Western Auto Citation aka M4987 Version 4

The TMS0952 introduced with the original design of the M4986 was soon replaced with the TMS0972, a pin-compatible design dropping the additional resistors and capacitor and further reducing the manufacturing costs of the M4986 series. This contribution of cost cutting had a side effect for the customer, Texas Instruments decided to use with the TMS0972 an 8-digit LED display instead of the previous 9-digit display. While the 9^th (leftmost) digit was originally used only for the negative sign and didn't impact most calculations, should you try this example: 

Western Auto consequently changed the name of the M4986 from "electronic Wizard" to "Citation" to avoid any confusion with the operating instructions printed on the backside of the sales box.

Dismantling the featured M4987 with Date code 1577 LTA and manufactured in April 1977 in Lubbock, Texas reveals a very efficient and cost-optimized design with a single-sided printed circuit board (PCB) centered around a TMS0972 single-chip calculator circuit based on the TMS1000, the World's first Microcomputer.

The final step of cost reduction of the of the M4986 was introduced just a few months before its discontinuation and included a smaller encapsulation of the TMS0972 Chip. While the original design was using a 0.6” wide 28-pin DIP (Plastic Dual In-line Package with a 0.1” / 2.54 mm lead pitch) encapsulation, switched the final design to a 0.4” wide 28-pin SPDIP (Shrink Plastic Dual In-line Package with a 0.07” / 1.778 mm lead pitch) encapsulation.

Learn more about the evolution of the TI-1250 between June 1975 and its discontinuation in 1977.

Learn more about the different Product Labels used with the TI-1250 - here at the Datamath Calculator Museum we classify the featured M4986 as Hardware Version 4, PCB Type 3 and Product Label Style 3, Western Auto.

Don't miss the M4988 "Citation" based on the TI-1270 and marking the upper end of Western Auto's portfolio of portable electronic calculators in 1976/1977.

With the discontinuation of the TI-1200 family in 1977, Western Auto consequently replaced the M4987 "Citation" calculators and its siblings M4986 and M4988 with products based on the TI-1000 family. While the backside of the revised "Citation" calculators is missing any reference to the previous M4987 designation, sports the sales box a part number 66-4987-5, obviously a reference to the original naming schema. Please find in the table below a cross reference between Western Auto's 1976/1977 and 1977/1878 calculator offerings: