Texas Instruments TI-2550 II

Date of introduction:  October 17, 1975 Display technology:  Fluorescent
New price:  $49.95 Display size:  8
Size:  5.8" x 3.2" x 1.3"
 147 x 81 x 32 mm3
Weight:  6.7 ounces, 190 grams Serial No:  085935
Batteries:  BP2 Date of manufacture:  wk 09 year 1976
AC-Adapter:  AC9130, AC9130A Origin of manufacture:  USA
Precision:   Integrated circuits:  TMS1071 (AP 7545)
Memories:   Displays:  Itron FG95A1
Program steps:   Courtesy of:  Joerg Woerner
    Download manual:   (US: 2.8M Bytes)

Its product name gives you a first idea of this calculator: It is the successor of the TI-2550, an early, wedge shaped basic calculator.

The housing used for the TI-2550 II is identically to the SR-16 II, the difference is the keyplate and the underlying keyboard frame. The TI-2550 II uses two sliding switches and a green Vacuum Fluorescent Display (VFD), a rare combination in TI's calculator history.

The featured TI-2550 II with Date code 0976 LTA was manufactured in February 1976 by Texas Instruments in their Lubbock, TX facility. Dismantling this TI-2550 II reveals a design centered centered around a TMS1071 single-chip calculator circuit connected to a 9-digit Itron FG95A1 display and powered by a BP2 battery pack with two AA-sized rechargeable NiCd batteries.

This calculator was the first use of the TMS1070, a modification of the original TMS1000 LSI MOS chip to directly interface with low-voltage VFDs up to 35 Volts. The TMS1001 found in the SR-16 used two external digit drivers for its Light Emitted Diode display.

This beautiful calculator was quickly replaced by the TI-2550 III, a keyboard without a [+/-] key was not too useful. Ever wondered what's beneath the empty position of the metalized keyplate? Yes, a fully functional [+/-] key as featured with the Privileg 861 MD! And the TI-2550 II is hiding even more functionality of the TMS1071 chip, learn more about Characterization of Single-Chip Calculator Circuits with the DCM-50A Platform.

A similar calculator chip was used with the innovative Canon MD-8 sporting a multi-line display. 

Don't miss the TI-2550 II for the vision impaired people, the Schoenherr Braillotron 2550 II.

The TI-2550 II is featured in the Texas Instruments Deutschland GmbH leaflet ER-1976 dated 1976.

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If you have additions to the above article please email:

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