Texas Instruments TI 57 Programmable Calculator 9V Battery Back

This is an upgraded back for the TI Programmable 57 calculator.  With an original MSRP of $40 in 1977 (over $200 in 2022 equivalent buying power), the TI Programmable 57 calculator was designed to use 2x NiMH 1.5V batteries connected in series with a boost converter to create 9V output to run the calculator.  Now - 45 years later - The battery packs in these calculators have almost all leaked some nasty acid and no longer do their jobs.  And even if the rechargeable batteries did work, the battery pack required a charger that has typically not survived.

Fortunately, 9V is easy to find in common batteries.  Less fortunately, these batteries require a little bit of re-wiring for them to connect to the existing calculator wires properly.  The Texas Instruments engineers in 1977 decided to reverse the wire polarity colors; meaning the calculator's + wire is black and the - wire is red.  Normally this would be a simple annoyance, however the connector that comes with the calculator is NOT polarized (it's a simple DuPont connector), so plugging the battery in backwards is a real possibility.  

Here's a lot more writing about upgrading this particular calculator by Simon Monk (not me): http://www.doctormonk.com/2014/06/ti-programmable-57-calculator-battery.html

I decided on my example to remove the DuPont connector and install a normal 2.54mm 2-position JST connector.  Creating a matching harness with a PP3 connector assembly will prevent a reversal of polarity to the device and stop me from doing more damage than has already been done in 45 years of life.

Once the PP3 wire leads are properly trimmed and the JST connectors are properly installed and wired simply hook up the 9V battery to the connector, snap into place in this redesigned back, and enjoy that sweet NERD CRED™ wielding your new/old toy wherever your vintage calculating needs may arise.  Pairs perfectly with a slide rule if you want to confuse the younger engineers.

For printing, I recommend using a resin printer, but FDM works pretty well too. Print this in the default orientation with 3 walls, 100% infill, and 0.1mm layer heights.  The battery does actually snap into place, so support the few overhangs at least a little bit so things don't get too wonky.  FDM supports “everywhere” is recommended.  Make sure you have the correct floor/roof settings and offsets.