On Thursday, February 16, 2017 at 12:00:25 AM UTC-5, isw wrote:
I have a La Crosse Time-Temperature device that I picked up at a garage
sale about a year ago. It had a badly corroded battery compartment,
which I got cleaned up, at which point the thing started working.

Recently, the display (it's one of those "big number" 7-bar LCDs) has
gone quite dim when viewed head-on, but is plenty contrasty viewed at a
large vertical angle. It did not have this problem when I first got it.

I know the most likely reason for that is a weak battery, but the cells
checked out at about 1.5 V and replacing them made no difference.

La Crosse claims to have no schematics or other technical data at all
("the clock is made entirely in China").

Devices often have a "contrast" adjustment which changes some bias on
the LCD and alters the best viewing angle, but this particular unit does
not offer that as a user adjustment.

Is there some way that I can identify the particular connection to the
LCD which provides this bias? If I could find it, I bet I could hack it.

thx

Isaac

Take another look inside the device. Battery spew tends to migrate away from the point of egress, and it might not be visible. A tiny bit of stray conductance could throw the display off. The board might benefit from a good soak.