Commodore Minuteman 2 (Version 2)

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.

The next iteration of Commodore's design language was introduced in 1974 with the Minuteman 3 series of calculators.

Dismantling the featured Minuteman 2 (MM.2 Version 2) manufactured in September 1972 by Commodore reveals two obvious changes compared to a MM.2 Version 1 manufactured three months earlier:

The printed circuit board (PCB) of the MM.2 Version 2 remained unchanged from its predecessor and sports a bold mark reading RAVEN 11870.

The 9-digit Hewlett Packard 5082-7450 display of the featured MM.2 Version 2 was manufactured by Hewlett Packard and uses a combination of one 4-digit HP 5082-7414 and one 5-digit HP 5082-7415 end-stackable module, each.

We recently discovered a Commodore Minuteman 2 (MM.2 Version 2) manufactured in May 1973 and decided to give it a full tear down - just to discover an array of 9 Monsanto MAN-3A 7-Segment LED modules again.

The PCB of the MM.2 Version 2 manufactured in May 1973 is identical to the PCB of the MM.2 Version 1 and sports a bold mark reading RAVEN 11870.

The electronics of the Commodore Minuteman 2 is centered around a Texas Instruments TMS0103 single-chip calculator circuit and - like most early designs of the wildly successful TMS0100 family - two SN75491 Segment Driver chips and two SN75492 Digit Driver chips, each. The remaining components on the PCB are mainly used to generate the necessary supply voltage of the TMS0103 and its clock signal for the internal timing.

The display module of the MM.2 looks familiar to us, it is still using an array of 9 Monsanto MAN-3A 7-Segment LED modules.



The keyboard assembly was manufactured on April 6^th, 1973 by Wild Rover Corp. in Norwood, New Jersey and seems to be pin-compatible with the original Texas Instruments Klixon design introduced already in 1971.

The Commodore Minuteman 2 is like its predecessor Minuteman 1 powered by 6 internal, rechargeable AA-sized batteries and uses an external MM-Type Charger / Power Supply.

Klixon™ is a trademark of Texas Instruments.

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

© Joerg Woerner, October 30, 2021. No reprints without written permission.