Posts: 883
Threads: 17
Joined: Feb 2006
Don't bother to open it, it will not help in any way, you can't clean it from the back. Check all your keys for any loose and wobbly ones, especially the "/" key. If it is loose and wobbles side to side, put the calculator on a shelf and buy a replacement as you will not be repairing it. The divide key has a broken hinge and it has divided one too many arguments on the stack.
If the keys are all nice and tight, take the batteries out and place several drops of isopropyl alcohol around the "/" key so that it seeps down into the keyboard and press the key several times. Repeat with a few more drops. Let it dry for a while, 15 minutes or so. Put the batteries back in a give it a try. If you have the same problem you might well have an SX keyboard that has reached end of life.
If you have access to an ultrasonic cleaner you might give that a chance if the easy method doesn't work.