Soemtron ETR220 Downloads

Soemtron logo of unknown origin

This page has general information in downloadable form for the Soemtron ETR220 electronic calculator.  Updates and corrections to this information are uploaded on an ad-hoc basis as various corrections come to hand, but we do not accept responsibility for their subsequent use.  The files will usually be in pdf format so a current copy of an Adobe Acrobat reader will be needed[1].  To download the files right click the relevant link and select "file save as ....", or to view the files directly just click the link, assuming you have the pdf viewer installed!
All files on this website are ©2007– and its group websites[2] or the files respective owner.

Soemtron logo

If you have any further historical information, circuits, drawings, photographs, data or manuals about the Soemtron ETR220, 221, 222 and 224 or their manufacture, test equipment (Prüfgeräte) or you just know more about the Soemtron companies in general then please let us know, contact us.

English manuals
Engineering manuals recently received from Germany.
1 -Lageplan, a short extract of an unknown document (not item 3 below) with component placement drawings and track connections for the 12 main PCB assemblies.  (13.6Mb).
2 -Technische Instruktion, part two of a 1974 technical instruction manual, with board layouts, logic diagrams, circuits, assembly drawings and setup instructions.  (28.8Mb).
3 -Ersatzteilekatalog, a 1975 manual showing again the 12 main PCB assemblies but also including sub assembly drawings of the other major parts of an ETR220 including the keyboard, display, decimal point position switch, power supply and bypass regulator.  Part lists of the assemblies are given together with their Soemtron part numbers.  (18Mb)
4 -Part #'s, derived from the documents above, a list of all Soemtron part numbers current available to us.  (35Kb)
German manuals for the Soemtron ETR220
"Bedienung und übung" - "Operation and Exercises" by Manfred Sperfeld (1972) of V.E.B. Counting Machines, Potsdam.
English translation  - 2.2Mb pdf.  Translated from the German language publication above.
Scans (in German)  - 2.2Mb pdf.  Scanned copy of the German language publication.
"Bedienungsanleitung" - "Operating Instructions" by VEB Kombinet Zentronik (1976).
English translation  - 675Kb pdf.  English translation of the 1976 German publication.
Scans (in German)  - 3.2Mb pdf.  Scanned copy of the 1976 German publication.
Russian Technical Manual for the Soemtron ETR220
This 1972 manual is courtesy of Gerhard Just, it includes a detailed description of the logic elements, their component values, operation and even a timing diagram or two.  Gerhard and Ed Cabler have also kindly helped out with some of the Russian to English translation anomalies.
English translation  - - (version #26L,16.7Mb pdf, 19/03/2024).  This document has been reproduced from the 1972 Russian publication above.
Scans (in Russian)  - 10Mb pdf, scanned original Logic diagram  - 1.4Mb pdf
German Logic diagrams for the Soemtron ETR220
These drawings are courtesy of Bernard Green, they include component references and values, logic symbols and a diagram for each board and give an insight into what the logic designers were able to achieve in the functions of the Soemtron ETR220 with such basic, albeit almost primitive electronics then available in 1960's German Democratic Republic.
GatesAND - OR Gates
Buffers - 1Buffers
Buffers - 2More buffers
Delays & flip–flop inputsDelays & flip–flop inputs
Basic flip–flopsBasic flip–flops
Schmitt TriggerSchmitt Trigger
Clock oscillatorClock oscillator
Core driverCore driver
Core sense amplifierCore sense amplifier
Nixie tube driversNixie tube drivers
Power supplyPower supply
And the boards -
Board 12Cathode drivers and number key encoding 
Board 11Anode drivers, digit position decoder function keys encoding 
Board 10Display digit position counter 
Board 9Memory Register addressing 
Board 8Negative result latch plus three other undefined 
Board 7Function latches 
Board 6Control gating 
Board 5Function latches, Clock oscillator 
Board 4"E" register, misc. gating and drivers. 
Board 3"C" register 
Board 2Core Memory Read, Write and Inhibit drivers 
Board 1Core Memory and data sense amplifiers 

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