Downloads
Soemtron Downloads
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As we accumulate drawings and information for the Soemtron 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. Updates and corrections to the drawings as we work on our current Soemtron ETR 220 project are uploaded on an ad‑hoc basis as they are finished. We do not accept responsibility for their 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 !. All files on this page are ©2007-9 soemtron.org, all other files and pictures on this site are copyrighted to their respective owners.
All circuit diagrams are reverse engineered from a Soemtron ETR 220 that we own and are in the process of re-conditioning, 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 intellectual property rights of the Soemtron ETR series calculators resides with V.E.B. Büromaschinenwerk Sömmerda and their designers. The following list is a translation of the German component references and terms used that we have found so far.
| Component / Term | Reference | Translation |
| Resistor | W | Widerstand |
| Diode | GR | GleichRichter |
| Flip Flop | Bistabile Kippstufe | |
| Carry | Ubertrag (UBER) | |
| Write | Schrieb | |
| Quality standard | 1 - 3 | Güteklasse |
| Many thanks to Philipp Maier for the above translations. | ||
| Ferrite core driver | Ferritekerntreiber | |
| Measure or Testpoint | MP | MessPunt |
| Read | Lesen / LES | |
| Read amplifier | Wiedergabe verstarker | |
| Write | Schreib | |
| Many thanks to Bernard Green for the above translations. | ||
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 (PADS Powerlogic), 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 information, circuits, drawings, data or manuals about the Soemtron ETR 220, 222, 224 or their manufacture please contact us here
| Circuit and Logic diagrams - | ||||
| (See the "Snagging list" file for the current list of things to check on the circuits drawn so far) | ||||
| 1 | Keyboard | Keyboard circuit | updated | 10/6/2010 |
| 2 | Display | Display circuit | updated | 10/6/2010 |
| 3 | Backplane | Backplane circuit | updated | 11/12/2009 |
| 4 | Board 12 Board 12 |
Cathode drivers and numeric key encoding circuit Display drivers and numeric key encoding logic diagram |
updated updated |
11/12/2009 6/11/2009 |
| 5 | Board 11 Board 11 |
Anode drivers and function key encoding circuit Logic diagram |
updated updated |
11/12/2009 6/11/2009 |
| 6 | Board 10 Board 10 |
5 bit display "Z" counter circuit Logic diagram |
updated updated |
10/6/2010 10/6/2010 |
| 7 | Board 9 Board 9 |
F2,5-6 function latched circuits, including register addressing Logic diagram |
updated updated |
10/6/2010 10/6/2010 |
| 8 | Board 8 Board 8 |
F1/3, VER and MZ function latched circuits Logic diagram |
updated updated |
10/6/2010 10/6/2010 |
| 9 | Board 7 Board 7 |
B1-4, VOR and R function latches circuit Logic diagram |
updated updated |
11/12/2009 6/11/2009 |
| 10 | Board 6 Board 6 |
Control gating circuits Logic diagram |
updated updated |
11/12/2009 6/11/2009 |
| 11 | Board 5 Board 5 |
V, SCHRIEB, S1 function latches and 25Khz clock circuits Logic diagram |
updated updated |
11/12/2009 26/11/2009 |
| 12 | Board 4 Board 4 |
Arithmetic unit E Register (input), Carry latch and digit drives 0/1 circuits Logic diagram |
updated updated |
11/12/2009 27/11/2009 |
| 13 | Board 3 Board 3 |
Arithmetic unit A Register (output) and digit drives 5-9 circuits Logic diagram |
updated updated |
11/12/2009 6/11/2009 |
| 14 | Board 2 Board 2 |
Core memory drivers and decoding circuits Logic diagram |
updated updated |
11/12/2009 6/11/2009 |
| 15 | Board 1 Board 1 |
Core store, read amplifiers and digit drives 2-4 circuits Logic diagram |
updated updated |
11/12/2009 6/11/2009 |
| 16 | Supply | Power supply circuit | updated | 11/12/2009 |
| 17 | Block | Overall block diagram | updated | 26/11/2009 |
| Complete circuit | All current circuits for the Soemtron 220 (5.3Mb file) | updated | 10/6/2010 | |
| Complete logic | All current logic diagrams for the Soemtron 220 (1.6Mb file) | updated | 10/6/2010 | |
| 220 net list | Net list for the Soemtron 220 circuits (309Kb text file) | updated | 23/9/2008 | |
| Snagging list | Current problems with the circuits for the Soemtron 220 | updated | 23/11/2009 | |
| Datasheets for some of the components used in the Soemtron 220 | |||
| 2SB75 | Transistor datasheet | 2SB77 | Transistor datasheet |
| Z560M | Nixie tube datasheet | KY130 | Silicon Diode |
| 1N35 (GAZ17) | Germanium Diode | ||
| Russian Technical Manual for the Soemtron 220 | |
| These manuals are courtesy of Gerhard Just, and they include a basic description of the logic elements, their component values, operation and even a timing diagram or two. Gerhard has also kindly helped out with some of the translation anomalies. | |
| Technical manual - 10Mb pdf, scanned original | Logic diagram - 1.4Mb pdf |
| Translated version - 10.8Mb pdf, completed August 2009. This manual has been reproduced from a 1972 Russian publication, we recognise the copyright of the original publisher. | |
| German Logic diagrams for the Soemtron 220 | |
| These drawings are courtesy of Bernard Green, they include component references and values, logic symbols and a diagram for each board. They give an insight into the what the logic designers were able to achieve in the functions of the Soemtron ETR 220 with such basic, albeit almost primitive electronics then available in 1960's German Democratic Republic. | |
| Gates | AND - OR Gates |
| Buffers - 1 | Buffers |
| Buffers - 2 | More buffers |
| Delays & FlipFlop inputs | Delays & FlipFlop inputs |
| Basic FlipFlops | Basic FlipFlops |
| Monostables | Monostables |
| Schmitt Trigger | Schmitt Trigger |
| Clock oscillator | Clock oscillator |
| Core driver | Core driver |
| Core sense amplifier | Core sense amplifier |
| Nixie tube drivers | Nixie tube drivers |
| Power supply | Power supply |
| And the boards - | ||
| Board 12 | Cathode drivers and number key encoding | |
| Board 11 | Anode drivers, digit position decoder function keys encoding | |
| Board 10 | Display digit position counter | |
| Board 9 | Memory Register addressing | |
| Board 8 | Negative result latch plus three other undefined | |
| Board 7 | Function latches | |
| Board 6 | Control gating | |
| Board 5 | Function to be determined, Clock oscillator | |
| Board 4 | "E" register, misc gating and drivers. | |
| Board 3 | "C" register | |
| Board 2 | Core Memory Read, Write and Inhibit drivers | |
| Board 1 | Core Memory and datasense amplifiers | |
| 1 | V.E.B. - - - - - - - - - - - - - | Volks Eigener Betrieb, or Peoples Owned Company | |
| 2 | Büromaschinenwerk - - - | Office Machine Works | back |
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