Can TI SR-5x and TI-5x be run from AC with no battery?

[brouhaha]

Is it safe to run the TI SR-50/51/51A/52/56 and TI-58/58C/59 calculators from AC with no battery? Or do they have the design flaw of the HP Woodstock series, where the battery is necessary to limit the voltage and avoid damaging the PMOS chips?

[Maximilian Hohmann]

Hello!

(03-23-2023 09:20 PM)brouhaha Wrote:  Is it safe to run the TI SR-50/51/51A/52/56 and TI-58/58C/59 calculators from AC with no battery? Or do they have the design flaw of the HP Woodstock series, where the battery is necessary to limit the voltage and avoid damaging the PMOS chips?

Just today I received a Ti SR-10 in the mail (the first "scientific" calculator from Ti from 1972) and the manual explicitely warns against powering it with the wall charger when no battery is in place, otherwise "damage may occur".

In the past I did occasionally power my Ti59 without a battery and it just wouldn't work properly. The display flickers and the card reader can't read cards. So far these attempts did not damage the calculator permanently, but I will never try it again.

If you have no (working) battery the safest way to power these calculators is a PC-100 printer. Different form the wall charger, it supplies a regulated voltage.

Regards
Max

[brouhaha]

(03-23-2023 10:09 PM)Maximilian Hohmann Wrote:  If you have no (working) battery the safest way to power these calculators is a PC-100 printer. Different form the wall charger, it supplies a regulated voltage.

Thanks for the info!

I do have a PC-100A, and a newly made BP-1A replacement, but I wanted to use the AC-9130 wall wart with the SR-5x calculators, because most of the SR-5x calculators I've been given have broken battery contacts.

[Mark]

Hi,

Here's an alternative to the original charger, successfully tested on a TI-58 :

You can safely power it without batteries, by connecting a regulated 5V DC source to the charger terminals.
Either polarity will work : The 1.2V dropout induced by the built-in bridge rectifier will result in 3.8V on the battery terminals, the 200mV increase versus the nominal 3.6V won't harm anything as far as I know.

That should also work for the SR-56 which includes the same bridge rectifier (not sure about the other models).

Regards,
Marc