Soemtron Downloads

As we accumulate drawings and other information for the Soemtron ETR22x 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 ETR220, ETR222 and ETR224 machines and receive information from contributors.  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[1] reader will be needed to view them.  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 its group websites[2] or the files respective owner.

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[3] or AutoCad LT[4] 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.[5] Büromaschinenwerk[6] Sömmerda and their designers.

When referencing the drawings we have followed the original component idents as found on the boards, however to better fit with the schematic drawing package we are using, component references for the circuits are prefixed by the board number or ancillary function. E.g. 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 any potential problems with those components have been resolved.

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.

In reverse engineering our Soemtrons 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 ETR220, 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.

Datasheets for some of the components used in the Soemtron 22x series calculators -
Z570M - Nixie tube, digits 0-9, 13mm 2mA no decimal point (pin 4?), RFT, P#00-560-9558-3.
Z573M - Alternate nixie tube[7], digits 0-9, 13mm 2mA with decimal point (pin 10?), RFT.
GS121 - Germanium PNP transistor, 30V 100mA 150mW max, RFT.
2SB75 - Germanium PNP Transistor, 30V 100mA 150mW max, Hitachi.
2SB77 - Germanium PNP Transistor, 45V 100mA 150mW max, Hitachi.
1N35   - Germanium diode, 50V 100mA 80mW max, BKC Intl.
GAZ17 - Germanium diode, 25V 20mA 100mW max, HFO.
KY130 - Silicon diode, 100V 300mA max, Telsa.

Part number list - a list of all Soemtron part numbers currently available to us from various documents (35Kb)

3D CAD -
Multiple 3D CAD models of various Soemtron parts have been created using the latest version of IronCAD 3D and they can be edited with a free 30 day trial[8], or viewed with a copy of IronCAD Compose[9].  The files are supplied in IronCAD native (.ics) and Step (AP214) formats within a zipped file.

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