The Museum of HP Calculators

HP Forum Archive 10

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Re: HP-41 internal upgrade. ????
Message #1 Posted by David Smith on 15 Jan 2003, 6:19 p.m.

Yes, it is a speedup circuit. Some used some keyord commands to turn it on and off (you should see some wires going to the keyboard). Others used a magnetic reed switch and an external magnet to control them. Finally some used a tiny pushbutton mounted in the charger port.

The connection to the CPU card is not a diode, but the timing capacitor. The chips on the speedup board are usually a CMOS flip/flop and an analog switch.

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