I have a HP-97 that I purchased from a Cal-Tech student while attending Pasadena City College in 1979. I haven't used it in a while but I recently moved and came across it. I found that the batteries were NG, so I replaced the battery pack with SANYO Quick Charge NiCad batteries, N-1200SCF. They are 1.2v, 1100mah units. After reassembling the pack, and charging the pack overnight, I turned on the calculator and right away within a few seconds had a low-battery LED indication. I then removed the pack and measured the voltage...below 3 volts. When I assembled the pack, each battery showed a voltage of approx. 0.7 volts per cell. Obviously, the pack did not charge overnight. Today, I have placed the pack on an external charger, charging at 280ma (max is 350ma for quick charge). A previous check about an hour ago showed the pack at 5.63 volts. I'm sure that I have a problem with the charging circuit of the calculator. Does someone have a schematic of this circuit that I can use in troubleshooting this problem?? Any info would be greatly appreciated. TIA..sok.
HP-97 Power/Charging Problem
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