Texas Instruments TI-150

Texas Instruments introduced with this TI-150 in December 1974 a rather unusual calculator combining the wedge-shaped housing of the TI-2550 with the basic functionality of the Datamath II a.k.a. TI-2550-II and a Panaplex Style gas-discharge display. A small detail reveals the position of the TI-150 in Texas Instruments' "Basic Calculator Portfolio": The silver trim around the display frame, known from the first generation of the SR-10, placed it obviously in the upper-right corner of price over performance.

The date code 465 stamped on the backside of the featured TI-150 would indicate a manufacturing date in week 46 of November in the year 1975, to our understanding rather unlikely. We assume that this calculator was serviced in November 1975.

Dismantling this TI-150 manufactured probably in December 1974 or January 1975 reveals a design centered around a TMS0852 single-chip calculator circuit compared to e.g. the TMS0803 located in the TI-2500-II. Please notice the date code 7443 (third week of October 1974) printed on the TMS0852.

The TMS0852 found its way with slightly modifications into the Canon Palmtronic LD-series. Don't miss the LD-80.

The TMS0852 chip is complemented on the main printed circuit board (PCB) by discrete transistors to drive the high-voltage gas-discharge display.

The keyboard PCB of the TI-150 is identical to the TI-2550 but lacks the upper row of keys for the Memory functions.

How rare is the TI-150?

This is for calculator collectors the most important question - and the TI-150 seems to be pretty rare. Texas Instruments spent a fortune to develop this oddball in its calculator line (unique TMS0852 single-chip calculator circuit, miniaturized Panaplex Style gas-discharge display, unique AC9150 AC-Adapter) but left the design of the sales packaging unfinished.

Roger Whitaker, Lead Engineer of the TI-150 confirmed an estimated number of about 4,000 produced units:

The TI-150 was the only handheld to use a plasma display. It has a character height of 0.2 inch and was intended as an "Executive" calculator. The case was the TI-2550's. The comments on Joerg's page are basically correct. It lacked the memory feature and was over priced. The production figure of 4,000 is probably right, although I wonder if they actually sold that many. It definitely was the wrong calculator at the wrong time. The plasma display requires about 150 volts to fire the segments. The TMS0855 is probably similar to the TMS0852 in having relatively high voltage display drive output architecture, but driving the plasma display required use of separate discrete high voltage PNP transistors, 2N5400 or 2N5401's as I recall without opening up my TI-150 to look. My 150 is Serial Number 010038 which was a prototype. Something else that most people may not know is that TI made its own plasma displays at a plant in Sherman. They were a direct replacement for the Burroughs Panaplex. I think that my TI-150 may have one of them. They also made the larger ones for the desktop units, too.

Fellow collectors - if you own a Texas Instruments TI-150 calculator,  please report us the serial number and date code from the back of the calculator (optionally from the TMS0852 calculator chip) for our Database.

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

© Joerg Woerner, December 5, 2001 and March 14, 2020. No reprints without written permission.