Texas TI-59: A tale in pictures

[jebem]

The Battery issue


The original battery using NiCd technology was designed to survive a few charging cycles (500 to 1000) using a basic charger circuit.

By replacing it with different NiMH cell technology battery soldered directly to the calculator battery terminals, meaning that it will be charged by the original calculator built in basic charger circuit (a resistor that is out of circuit when the calculator is powered on, meaning that the full charger current is applied to the battery), one can only expect the worst.




The wrong NiMH cells used for a while in the calculator. Battery leads soldered to the PCB terminals.




After cleaning. But it was to late for the keyboard domes.