself (the chips are rated for high voltage).  So all pixels in the
> panel would go completely black, holding the voltage that high for a long
> time may burn it.  This test is only if you can't see anything at the
> regular voltage anyway.

Running a display with somewhat excessive drive voltage may cause long term
damage to the "dark" pixels, but displays are remarkably hardy when it comes
to AC voltage (a large DC voltage, on the other hand, can destroy a display
quickly and even a fairly small one can destroy it slowly).  A friend of
mine told me he saw a company revitalize some custom LCD's that had some
internal shorts (the legends were so small that some of the conductive
material flaked and bridged) by connecting the displays (with the driver
chips REMOVED!) to raw AC120.  The shorts were instantly burned off, leaving
the rest of the display functional.  According to my friend, the batch of
displays had only about 15% yield off the factory floor, but almost all of
the "bad" displays were revitalized with this technique.

BTW, on a somewhat related note, it's important on some LCD's to be careful
of what data are used to drive them.  While some LCD drivers reverse the
driving polarity on each scan line, others reverse it each frame.  If a
pixel is driven dark on "even" frames and clear on "odd" frames (or vice
versa) this can then produce a DC bias that can wreak havoc on the display.

Once upon a time, I ran into this phenomenon first hand (quite a rude
shock, as it happened); I was programming a laptop computer with an active
matrix color LCD (back when the display alone on one of those things cost
more than my car) and left the display running a program that flashed much
of the display between two colors while I went to lunch (having no clue
that this would be a bad thing).  When I came back from lunch (about 1/2
hour) the part of the display that had been flashing was very badly and
wierdly "fogged"; as I worked with the computer for the next few hours the
fogging largely subsided, but signs of it persisted until the next morning.
Had the display been in that state longer, I suspect it might not have rec-
overed so well.

[btw, I don't know if current laptops do anything to prevent this problem;
alternating polarity on even/odd scan lines might have helped since any
leakage between lines would help bleed off any accumulating charge]