TI-58C not powering up

[Maximilian Hohmann]

Hello!

If the battery is totally dead it can absorb all the power that it gets from the charger with nothing left to power the calculator.

This series of calculators from Ti can safely be powered from their charger without a battery in place (other than the notoriuos "Woodstocks" from HP). It may not be working properly because the battery is required to stabilise the voltage, but at least you should see the display coming on and get some response from the keyboard.

The safest option would be to remove the battery and connect the contact srprings to a regulated (laboratory) power supply using crocodile clips. Set the voltage to 3.6V DC and mind the polarity. Which is not difficult because contrary to HP - and I say this to our members here who enjoy bashing Ti :-) - Texas Instruments undertook the effort to put polarity labels next to the battery connectors!

Replaycing the charger is not so easy. There are quite a few different ones depending of the year of manufacture of the calculator (Datamath has the full list here: http://www.datamath.org/AC_List.htm) but they all have in common that they output AC voltage and have a proprietary plug to connect with the calculator. So if indeed your charger is broken, forum classifieds and eBay will be the places to look for a replacement. By the way: The ones that came with the calculators originally in Europe (I have several and they are all identical) are completely sealed and have no fuse. They either work or have a burned out transformer.

Good luck with your repair, it's a pretty calculator well worth being brought back to life again!

Max

NB: If your calculator still works it might be an option to replace the NiCd cells with more modern Lithium cells as described in this Hackaday article: https://hackaday.io/project/176529-ti-59...ttery-pack