HP-25 display weirdness



I have revived my old 1976-vintage HP-25 from my university days. I have replaced the NiCads with new ones, connected by short wires soldered to the PCB so as to avoid contact problems.

It seems to work fine, except that the decimal points in the display light up as if the low battery warning has come on, even though the batteries are fully charged. Also if I press e.g. 2222 Enter, the last 2 in the display has the bottom right-hand segment faintly lit.

Any idea what causes this? Also, what is the little trimpot on the mainboard just beneath the display for? Turning it doesn't appear to do anything.

Thanks for any suggestions.

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