Texas Instruments SR-50

Date of introduction:  January 15, 1974 Display technology:  LED modules + lens
New price:  $169.95, DM 520.00 Display size:  10 + 2
Size:  5.8" x 3.2" x 1.3"
 147 x 81 x 32 mm3
Weight:  8.5 ounces, 240 grams Serial No:  211917
Batteries:  BP1 Date of manufacture:  wk 42 year 1974
AC-Adapter:  AC9200 Origin of manufacture:  USA
Precision:  13 Integrated circuits:  TMC0501, TMC0521
Memories:  1 Displays:  DIS288 (14*DIS279)
Program steps:   Courtesy of:  Joerg Woerner
Download leaflets: US: 2.2M Bytes)
DE: 1.9M Bytes) 
Download manual:   (US: 5.6M Bytes)

The wonderful electronic slide rule SR-50 marked a milestone in the history of calculators manufactured by Texas Instruments. It added trigonometric and hyperbolic functions, the logarithms and their inverses to the scientific functions of the SR-10, SR-11 and SR-16 line of calculators. The calculator was placed with big success against Hewlett-Packard's HP-35 and produced in high quantity. The internal construction was very rigid compared with other models. To reduce manufacturing costs and to give a similar appearance to the SR-52 and SR-56 calculators the SR-50 was replaced within 18 month with the SR-50A. Don't miss the rare SR-51.

SR-50_PCB2.jpg (139589 Byte)SR-50_PCB1.jpg (173439 Byte)On a first view the twins SR-50 and SR-50A look similar, but if you use them you'll feel the differences! If you search for the best SR-50, choose a model produced later than July 1974. Engineers at Texas Instruments changed the calculation algorithms and achieved a higher precision. Please find the comparison in the Calculator forensics.

With the TMC0500 Building Blocks Texas Instruments created a novel architecture for scalable scientific calculators. The architecture used minimum a 2 chip design with the TMC0501 Arithmetic Chip and the TMC0520 SCOM (Scanning and Read Only Memory) Chip but was expandable to a maximum of 8 SCOMs, additional RAM as program memory for programmable calculators, additional RAM for general purpose registers and even a chip driving a printer. Most scientific and programmable calculators from Texas Instruments between the years 1974 and 1982 like the SR-51, SR-60A and TI-59 use these chips. Please find all known calculators using the TMC0501 architecture here. Don't miss the odd TI-5230 desktop calculator. Don't miss the SR-50 manufactured for Dismac Industrial S.A. in Brazil changing the layout of the aluminum bezel.

Masaki Takada donated some wonderful pictures and this gives us the opportunity to view the inside of the SR-50.

Engineers use the clear case during the development of a product to check if the electronic and mechanical components fit neatly into the housing. sr-50_1.jpg (145797 Byte)
The side view gives you an impression of the upper and lower case shell and the printed circuit boards inside. sr-50_2.jpg (156942 Byte)
The bottom view gives you (from upper right to lower left) the opening of the rechargeable batteries, the huge calculator chips (TMC0501, TMC0521) and the power supply circuit. sr-50_3.jpg (137588 Byte)
The display frame covers the upper row of the keys and the two switches neatly. This gives you a very valuable design compared to e.g. the TI-30. sr-50_4.jpg (128978 Byte)
This wonderful pictures gives you an imagination of the curved lens above the red display. A perfect calculator! sr-50_5.jpg (131904 Byte)



The SR-50 is featured in the Texas Instruments Incorporated bulletins SR-50_FL and CB-SR50 dated 1974.

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If you have additions to the above article please email:

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