Craig Model 4501

Date of introduction:  September 1971 Display technology:  LED-stick
New price:  $239.95 Display size:  8
Size:  5.2" x 3.1" x 1.5"
 133 x 78 x 37 mm3
Weight:  10.9 ounces, 310 grams Serial No:  106617
Batteries:  6*AA NiCd Date of manufacture:  wk 12 year 1972
AC-Adapter:   Origin of manufacture:  USA
Precision:  8 Integrated circuits:  TMS0103, 2*SN75491, 2*SN75492
Memories:   Displays:  9*Monsanto MAN-3A or
 Bowmar Optostic
Program steps:   Courtesy of:  Joerg Woerner

The Bowmar 901B, here with the OEM-label of Craig Cooperation Machines was the first "True-Pocket-Size" calculator mainly based on components of the Texas Instruments company. One of the advantages of the sleek housing of the Bowmar 901B and its two identical twins Commodore C110 and this Craig Model 4501 was the slightly angles display to improve reading the small numerals of the LED display.

Dismantling this Craig Model 4501 manufactured in March 1972 by Bowmar/Ali Inc. of Acton, Massachusetts, USA reveals immediately on the backside of the calculator a bold mark reading PM901-400/E - translating into Bowmar part number PM901B-400 with Revision E. We spotted this PCB-Mark not only with the Bowmar 901C but the Commodore Minuteman 1, too. In addition you'll notice a rechargeable battery pack mounted into the bottom shell of the housing, it consists of six AA-sized NiCd cells.

Removing the main electronics of the featured calculator from its housing shows the original Texas Instruments Klixon™ keypad hiding most of the calculator electronics and we identify only two display driver chips and the LED display. The electronics of the Craig Model 4501 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 featured Craig Model 4501 looks familiar to us, it is still using an array of 9 Monsanto MAN-3A 7-Segment LED modules.

Later in production Bowmar used their own Opto-stic LED displays like the one located in a Craig Model 4501 with serial number 226055 and manufactured around June 1972.

Don't miss the later Craig 4510 manufactured by a Japanese company, but nevertheless "very Texas Instruments".

Klixon™ is a trademark of Texas Instruments.

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© Joerg Woerner, December 5, 2001. No reprints without written permission.