Reviving Your TI-59 Calculator

Ed Grochowski

Introduction

In 1977, Texas Instruments introduced the TI Programmable 59. With up to 960 program steps and 100 data memories, the TI-59 was the flagship of TI's calculator line at the height of the 1970s calculator era. The TI-59 remained in production until 1983. Although Texas Instruments went on to create newer models, the market for powerful and expensive programmable calculators had largely disappeared with the advent of the personal computer. Today the TI-59 is a valuable collector's item.

My parents purchased a TI-59 calculator for me at Christmas 1977. I learned a lot about programming and mathematics using this calculator. My TI-59 served me well through high school and college, but by the late 1980s, had fallen into disuse.

Battery Pack

An obstacle to keeping the TI-59 alive is the battery pack. The calculator is powered by a three-cell NiCd battery pack (BP-1A). The battery pack is an integral part of the calculator's power supply; the calculator cannot be used without it. The life expectancy of the battery pack is 5-10 years. After that, the battery pack will leak and must be discarded.

Since the BP-1A is no longer in production, the TI-59 owner has two options: rebuild an existing battery pack with new cells, or eliminate the battery pack and adapt the calculator for AC line power. I restored my TI-59 using the latter approach.

Regulated DC Adapter

The TI-59 may be powered by a regulated 5VDC, 500mA adapter available from Jameco Electronics. Replace the adapter's plug with a standard 0.1 inch 2-pin female connector. The polarity does not matter. The 5VDC output of the adapter is reduced to the nominal operating voltage of 3.6V by the diode bridge in the calculator.

The opening for the battery pack may be covered by a small piece of plastic from a 3.5 inch floppy disk. Disassemble the floppy disk, use a nibbling tool to cut the plastic, file, and glue in place.

The regulated DC adapter must not be used with a battery pack installed.

Conclusion

With the regulated DC adapter, the calculator will operate without periodic battery replacement. My TI-59 is once again working. Happy 25th anniversary, TI-59!