This is my attempt at repairing my old trusty calculator that had developed an unresponsive keypad. I really like mashing the keys when calculating stuff quickly at work and it is awesome at getting quick calculations done in a rush. Hopefully I can repair it and use it for many more years to come.
The calculator came with an alkaline backup battery to help it work when the light is dim. While it is a nice touch, it also risks leaking and corroding the delicate circuit board traces inside. I might continue to use it without the battery since the solar panel actually works very well under office lighting.
In this case, I managed to solve the issue by cleaning up the battery leakage using isopropyl alcohol around the battery area.
Hope this view helps if you encounter unresponsive or unstable keypad issues. Cheers!