About AC adapters
There is a variety of AC adapters made for different calculators. Always make sure that you use the matching model. Color-coded and keyed connectors make it
easy. See the table in the Datamath Museum.
Never use replacement adapters from retail stores. Never! Why?
When it comes to charging, some characteristics of the adapter you may have never considered become vital for reliable operation of the Battery Pack circuit.
From the TL496 schematic,
you can see that only the internal resistance of the transformer limits charging current. Texas Instruments adapters have quite high internal resistance, many retail models have not. Using such a model can easily
... and don’t miss this!
As the battery pack circuit is powered on all the time, it regularly compensates output voltage droop caused by capacitor leakage current. Thus, the voltage
converter is switched on for a short period of time once every few seconds.
Want to prove this? Take an AM radio receiver and de-tune it
(so you only hear low noise). Then, put the battery pack on top of the receiver, near the antenna location. You will hear a ticking sound ... the battery pack lives!