DATAMATH CALCULATOR MUSEUM

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 Unfortunately the Integrated Circuit (IC) in the 8-pin plastic housing labeled BP5IC is obsolete.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 PCBs. It makes use of the latest DC/DC-converter technology and uses state-of-the-art surface mount technology (SMT). Find more information about the hints and tricks of this PCB and international sales information on Steffen's website http://www.stschmid.de/calculators.

BEFORE

BP7 Battery Pack with the original PCB installed.
Please notice the 8-pin IC on the right. This is the obsolete BP51C component.

AFTER

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

+++ UPDATE May 2020 +++

Fellow calculator collector Lou Angelucci surprised us in April 2020 that he could locate the obsolete Texas Instruments TL496C (formerly known as BP51C-3A) and designed a replacement board for the BP7, BP8, and BP9 Battery Packs. He thoughtfully included a small switch to isolate the battery cells from the printed circuit board (PCB) while the unit is not in use to prevent any damage of the electronics from leaked NiCd cells.

BEFORE

BP7 Battery Pack with the original PCB installed.
Please notice the 8-pin IC on the right. This is the obsolete BP51C component.

AFTER

The replacement PCB developed by Lou Angelucci with the TL496C IC looks almost identical and works perfect.

We just converted a non-working BP7 Battery Pack with Lou's PCB and it looks, smells and works like new. Please get in touch with Lou if you are interested in one or more of his great replacement boards.

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

If you have additions to the above article please email: joerg@datamath.org.