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Texas Instruments TI-55 III

Date of introduction:  1986 Display technology:  LCD
New price:   Display size:  8 + 2
Size:  5.8" x 2.8" x 0.85"
 147 x 72 x 22 mm3
   
Weight:  3.0 ounces, 84 grams Serial No:  
Batteries:  2*LR44 Date of manufacture:  wk 04 year 1986
AC-Adapter:   Origin of manufacture:  USA
Precision:  11 Integrated circuits:  CD4555, CD4556
Memories:  1-8    
Program steps:  56-0 Courtesy of:  Joerg Woerner

If you compare this calculator with its predecessor TI-55-II you'll immediately ask: Why that step backwards in design? The TI-55-II looks valuable with the metal housing, the molded keys, the perfect print on the keyboard plate and the golden ration of width to height. But usually calculators had to work and not to shine on the desk.

To be honest to you, the keyboard of the first slanted series was terrible. After some years of usage the keys decided to bounce or to malfunction. Texas Instruments decided to replace the keyboard technology borrowed from the Majestic line (TI-55) with a somewhat Japanese technology. If you ever opened a TI-30 or TI-1250 you noticed that white plastic sheet with the wires and the metal domes. With the key you press down the dome, this one snaps towards the wires and shortenes them. The new technology uses a rubber plate with small conductive elements inside. If you press a key, you move these conductive elements against small traces on the printed circuit board and shortenes them. This gives a smooth feeling compared to the "snap" of the elder calculators.

Most calculators of the first generation were replaced:

First generation Second generation
TI-55-II TI-55 III
TI-57 LCD TI-57 II
BA-55 BA-54
LCD Programmer LCD Programmer II

The very first calculators of the TI-55 III series kept the old and confusing name "TI-55 II". View a very rare TI-55 II manufactured in Taiwan here

TI-55-III_Switch.jpg (21749 Byte)Within some weeks the mistake was corrected and a lot of TI-55 III calculators left the production lines in Taiwan. Between 1985 and 1986 Texas Instruments created an amazing number of different designs in the "Second Generation - Slanted LCD" calculator series just by moving production to far-east contract manufacturers, fetching manufacturing back to their own facilities and revising the design. Please click on the picture at the right as a switchboard to all known versions of the Second Generation Slanted LCD calculators.

The technical details behind the housing are similar, the first and second generation of each calculator pair use the same display and the same integrated circuits.

TI-55_PCB.jpg (129123 Byte)The picture on the right gives you an inside view of the three different TI-55-II and TI-55-III discovered up to now. From left to right you find:

TI-55-II manufactured in 1981 in US. 
   Known for the bouncing keyboard introduced with the slimline calculators.
TI-55-II resp. TI-55-III manufactured by Inventec Corporation in Taiwan between
   1984 and 1985. The PCB used in Compal's calculators could be found here.
TI-55-III manufactured in 1986 either in US or Italy. 
   Uses far-east keyboard technology with conductive rubber together 
   with contact fingers on a flexible PCB.

A little exotic within the slanted line is the black coloured TI-60 and the rare BA-III, they use another display. The TI-53 misses five keys.

Within Europe this calculator was sold under the model designation TI-56. Even sibblings like the Jeppesen Sanderson prostar Flight computer were changed from the old design to the new design.

 

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

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