The "1" key did not work. I tried pressing hard and tried resetting the calculator, neither of which worked. I therefore disassembled the calculator to see if there was a bad connection of some sort. Once I disassembled the calculator I pressed directly on the key contact for the "1" and it worked. I therefore reassembled the calculator. Unfortunately, the %key was not fully seated and came out. Also, once I was done the mixed number key did not work. I do not know if this is a new problem or not. I will therefore probably again remove the 24+ screws to see if I can get the calculator fully working. At least it is usuable now.
After opening the case.
Card with processor lifts up.
Board with key contacts connected to processor board connected to display.
Processor board and board with key contacts turned over. Underside of keys also shown.
Close up of board with key contacts.
Other view showing underside of keys, other side of processor board and ribbon connecting processor and key contacts.
The left over % key and four screws. (Two of the screws go in the battery compartment.)