HP 37E - Battery charging issue

[Dieter]

(11-12-2017 07:10 AM)johnlyles Wrote:  ...but after using the calculator for several hours, when I connect the charger to verify that the battery pack will charge normally, nothing seems to happen. Is there visual means of knowing if the battery pack is charging??

I cannot say much about the calculator's internals, but here is a first test that may help: Simply run the 37E until the low battery annunciator comes on. That's a red dot in the upper left corner of the display, in the leftmost segment, right above the minus sign of a negative number (which then appears like the upper half of a "÷" sign). You may run a program to discharge the batteries faster. After the red dot has appeared, plug in the AC adapter. Within a few seconds the dot should disappear, indicating that the voltage has come back to normal. This way you can at least detect if the adapter correctly connects to the calculator. Which does not neccessarily mean that it also charges the battery pack. ;-)

In order to check if the adapter's output actually reaches the battery you may simply connect a multimeter to the two battery contacts and see if the voltage rises if the adapter is plugged in. You might insert two thin metal strips (e.g. folded aluminum foil) between the calculator's contacts and the battery for better access with the probe tips.

Dieter