1973 · East Bloc Pocket Calculator · Work 943 of 1,871
A workbench in the final assembly hall of a valve works in Mühlhausen in Thuringia in early spring, a woman's hands in pale blue work-coat sleeves setting a thick upright pocket calculator of black plastic into a low black charging stand, at its top a dark red display window with a soft red glow, below a worn pale grey key plate with cream-white keys, black keys and one red key, every key plain smooth and unmarked, a plain black plate at the foot, along the bench a row of identical black calculators standing in their stands, a shallow tin of small round button cells, grey daylight from high windows.
What it was used for
The minirex 73 was developed from April 1972 by a collective at VEB Funkwerk Erfurt and built at VEB Röhrenwerk Mühlhausen; the case came from the Atelier für Formgestaltung Karl-Marx-Stadt. It was shown at the Leipzig spring fair from 11 to 18 March 1973, after which series production began. It did the 4 basic operations. Power came from NiCd button cells of 1.2 volts and 225 mA from VEB Grubenlampenwerk Zwickau, because NiCd cells of R6 size were not available in the GDR; a purpose-built mains unit, into which the calculator was plugged, switched the cells off to extend their life and was also used for charging them. Alkaline R6 cells were rejected because they would have needed changing about every 10 operating hours. The keypad is larger than on the Busicom LE-120A, for calculating without looking.
What was new
The Heinz Nixdorf MuseumsForum lists the minirex 73 as the first pocket calculator developed in the GDR. The impulse came from outside: Otfried Steger, minister for electrical engineering and electronics, bought a Busicom LE-120A on a trip to Japan in early 1972 and asked Erfurt about it. A laboratory model ran on 20 June 1972, 3 months later 10 functional samples existed, and the collective received the Banner of Labour. The barb sits inside the machine: the calculating circuit was the imported TMS0105NC from Texas Instruments, obtainable under the embargo, in the Elektromuseum's account, only through creative trading. The GDR's copy of this chip, the U820D, was first used in the minirex 75.
What the sources leave open: None of the 3 sources gives a price in marks; in the HNF blog only a reader's comment gives 2,500 marks, for the minirex 75. The quantities of 2,000 for 1973, 10,000 for 1974 and 25,000 for 1975 are planned figures, not production figures. No source gives the digit count; the Elektromuseum implies the display type (LED) only indirectly. The HNF does not know how the TI chips reached Erfurt; museum-digital supports only the fair premiere and the successor minirex 74.