Reviving Your TI-59 Calculator
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.
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.
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!