- Soemtron ETR Series Electronic Calculators

Soemtron ETR220, click image for a larger version, ©2007 Serge Devidts
Soemtron ETR220
©2007 Serge Devidts

Manufactured by V.E.B.[1] Büromaschinenwerk[2] Sömmerda, the Soemtron branded range of ETR22x[3] calculators encompassed three variants, the ETR220, ETR222 and ETR224 (a model with printout capabilities).  A possible fourth calculator, the 221, was seen in various sales literature of the period and does show and describe the type 221 printing calculator, but it is believed now to have only existed as a single machine for a publicity release (December 2009) in the Büromaschinen Lexikon[4], a German publication of the 1960's.  That one machine was possibly the one delivered to Office and Electronic Machines (OEM) in London, the UK importers.

Soemtron ETR222, ©2007 Serge Devidts, click image for a larger version
Soemtron ETR222
©2007 Serge Devidts

Welcome to the only complete collection of Soemtron model ETR22x calculators, a collection which came into being after an old piece of equipment was received from Prague in the Czech Republic, following a Google search for "core memory" one day during some research into the PDP-7 range of computers manufactured by the now defunct Digital Equipment Corporation.  The unit duly arrived, but it was found to be in a very poor state, dirty, rusty and missing its power supply and covers (photos).  After a few days more research and translating some German text off of the baseplate, we worked out what this old dirty corroded hulk was - a Soemtron ETR220 calculator, which turns out to be a very interesting piece of early electronic calculator history from 1960's and 70's German Democratic Republic.

Currently only four Soemtron 224's are known to remain in existence, click image for a larger version, ©2009 Rüdiger Kurth
Soemtron ETR224
©2009 Rüdiger Kurth

Over time we have conserved our original Soemtron 220 and eventually we hope to get first piece of Eastern Bloc calculator history from the 1960's into full working order, once we can get a suitable power supply into her.  Bookmark this page and come back from time to time and see how we are getting on.  We have now published and are updating full circuit diagrams (ein schaltplan) of the machine and its inner workings for those of you who are interested - not many probably !, but there again this is the Internet, so we hope you drop by again soon.

The two topmost pictures above are of a very good condition Soemtron ETR220 and an ETR222 owned by calculator collector Serge Devidts, for more information see his website.  The bottom picture is of an ETR224 printing calculator, a very rare machine as only 526 units were built, whilst there were over 150,000 ETR220's.

Timeline -
Older news from Soemtron.

December 2016 - Copies of three engineering manuals for the ETR220 have recently been received from Germany.

  1. Is a short extract of an unknown document (not item 3 below) with component placement drawings and track connections for the 12 main PCB assemblies.  Download (13.6Mb).
  2. Part two of a 1974 technical instruction manual, with board layouts, logic diagrams, circuits, assembly drawings and setup instructions.  Download (28.8Mb).
  3. A 1975 manual showing again the 12 main PCB assemblies but also including sub assembly drawings of the other major parts of a 220 including the keyboard, display, decimal point position switch, power supply and bypass regulator.  Part lists of the assemblies are given together with their Soemtron part numbers.  Download (18Mb).
  4. Derived from the documents above, a list of all Soemtron part numbers current available to us - Download (35Kb).

August 2014 - There has been a dearth of news for the Soemtron website for some time now as other things in life needed a little attention.  So to catch up -
Our main line of progress has been on the 224 and to update the website to current HTML5 spec where possible.

We have essentially completed the mechanical re-building of the 224 printer mechanism to the extent that it works reasonably well when manually triggered, but some re-alignment is needed to the print wheels and their rest position.  Work in the last six months has concentrated on decoding the circuitry of the twelve electronics boards in the card cage, to the extent that we now have a full, but unchecked circuit for the 224.  Currently we are working to resolve the temporary signal names (TMP-xxx) that were used in the circuit tracing and to find solutions for the problems in the 224 snagging list.  For further details see the ETR224 page.

August 2011 - An email from another of our contributors Rocco Thiel has turned up two Soemtron brochures from the 1960's, one for the ETR220 and one for the ETR221.  The ETR221 brochure is especially welcome as we thought that publicity information about this machine did not exist.  Each brochure can be found on their respective machine pages, or here 220, and here 221.

Fourth Soemtron 224 found, click image for a larger version
©2011 Rüdiger Kurth
(Click image for a larger version)

May 2011 - Another 224 found.  In an email to Bernard Green, Rüdiger Kurth another of our contributors, has written to say that he has found another Soemtron 224 machine as part of an exhibition in the Museum für historische Bürotechnik Naunhof (Museum of Historical Office Technology in Naunhof) - website.  The machine was apparently made in 1969 and is serial number 32549.  Close examination of Rüdiger's photo shows it is the same build version machine as we have in our collection, which is serial numbered 32612 and also from 1969, this brings the number of Soemtron 224 machines currently known to exist to four.

Previous events in the Soemtron website timeline.

The Soemtron 220 range also appeared in the "Büromaschinen Lexikon", a German publication covering office machinery and products.  Soemtron branded products appeared in the 1962/63 to 1968/69 issues, but only three are available online below -

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1 Wikipedia entry for V.E.B. = Volks Eigener Betrieb, or Peoples Owned Company V.E.B. [back] [top]
2 Büromaschinenwerk Office Machine Works [back] [top]
3 ETR Elektronischer
Tischrechner [back] [top]
4 The index page for the Büromaschinen Lexicon
4a A Soemtron 220, and a 221 with integral printer 1966-67 (then click the  "Soemtron" link)
4b A Soemtron 220, and a version with printer 1967-68 (then click the  "Soemtron" link)
4c Description for the Soemtron 220 and a "fast printer", click the "Sumlock" link to see photos and pricing for the 220 and 224. 1968-69 (then click "Soemtron" & "Sumlock" links) [back] [top]

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