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Sinclair Cambridge models

The Sinclair Cambridge was introduced in summer 1973, and was the first of a range of a dozen models and variations.

This page illustrates the several varieties of the basic Sinclair Cambridge calculator, which can be distinguished by the key arrangements.
Here are what we believe to be all of the models in what we think is their chronological order.

Sinclair Cambridge type 1

Sinclair Cambridge type 1
Inside Sinclair Cambridge type 1
Inside a modified Sinclair Cambridge type 1

Sinclair Cambridge (type 1).

8 digits, red LED.

4-functions, constant.

Has [C] and [K] (constant) keys.

Batteries: 4x AAA.

Main integrated circuit - General Instruments Microelectronics GI-C550, here date coded mid-1973.

50 mm x 111 mm x 28 mm (2" x 4.4" x 1.1").

Made in England.

The first of the very small Sinclair Cambridge series, introduced in Summer 1973
Cost £43.95 GBP in Britain, and in the U.S.A. in January 1974 it cost US$79.95 as a build-it-yourself kit and US$99.95 fully assembled[1].

The case has a glossy finish, with a poorer quality moulding than usual for Sinclair. The main chip is in a more expensive ceramic package.

Catherine Palmer has kindly supplied the photograph above of the circuit board of a Sinclair Cambridge type 1 with a factory modification.  This has a second display driver integrated circuit from ITT (International Telephone & Telegraph) which has been laboriously soldered with flying leads to replace 8 diodes around the Bowmar display.  This may have been found necessary in order to produce a reliable display after the calculator went to market.

Catherine has photographs of more calculators and vintage technology at http://www.palmyria.co.uk/collections/miscantiques.htm 

Sinclair Cambridge type 2

Sinclair Cambridge type 2
Inside Sinclair Cambridge type 2

Sinclair Cambridge (type 2).

8 digits, red LED.

4-functions.
Has no K (constant) key, but has automatic constant on all functions i.e. the second operand of all calculations is automaically stored as the constant factor.
Has [C] and [CE] (clear last entry) keys.

Batteries: 4x AAA.

Main integrated circuit - Texas Instruments TMS0801NC, here date coded end of 1973.

50 mm x 111 mm x 28 mm (2" x 4.4" x 1.1").

Made in England.

Sinclair Cambridge type 3

Sinclair Cambridge type 3
Inside Sinclair Cambridge type 3

Sinclair Cambridge (type 3).

8 digits, red LED.

4-functions, constant.
Has [C/CE] (one press clears last entry and two presses clears everything) and [K] (constant) keys.

6v (4 x AAA).

Main integrated circuit - General Instruments Microelectronics GIMT-CZ550,here date coded to the end of 1975.

50 mm x 111 mm x 28 mm (2" x 4.4" x 1.1").

Made in England.

This Cambridge model is a later, more common, version of the Cambridge.
It was also available as a self-build kit, as pictured below.

Sinclair Cambridge type 3, version Manufactured in Spain

Sinclair Cambridge made in Spain

Javier Ortiz has kindly provided this photograph of the back of a Sinclair Cambridge type 3 manufactured under licence in Spain.

It says "FABRICADO EN ESPANA
Bajo licencia sinclair"

Translated "Made in Spain
Under licence sinclair"

Sinclair Cambridge type 3, self-build kit

Sinclair CambridgeKit

A Sinclair Cambridge calculator kit, still shrink-wrapped in the polystyrene container.

Sinclair Cambridge Kit
Sinclair Cambridge Kit

The assembly instructions for the Sinclair Cambridge calculator kit.

The components of the Sinclair Cambridge calculator kit, there is also a bag of small parts out of view.

Sinclair Cambridge type 4

Sinclair Cambridge type 4
Inside Sinclair Cambridge type 4

Sinclair Cambridge (type 4).

8 digits, red LED.

4-functions, %.
Has [C], [CE] (clear last entry), and [%] keys.

Batteries: This model takes only 2x AAA.

Main integrated circuit - General Instruments G-595, here date coded to the end of 1975.

50 mm x 111 mm x 28 mm (2" x 4.4" x 1.1").

Made in England.

Note the use of LED displays made by Bowmar, the pioneering U.S. calculator manufacturer.

Price plummets:
When first introduced in summer 1973 the Cambridge cost £43.95 Sterling [about US$100].
In Summer 1977 the mail-order discount price had dropped to £8.95 Sterling [about $US15], one fifth of the original price.

 

 

Reference

  1. "Skinny mini", Popular Science, January 1974, p69

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© Text & photographs copyright Nigel Tout   2000-2019  except where noted otherwise.