Troubles & Repair of the TI-59

Working on the TI’s. So I’m happily living right along in my life – what with my stable of vintage Texas Instruments TI programmable calcs – and I take them out to charge up the battery packs and generally just play around with them, the TI-57, TI-58, & TI-59 along with the PC100A printer cradle. I charged up the 58 & 59’s battery packs and was playing around with the 58 off the cradle and with it on battery power, when the display slowly faded. I’d only been using it on battery power for a few minutes. I quickly switched out the 58’s battery pack with the 59’s and was back in business. Five minutes later the display faded out once more. Well, it was all good while it lasted.

 

Apparently these two calcs with their battery packs have sat for over 30 years without a charge and since I’ve owned them and charged them, oh, maybe a half dozen times – that must have done them in. Well, even eBay’s going rate is $40. for a replacement battery pack that’ll fit. Same pack fits either unit. It’s just a plastic box with 3 NI-CD’s fitted. It’s a custom case though and to replace the batteries you need to kind of cut the battery case open and separate the metal contacts then solder some leads to connect the batteries and then sort of glue the case back together. So, basically the $40. is because it’s a bit labor intensive. Well, I’m giving a go to doing my own rebuild rather than paying $40. to someone else for basically $10. worth of batteries.

In replacing my 34 year old battery pack with new NiCd batteries I followed instruction pictures I found on the Internet and cut the case as shown. You can see why the battery pack was not holding a charge anymore because the batteries were starting to leak. It’s funny that they took 34 years to get to this point. I’ll bet they didn’t start to corrode until I started charging them up after they’d sat so many years. Now I need to go buy some batteries, but the repair article stated to get a phone battery pack with solder tabs – and the only place you’ll come up with that type is on the Internet. In the mean time I’ve fashioned just a 3.6v phone battery I had sitting around. Most phone batt. packs have a plug like the one I am using in the TI-59 now.

Then I decided that since that was working pretty well except I had no battery compartment door now. The original battery pack is built right into the door. So, I modified the battery holder slightly so it would hold the phone battery I’m already using. Now I have the battery inside and the compartment door closes just fine. - -

Well, it did until I wanted to take a nice picture of my handy work, and I messed it up. I broke the locking tab and now I have to put a piece of scotch tape on the door to hold it closed. Bummer. I hate plastic tabs, they break too easily!

Anyway, I did get the picture showing how I’ve moved the wires inside and how I can still hook the TI to the printer, (if I can figure out why now the TI-59 doesn’t want to work when hooked to the printer!) It works fine off the battery pack though. That’s another ‘thing’ to try to fix. Also when I get my new battery pack done – it can replace the phone battery without having to change a thing. Just move the wires away and tape the ends inside.

Here’s the back closed now –

and I’ve replaced the unsightly clear tape with black electrical tape so it’s barely noticeable. I have another battery pack that I will be more careful with when I rebuilt it and I think I’ll just regulate that to the TI-58 and use the TI-59 this way for now. At least until I can figure out the problem with it not working on the printer cradle. I took it all apart even and could see no reason for it’s not working on the cradle. All it has to do is make contact with the two tabs and that it did – but still wasn’t getting any power. Go figure?