Fwd: My Ultralite

Eli Brian Goldberg (eg1n+@andrew.cmu.edu)
Mon, 9 Dec 1991 13:12:40 -0500 (EST)

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To: Eli Brian Goldberg <eg1n+@andrew.cmu.edu>
In-Reply-To: Eli Brian Goldberg's message of Sun, 8 Dec 1991 18:09:34 -0500 (EST) <gdEeMi_00WB3M=4UZt@andrew.cmu.edu>
Subject: My Ultralite

Youch! That sounds like what happens when an LCD display is driven with
DC rather than AC. The pixels of an LCD display are normally flipped
between several different states at a fast rate -- the relative time spent in
each state determines the intensity of the pixel. If a pixel is driven to
a single state for more than a few seconds, then it will get "stuck" in
that state. This can cause permanent damage. If this is the problem, then
you want to try leaving the screen on with the contrast knob in the
normal position -- the bars will fade out if the screen has not been
damaged. I cranked the contrast over on my UL and am not noticing any drive
problem so I suspect you may have some other hardware defect -- a problem
with the power supply for the LCD or its driver chips could easily cause
the kind of problem you are seeing. Perhaps the problem is as simple as
a defect in the contrast control such that it produces a bogus drive
voltage at the right end -- the contrast control generally tweaks the
bias voltages of the LCD's drivers.

Good luck,

Bob Armstrong (rca@rle-vlsi.mit.edu)