It was only after 37 (!) years of service that my vintage Texas Instruments TI-58 programmable pocket calculator stopped working. Actually, the calculator was still fine but one of its original NiCd batteries had finally passed away.
My TI-58 has always been ‘my precious’. Its (by modern standards) limited memory size inspired me to design smart algorithms and to write efficient programs.
This was, however, a very powerful calculator in his days. A special version was built into the famous Harrier aircraft to perform all calculations needed for stabilizing the airplane during vertical takeoff and landing!
Although the NiCd batteries were standard AA type, they turned out to be sealed inside the battery cover and had spot welded contact strips. So some minor surgery was needed in order to replace them with a set of fresh 1900 mAh NiCds.
This shows the battery module before and after the operation. The tape was just a helping hand during surgery that I forgot to remove (happens in hospitals too).
And there she is, my reborn baby, proudly showing her purchase date.
And finally she got reunited with the rest of the package.