Question from the dark side ;-)

[JurgenRo]

So, I've to admit that - apart from my trusty HP-41 and other HP calcs - I do own a few TI calcs as well. Among those a nice TI-58C which I tried to power on recently. When I turn on the machine (charger pluggeg, w/ or w/o batteries) the machine would turn on but it seems to hang in a running/computing state. That means, that there is constantly a "C" in the left of the Display while the display is very actively running numbers. Moreover, the calc does not respond to any key-press. Does anyone know what could be wrong with this machine? Thanks a lot!

Juergen

[jebem]

These machines should never be operated using the external charger connected without having a good working battery in place.
The battery acts as a regulator device to make sure sensitive components, like the SRAM ic`s, will not receive an unregulated high voltage at their power supply terminals, most probably killing the chips.
See here more details.

[Maximilian Hohmann]

Hello!

From my more active Ti days (I mostly used a Ti59 for many years) I remember that the condition you describe could be invoked by removing the battery pack and re-inserting it loosely. If you then switch on the calculator and tap lightly on the table, a brief interruption of power will send it into this "endless stopwatch mode". We did this at school during boring math lessons...

So I guess that either your power supply is not stable enough, the battery is poorly connected, maybe due to corroded contacts, or one or more battery cells are defectice. I guess that also a bouncing on/off switch could cause brief voltage interruptions while turning on the calculator.

The battery itself is part of the power supply circuit, it acts as some kind of large capacitor to stabilise and even the voltage. Connecting the calculator to the mains without a battery inserted (or with a totally dead or internally disconneced battery) usually results in erratic displays as well.

I would suggest to connect the calculator to a regulated DC supply set at 4V, not via the charging socket, but directly with crimps to the battery contacts (watch the polarity, the negative is the one at the top end of the calculator). If it still does not work, it is either the power switch or (just guessing now) a defective component in the power circuitry. If you happen to have access to a PC100 printer, you can also use that as power supply.

In my experience, calculators from Ti are very robust, especially as far as power supply is concerned. I have very few in my collection that don't work. Their real weak point is the bouncy keyboard.

Regards
Max

[JurgenRo]

Thank you both very much for your Inputs! I have a rebuild battery pack that I use with my TI-58/59, so I don't think that it is a battery Problem. I've to admit that I tried for comparison reason to drive it w/o batteries - identical behavior. Well, I'm aware of the danger to do so. On the other Hand, I never burned a TI-calc that way. You are absolutely right with your warning anyway!

Will definitely try to drive it with regulated DC supply set at 4V! Thank you again!

Regards,
Juergen

[JurgenRo]

Success! You were all right! It does work, the battery just needed a base Charge! Calculator passed self-test ok :-) Thank you so much again for your Expertise!

All the best,
Juergen