Replacement of the BP7, BP8 and BP9 printed circuit board

The small printed circuit board (PCB) found inside the BP7, BP8 and BP9 battery packs serves a dual purpose. First, it converts the 2.4V output of the two NiCd batteries to the 9V supply of the calculator. Second, it serves to regulate the AC input from the adapter to charge the battery. 

In a lot of cases the crystalline leakage from the damaged NiCd batteries followed the wires to the printed circuit board and destroyed not only the copper traces of the board but even some components on it. Unfortunately the Integrated Circuit (IC) in the 8-pin plastic housing labelled BP5IC is obsolete. This IC, a genuine DC/DC-converter developed by Texas Instruments for the pocket calculators was later introduced as TL496C to the open market and discontinued long time ago. 

In the meantime a smart engineer in Germany, Steffen Schmid, developed a 100% compatible replacement board for the BP7, BP8 and BP9 PCB's. It makes use of the latest DC/DC-converter technology and uses state-of-the-art surface mount technology. Find more information about the hints and tricks of this PCB and international sales information on Steffen's website


BP7 Battery Pack with original PCB installed.
Please note the 8-pin IC on the right. This is the obsolete component.


The replacement PCB developed by Steffen Schmid looks different but works perfect.


Fineprint: This information was compiled carefully but we are not responsible if someone destroys his calculator or himself.

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If you have additions to the above article please email:,

Joerg Woerner, February 12, 2003. No reprints without written permission.