HP48GX RAM card design

[wan]

(01-21-2021 06:27 AM)Marco Polo Wrote:  How you manage to change the battery? It should be changed with card installed in calculator, if I remember correctly, in order to avoid memory clear.
In the original design the battery is located on top side (the one accessible when card is installed ). Cynox design is similar.

There‘re two gold colored capacitors on the bottom right of the board, these two 440uf capacitors will provide power when changing the battery. They are larger than Paul's original design and provide longer holding time. I think they can hold for more than 20 seconds.

The reason for not placing the batteryholder on top is to avoid touching it when pulling the card out. Pulling the card with batteryholder will apply shear force on it, which may cause the batteryholder to desolder over time.