Technico LC-74CK (Version 2)

Does this Technico LC-74CK calculator look familiar to you? Inventa Electronics Corporation of Taipei, Taiwan started already in 1975 manufacturing and marketing calculators under the Technico brand. Inventa Electronics Co. is today known as Inventec Corporation, one of the World's largest manufacturers of mobile devices and computers. We discovered the LC-74CK, and most important the SL-674CK, on our quest to learn more about the roots of the TI-1755 SLR introduced in 1983. While we found proof that TI-1754, TI-1755, TI-1756 and TI-1757 II are actually rebranded Inventa calculators, doesn't fit the TI-1755 SLR into the line. We decided for a thorough tear-down of the SL-674CK and the TI-1755 SLR to learn more about their relationship.

Dismantling the featured Technico LC 74CK manufactured in March 1985 by Inventa Electronics Corporation in Taiwan reveals a clean design centered around a Sharp LI3033M single-chip calculator circuit soldered on a double-sided printed circuit board (PCB) and powered by two small LR54 (LR1130) batteries. Learn how to decipher the 552C date code on the pictured Sharp chip.

Inspecting the PCB of the Technico LC-74CK calculator brought our attention to a small mark reading IO074D-05C. We found a similar PCB-Mark reading I074F-02B with the LC-741CK and started compiling a list of the PCB-Marks on calculators manufactured by OEMs for Texas Instruments.

Don't miss the almost identical LC-741CK, a "Checkbook" Calculator with a unique [MRC] key - meaning if you accidentally press the button twice your Balance is gone.

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

© Joerg Woerner, April 16, 2020. No reprints without written permission.