A design error in the support for the battery terminals can
cause the thin plastic wall of the terminal to give way
due to pressure from the inserted batteries. When this happens
the battery loses contact and the calculator malfunction. A simple repair
is to place a strip of nylon tubing to reinforce the battery terminal wall.
The moulded model number on the case is S-2 but this
is covered over with a label showing the calculator as a S-1.