Montgomery Ward P800 aka TXI-8642A

This boxy calculator does not look like a Texas Instruments product. To identify it, you have to know more about the coding on the product labels used by Montgomery Ward:

Models starting with

• TXI were manufactured by Texas Instruments
• DAN were imported by APF Electronics, Inc.
• DNS were manufactured by National Semiconductor (later Novus)
• EKJ were imported by Kings Point Corporation
• GLE were manufactured by Lloyd's Electronics, Inc.

If you dig deeper into the calculator you'll notice that the P800 is very similar to the TI-2500 Datamath. The circuit diagrams look identical, the single-chip calculator circuit is either the TMS0109 borrowed from the TI-3000 or the TMS0103 found in the Bowmar 901B. The other components located on the printed circuit board (PCB) of the featured calculator manufactured in 1973 are well known from the reference design of the TMS0100, namely two SN75491 Segment Driver chips and two SN75492 Digit Driver chips, each for the LED display composed of two pre-configured LED-modules (DIS40, DIS95) are based on the TIL360 arrays and soldered directly to the PCB. 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 keyboard is clearly identified as a standard Klixon™ product manufactured by Texas Instruments. The color of the housing, the LED-modules and some other details like the rubber feet are known from the Datamath calculator.

A similar calculator was sold by Longines Symphonette with the Electronic Calculalator and by Radio Shack with the EC-200.

Don't miss the rare TXI-8661A based on the Exactra 23 calculator.

Datamath™ and Klixon™ are trademarks of Texas Instruments.

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

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