DATAMATH  CALCULATOR  MUSEUM

Exactra 23 by Texas Instruments 

Date of introduction:  October 1974 Display technology:  LED-stick w/o lens
New price:   Display size:  8 + sign
Size:  5.1" x 2.9" x 1.3"
 130 x 74 x 34 mm3		    
Weight:  5.1 ounces, 144 grams Serial No:  2300021274
Batteries:  3*AA  Date of manufacture:  wk 48 yr 1974
AC-Adapter:  AC9160 Origin of manufacture:  USA
Precision:  8 Integrated circuits:  TMS0803, SN27882
Logic:  Chain Displays:  
Memories:      
Program steps:   Courtesy of:  Joerg Woerner
    Download manual:   (US: 1.9M Bytes)

The Exactra 23 could be called the fully loaded model in the cheap Exactra line. It sports an 8-digit display, a %-key and a connector for an external power supply. This position in the Exactra line is demonstrated to the customer with a valuable golden line around the keyboard.

Dismantling the Exactra 23 revealed two small surprises. First of all the LED-display found in this particular calculator was manufactured by Bowmar. We know the Opto-stick display with he small numbers already from the TI-2500B.

Second surprise is the TMS0803 single-chip calculator circuit known from the Exactra 21 and Exactra 22. But these siblings miss the %-key - once again the "power of marketing". Nevertheless the Exactra 23 uses a different layout of the printed circuit board (PCB)r. We identified a SN27882 7-channel digit driver manufactured by Texas Instruments for the LED display. Two NPN bipolar junction transistors (BJTs) with additional resistors are used for the remaining digit drivers. The other parts on the PCB form a small power-converter to generate the VDD and VGG supplies of the TMS0803 chip with three AA-sized batteries. 

A similar calculator was sold as Citation M4993 by the distribution company Western Auto and by Montgomery Ward with the TXI-8661A.



 

horizontal rule

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

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