DATAMATH CALCULATOR MUSEUM
Commodore Minuteman 2SR
|Date of introduction:||February 1974||Display technology:||LED-stick|
|New price:||$69.00||Display size:||8|
|Size:|| 6.0" x 3.5" x
153 x 90 x 36 mm3
|Weight:||7.4 ounces, 210 grams||Serial No:||79097|
|Batteries:||4*N NiCd||Date of manufacture:||mth 03 year 1974|
|AC-Adapter:|| Type MM 3
6.0V 200mA DC
|Origin of manufacture:||USA|
|Precision:||8||Integrated circuits:||MOS MCS2523, SN75491, ITT 492-5|
|Memories:||Displays:||National Semiconductor NSN 98B|
|Program steps:||Courtesy of:||Joerg Woerner|
Commodore Business Machines (CBM) introduced with the C110 already in September 1971 their first portable electronic calculator, actually a rebranded Bowmar 901B, better known as Bowmar Brain.
While the C110 was a rather short-lived product, did it pave the way to an incredible success story. Its successor Minuteman 1 was introduced within just a few months and started a completely different design language but still using Bowmar electronics. The next evolution - consequently named Minuteman 2 - replaced first the Bowmar electronics and then the Texas Instruments Klixon keyboard with Commodore's own designs. It took another iteration with the Minuteman 2SR to drop even the Texas Instruments calculator chips and replace it with a design from MOS Technology, a company Commodore acquired in October 1976 and fueling in October 1977 a revolution with the PET2001 (Personal Electronic Transactor), the best selling "Personal Computer" of its time.
|C110||September 1971||Bowmar||Bowmar||TI TMS0103||TI Klixon||Monsanto MAN-3A|
|Minuteman 1||January 1972||Commodore||Bowmar||TI TMS0103||TI Klixon||Monsanto MAN-3A|
|TI TMS0103||TI Klixon||Monsanto MAN-3A|
Wild Rover Corp.
|Minuteman 2SR||February 1974||Commodore||Commodore
|MOS MCS2523||HEC MM-4
The next iteration of Commodore's design language was introduced in 1974 with the Minuteman 3 series of calculators.
Dismantling the featured Minuteman 2SR (MM.2SR) manufactured in March 1974 by Commodore reveals some major changes compared to its predecessor MM.2:
| The rather large Wild Rover Corp. keyboard
was replaced with a much smaller keyboard coming right out of a Minuteman 3 calculator
The six AA-sized rechargeable batteries were replaced with four smaller N-sized cells
The TMS0103 single-chip calculator circuit was replaced with a MOS MCS2523 chip
The printed circuit board is much smaller than before and sports significantly fewer components
The Monsanto MAN-3A 7-Segment LED modules or Hewlett Packard 5082-7450 LED display was replaced with a National Semiconductor module
printed circuit board (PCB) of the Commodore Minuteman 2SR is centered around a
MCS2523 single-chip calculator circuit manufactured by MOS Technology and
supported by one
SN75491 Segment Driver chip and one ITT
492-5 (SN75492) Digit Driver chip. The
remaining components on the PCB are mainly used to generate the necessary supply
voltage of the MCS2523 and its clock signal for the internal timing.
The display module of the MM.2SR looks was manufactured by National Semiconductor and used 3 small light bars per segment.
The electronics of the MM.2SR is powered by four N-sized rechargeable NiCd batteries and uses an external Type MM3 charger.
Klixon is a trademark of Texas Instruments.
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© Joerg Woerner, October 30, 2021. No reprints without written permission.