Texas Instruments TI-70 Digital Clock

This TI-70 electronic Digital Clock with its bright LED-display was introduced by Texas Instruments together with its sibling TI-71 already in 1974. While the TI-71 sports an alarm function, is the TI-70 a bare digital clock.

Both the TI-70 and TI-71 rely on the TMS3834 Digital Alarm Clock Chip and make use of an identical printed circuit board (PCB) with different options to distinguish between:

Dismantling a TI-70 (Serial Number A70-1012099) with Date code 504 and manufactured in December 1974 by Texas Instruments reveals a clever design centered around the TMS3834 Digital Alarm Clock Chip, an ITT 492 (SN75492) Digit Driver and a RCA CA3082 NPN Transistor Array as Segment Drivers mounted on a center mounted single-sided PCB.

The main PCB connects with flat wires on one side to a TIL370 Four-Digit Clock/Timer Numeric Seven-Segment LED Display and on the other side to a small PCB with the controls to adjust the time and set the brightness of the display. The individual transistors of the CA3082 chip control the current of the display segments based on the setting of the brightness switch accordingly. The main PCB sports additional connections for both the Alarm buzzer and Snooze button of the TI-71.

We recently discovered a TI-70 (Serial Number A70-1013272) with Date code 314 and manufactured in July 1974 and repaired at a later date sporting a TMS3834A on a different looking PCB but with similar components. The differences between the TMS3834 and TMS3834A are not yet discovered but might be related to the "p.m. bug" of the original design.

In one their earlier products Texas Instruments used a clock chip from on of their competitors, read more about the TI-3510 introduced already in December 1973.

Don't miss the last watch sold by Texas Instruments.

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

© Joerg Woerner, May 12, 2008. No reprints without written permission.