TI-58 Calculator battery upgrade

After a weekend at Minicon I came back with plenty of goodies thanks to the trusting nature of Amtrak (look for a CDV-715 post coming up) and one of the smallest was this TI Programmable 58 calculator.

original

I love old bubble display calculators, thermostats, stopwatches, whatever I can get my hands on.

crusty

This repair seemed pretty simple, replace the old Ni-Cd batteries with new ones.  The challenging part was someone already did this once before.

you’ve had some cowboys in here…

The batteries were a snug fit, the power tabs snapped, and I ran out of patience.  The original TI charger for this was rated to put out ~3v although after the bridge rectifier easily identified was somewhere around 6V DC-ish.

looks like a rectifier, that can go

I decided that that’s close enough to 5 for 1977 and injected my new power source there.  My selection was based on what I had lying around which turned out to be a micro-usb lithium charger/boost converter that put out 5 volts and a lithium battery out of an old ipod external battery pack from radioshack long ago (I bought it before the advent of common charger/boost converters for single lithium cells).

all kapton’d up

Put together and with some kapton to hold it in place and a dremel to hollow out the case I successfully added usb rechargability to this old calculator.  I will admit that it is now incompatible with some of the add-ons, but I’m not terribly concerned as I intend to use it just as a pocket calculator.  All pictures (including others not in this post) are here.

useful once again

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