HP 65 with capacitor wired to battery terminals - why?

[Dave Britten]

(07-19-2021 03:18 PM)Ren Wrote:  For whatever reason, I was unable to view the picture.
My SWAG is the previous owner had a lot of noise on their power grid, or maybe the power supply they had was weak and so the capacitor provided enough power for intermediate demands of the calcs.

I bet it's something like that. These calculators aren't supposed to be run without a good battery, as it acts as a regulator. This looks like someone stuck a cap in there to run it off wall power with no battery. Maybe the previous owner wasn't impressed with battery runtime and wanted to run it purely from external power? No idea if it's safe to do that with a big cap instead of a battery!