Dark patch growing in LCD screen

[Ender]

I have a HP42S that I seldom use. It came to my notice that that there's a dark patch in the middle of the LCD that gets bigger with time. Presently, the dark patch which is elliptical in shape nearly covers the entire screen save the two ends. Other than that the calculator is working fine. Did anyone have the same experience what what did you do to resolve the problem? Thanks.

[ijabbott]

The fix would require opening the calculator up and replacing the reflective backing on the LCD. There is a thread covering this process for a HP-22S: https://www.hpmuseum.org/forum/thread-12652.html

An alternative would be to replace the entire LCD module using a HP-17B or HP-17BII (but not a HP-17BII+) as a donor. (I'm not sure about the 17BII+, but since it is a reimplementation of the HP-17BII, I'm guessing the LCD module would be different.)

[Ender]

Ian Abbott,
Thanks for the prompt response. The link you posted is most useful.