How to repair the Texas Instruments BP-1 battery pack* (see disclaimer below).
|Use a coins to open the battery door. Check the internal circuit for battery leckages and clean the calculator. If you find broken battery contacts you have to repair-it using metal spring and soldering iron. You can check the calculator with any external 4.5V DC stabilized (or external battery) power source connected to the contacts (use two cables with crocodiles contacts). Carefully respect the polarity: external contact is negative, internal positive (you will see the + and - mark on the circuit board).|
|Ni-cd battery lose the ability to take charge after 500/1000 charge/discharge cycles, but the battery pack life is usually shorter due to common misuse: total discharge (pack is damaged if not charged for months or years) or overcharging. With the original Texas Instruments BP-1 battery pack dead the calculator became unusable, also when the power adapter is connected. The reason is simple: dead battery short the charger or act as open circuit making the adapter current unstable and potentially dangerous for the electronics. The solutions is simple: you have to rebuild the battery using three standard low-cost ni-cd elements.|
Disassemble the battery using a small screw. Break the glued plastic column and extract the batteries. Disconnect the two metal finger from the battery. Save the terminals long as it's possible. Clean the finger from corrosion and use tool to reshape the metal. Dispose proprely the battery: nickel pollute the environment.
|Use adesive foam and copper strip to create electric connection between the three standard ni-cd AA cell. The idea is to use the original plastic shell as standard battery holder. Cell are connected series by the copper strip.|
||Reassemble the plastic columns in their position with the metal bar (use glue or double side film between metal fingers and plastic). You shoud be able to place the two free battery terminals connected with the two metal fingers.|
|Use adesive film to take in place the plastic columns and the battery. Before use check carefully the polarity: + should be close to the opening slot (if you made mistake you can destroy both your calculator and the battery). Insert the battery pack, connect the charger. After few minutes switch on the calculator and check. If you see unstable blinking display switch off the calculator and check the battery pack and calculator springs for bad contacts. If ok recharge your battery overnight. Remember: the standard charging time proportionally increase if your battery have more than the 450/500 mA original capacity.|
(*) Disclaimer: We offer this repair experience as it is, without any warranty about contents or results (results depends by your personal ability, electronic knowledge and also lucky). Use this information at your risk: we are not responsable for injury or damages eventually caused.
back next home mail