How to open a Casio FX-4000P?

[grsbanks]

(08-08-2021 12:30 PM)johanw Wrote:  I didn't even have to tune up the contrast (is that even possible on a 4000? I didn't see any keys for that) as was the case with my FX-8000G, when I replaced the batteries in that one my heart sank when I didn't see anything when I switched it on, until I got the idea to push up the contrast. That worked.

I often found that replacing the batteries left all kinds of corrupt data in the 6000/6500/7000/80000/8500G series, including barely visible contrast. On those machines at least it's always a good idea to press the Reset button on the back, and more often than not, that rectifies the poor contrast.