Soemtron Downloads

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 so you will need a current copy of an Adobe Acrobat reader which you can get from here. To download the files right click the relevant link and select "file save as ....", to view the file directly just click the link, assuming you have a pdf viewer installed !. Most of the files on this website are ©2007- www.soemtron.org - www.soemtron.com, all other files and pictures on this site are copyrighted to their 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. The circuits are drawn on Pads Powerlogic 5.0 and 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 fit in with the schematic drawing package used for this project, 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 information, circuits, drawings, photographs, data or manuals about the Soemtron ETR 220, 221, 222, 224 or their manufacture please contact us here, meanwhile please use the datasheet links below, or menu navigation (left) to get to the downloads page for the relevant Soemtron ETR machine.

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.

And lastly as we cannot think of anywhere else to put this bit of information about the Soemtron Prüfgerät at the moment !.
Prüfgerät and Service Connectors.
We have tabulated the differences between the service connectors in the Soemtron 22x machines, as at some stage in the future we intend to re-create a "Prüfgeräte" or test unit for our Soemtrons. To generate the service connector difference list we compared the service connectors of our ETR 220 machines with the ETR 220 service connector listing and Prüfgerät front panel diagram from the Russian Technical manual, and then added the connections from our ETR 222 and 224 machines.

The Prüfgerät would appear to have two (common ?) 32 pin leads that connect to the main card cage of each machine type, with a display and test point matrix of five rows of ten signals on it's front panel, along with a few other test points and switches. Comparing the service connector pinning to the Prüfgerät front panel drawing on page 185 of the Russian Technical manual gives a very close match suggesting that the two cables are one-to-one pinned and that there may also have been front panel overlays for the display matrix to change the signal names between the various models. If you have any circuits, drawings, photographs, data or other information about the Soemtron Prüfgerät please contact us here

• Compare - (Each link opens in a new window)
• Service connector variants
• Prüfgerät front panel layout

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