Dim LCD display on old Casio calc

[spanakop]

Hi all. I have an old Casio fx-7000GB calculator (I love these old Casio's), where the display is quite dim. Even when I adjust the contrast, it still need to tilt the calculator at an angle before I can see a decent display. The batteries are good, all the functions are working, there are no inoperative buttons, just the dim display.

Is there anyway to fix this problem, or is it just a worn display (if there is such a thing)?

[Gyro]

It's probably contamination or ageing (compression) of the conductive rubber 'zebra strip' that connects the LCD to the calculator PCB (forum search zebra strip to get a better ideas and probably some images).

The question is whether you can get the calculator case apart without damaging it, it depends whether you want to maintain it in perfect cosmetic or best working condition..

You can usually clean up the PCB pads, strip and edge of the display with a little IPA - checking under a magnifier that you don't leave any paper or fabric fibres on the contact surfaces.

[Haenk]

As this was one of my first calculators to own, I can confirm that the display has always been awful.
Those cheap LCDs will get even worse over time though, probably through chemical aging, however there are no replacement parts available (of course) and if I remember correctly, the zebra strips are bonded to the display and PCB. (Which also means no fixable contact issues...)
Putting your lighting at the right angly is the best way to use it (and has been back then).

[spanakop]

Thanks guys. As I'm not seeing any missing segments or lines in the display and the problem is display wide not in specific areas, so I'm less inclined to think it's a bad connection.

My 'fix' is to angle the calculator at an angle to see what's going on more clearly, as Haenk mentioned. Interesting to know that this was a problem when it came out originally.

I'll open it up this weekend and have a look inside. It's not my main calculator anyway, I have another eight calcualtors to use if I need to, a mix of old a new (I even have an old slide rule).