HP-33C strange power / weak battery indicator problem

[teenix]

The battery low LED is controlled by an internal voltage monitor circuit built into display module and monitors the battery voltage when the calculator is switched on.

The LED goes on/off at around 2.18 - 2.20 battery voltage.

There could be a drop in voltage anywhere from the battery and connections to the power board and then through the CPU board and then to the display. These connections are not soldered so there could be a higher than normal resistance join. The battery connector and ribbon cable connection is rivetted and may be high resistance also especially if there are signs of corrosion.

The battery is monitored via the outer most pins either side of the display.

cheers

Tony