As we accumulate drawings and information for the Soemtron ETR 22x range of calculators we are making that information available here, but please note that this information is provided in good faith and will undoubtedly contain errors given the age and nature of the subject. Updates and corrections to the drawings are uploaded on an ad-hoc basis as we work on our current collection of Soemtron ETR 220, ETR 222 and ETR 224 machines and receive information from contributors. We do not accept responsibility for their subsequent use. The files will usually be in pdf format and a current copy of an Adobe Acrobat  reader will be needed. To download the files right click the relevant link and select "file save as ....". All files on this website are ©2007- www.soemtron.org and it's group websites  or the files respective owners.
Our circuit diagrams (schaltplan) are reverse engineered from our collection of Soemtron ETR calculators, some of which are in the process of being refurbished, hopefully to full working order. Our circuits are drawn on Pads Powerlogic 5.0 AutoCad LT, we claim copyright on these drawings only. We freely acknowledge that the original intellectual property rights of the Soemtron ETR series calculators resides with V.E.B.  Büromaschinenwerk  Sömmerda and their designers.
When referencing the drawings we have followed the original component idents as found on the boards. However to better fit in with the schematic drawing package, component references for the circuits are prefixed by the board number or ancillary function, EG. for Board 7 resistor R24 the reference is "7W24" (resistors are Widerstand in German), "KW2" is resistor R2 on the Keyboard. Missing or left over components are left on each circuit diagram until the potential problem with those components have been resolved.
If you have any further historical information, circuits, drawings, photographs, data or manuals about the Soemtron ETR 220, 221, 222, 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 here.
In reverse engineering our Soemtron's we have been very fortunate to have managed to obtain a copy of a few of the original German and Russian diagrams for the Soemtron 220, the following list is a translation of the German component references and terms that we have found so far, that were used on some of these drawings.