HP31E Missing Pin

[ThomasF]

(03-14-2021 07:42 AM)teenix Wrote:  I assume 3V will do. Do you know what polarity the battery terminals are? The battery terminals are on about a 25 degree angle on the small pcb, do you know if the upmost is +ve or -ve?

Hi Tony!

The - is closest to the top of the calculator, and + "downwards" to the bottom.
Check this picture:
https://www.hpmuseum.org/batts/bc30.jpg
Ref: https://www.hpmuseum.org/cgi-sys/cgiwrap...read=49445

Cheers,
Thomas