Heathkit IC-2100

This Heathkit IC-2100 was the last desktop calculator sold as a kit to hobbyists in a line started in March 1972 with the IC-2008, immediately followed by the IC-2008A and the IC-2108 introduced in December 1973. The IC-2100 shares its design with the IC-2108.

Dismantling the featured Heathkit IC-2100 sold in March 1975 to an American hobbyist and assembled in picture-perfect quality, reveals a design centered around a Rockwell A4001PC single-chip calculator circuit in its signature 42-pin quad in-line package (QIP) on a conveniently large printed circuit board (PCB) surrounded by the power supply and many discrete transistors and other components.

The Rockwell A4001PC single-chip calculator circuit was introduced in 1974 and added to the usual four basic functions both a full memory and multiple scientific functions. The A4001PC chip is know for its not so great implementation of the integrated computing algorithm and running Mike Sebastian's "Calculator forensics" returns an unacceptable bad result of 10.4382 instead the expected value close to 9.0000. We know this chip already from both the Canon F-5 and Faber-Castell TR3 calculators introduced in 1974, too.

The Main-PCB is connected in typical Heathkit tradition with individual wires to the Keyboard-PCB and a third PCB with discrete high-voltage drivers and three 3-digit Sperry SP-353 planar neon gas discharge "Panaplex II" display modules.

The Keyboard-PCB is using twenty-six individual short-stroke push-button switches for the numbers and functions and two rocker switches for power and Radians/Degrees Mode selection.

The IC-2100 calculator was available till October 1974 when Heath stopped selling their own calculators and offered fully assembled calculators from National Semiconductor instead.

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

© Joerg Woerner, March 19, 2023. No reprints without written permission.