Texas Instruments TI-2550 (1st design)

Date of introduction:  January 10, 1974 Display technology:  LED-stick
New price:  $99.95, DM 298.00 Display size:  8
Size:  6.5" x 3.2" x 1.8"
 165 x 80 x 45 mm3
Weight:  7.8 ounces, 220 grams Serial No:  2550149705
Batteries:  3*AA NiCd or 4*AA Alkaline Date of manufacture:  wk 29 year 1974
AC-Adapter:  AC9130 or AC9120 Origin of manufacture:  USA
Precision:   Integrated circuits:  TMS0601
Memories:  1    
Program steps:   Courtesy of:  Joerg Woerner
    Download manual:   (US: 1.8M Bytes)

Roughly one year [or later - continue here] after the introduction of the famous TI-2500 alias Datamath the engineers at Texas Instruments added a full memory onto the calculator chip. Integrated into a housing similar to the wedge shape of the SR-11 it was named TI-2550.

TI-2550_PCBA.jpg (126437 Byte)Today we know two different versions of the TI-2550:

The first calculators used a display module without magnification lenses (actually a Bowmar Opto-stick), later TI-2550 calculators got the bubble lenses known from the TI-1200 and TI-30.

A close relative of the TI-2550 was sold through the American department store Montgomery Ward. Compare the TI-2550 with the P200.

The same housing and a very similar keyboard was used by the TI-150.

Datamath™ is a trademark of Texas Instruments.


Introduction of the TI-2550

TI-2550_PCBP.jpg (71492 Byte)Recently we received from a fellow engineer of a Dallas based company a parcel with some calculator prototypes.

One of the surprises was a very early TI-2550 with a Date code on the calculator chip indicating end of June 1974 as manufacturing date. This prototype makes use of 9 single LED-modules known from the TI-2500 Version 3. Two explanations:

The TI-2550 was introduced later in 1974 as we assumed.
This particular calculator was repaired and the first series 
used the single LED-modules instead the Bowmar Opto-stick.

The TI-2550 is featured in the Texas Instruments Deutschland GmbH leaflet ER-1975 dated 1975.

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© Joerg Woerner, October 23, 2003. No reprints without written permission.