Question from the dark side ;-)

[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