Soemtron Downloads

Soemtron logo of unknown origin

As we accumulate drawings and information for the Soemtron 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 (C)2007 somtron.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 the intellectual property rights of the Soemtron ETR series calculators resides with V.E.B. Büromaschinenwerk Sömmerda (1) and their designers. The following list is a translation of the German component references and terms used that we have found so far.

Component / TermReferenceTranslation
ResistorWWiderstand
DiodeGRGleichRichter
Flip Flop Bistabile Kippstufe
Carry Ubertrag (UBER)
Write Schrieb
Quality standard1 - 3Güteklasse
Many thanks to Philipp Maier for the above translations.
Ferrite core driver Ferritekerntreiber
Measure or TestpointMPMessPunt
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. Component references for the circuits are prefixed by the board number or ancillary function, EG. for Board 7 Resistor 24 the reference is "7W24", "KW2" is resistor R2 on the Keyboard (resistors are Widerstand in German). Missing or left over components are left on each circuit diagram until the 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 26/6/2008
2 Display Display circuit updated 26/6/2008
3 Backplane Backplane circuit updated 26/6/2008
4 Board 12
Board 12
Cathode drivers and numeric key encoding circuit
Logic diagram
updated 15/7/2008
15/7/2008
5 Board 11
Board 11
Anode drivers and function key encoding circuit
Logic diagram
updated
updated
10/7/2008
15/7/2008
6 Board 10
 
5 bit display "Z" counter circuit
 
updated
 
26/6/2008
 
7 Board 9
 
F2,5-6 function latched circuits, including register addressing
 
updated
 
30/6/2008
 
8 Board 8
 
F1/3, VER and MZ function latched circuits
 
updated
 
26/6/2008
 
9 Board 7
 
B1-4, VOR and R function latches circuit
 
updated
 
26/6/2008
 
10 Board 6
 
Control gating circuit
 
updated
 
26/6/2008
 
11 Board 5
 
V, SCHRIEB, S1 function latches and 25Khz clock circuits
 
updated
 
26/6/2008
 
12 Board 4
 
Arithmetic unit E Register (input), Carry latch and digit drives 0/1 circuits
 
updated
 
9/7/2008
 
13 Board 3
 
Arithmetic unit A Register (output) and digit drives 5-9 circuits
 
updated
 
26/6/2008
 
14 Board 2
 
Core memory drivers and decoding circuits
 
updated
 
9/7/2008
 
15 Board 1
 
Core store, read amplifiers and digit drives 2-4 circuits
 
updated
 
26/6/2008
 
16 Supply Power supply circuit To be designed  
Complete circuit All current circuits for the Soemtron 220 (4.88Mb file) updated 15/7/2008
Complete logic All current logic diagrams for the Soemtron 220 (357Kb file) updated 15/7/2008
220 net list Net list for the Soemtron 220 circuits updated 15/7/2008
Snagging list Current problems with the circuits for the Soemtron 220 updated 10/7/2008
 
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) Silicon Diode  
 
Russian Technical Manual for the Soemtron 220
These manuals are courtesy of Gerhard Just, including a basic description of the logic elements, their component values, operation and even a timing diagram or two.
Technical manual  - 10Mb pdfLogic diagram  - 1.4Mb pdf
 
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.
GatesAND - OR Gates
Buffers - 1Buffers
Buffers - 2More buffers
Delays & FlipFlop inputsDelays & FlipFlop inputs
Basic FlipFlopsBasic FlipFlops
MonostablesMonostables
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 to be determined, 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 datasense amplifiers 
  1. V.E.B. = Volks Eigener Betrieb, or Peoples Owned Company.      back
  2. Büromaschinenwerk = Office Machine Works.      back