The Soemtron Calculator Collection

Our refurbished Soemtron 220

and it's original condition !

The Soemtron brand of calculators encompassed three and possibly four calculators, the 220, 222, and a printing calculator the 224. Contemporaneous literature of the period does describe and show a type 221 printing calculator believed only to exist as a publicity release (see December 2009 below) in the Büromaschinen Lexikon, a German publication of the 1960's.

This website is dedicated (in probably a very nerdy way !), to the Soemtron electronic calculator range and came into existence when an old piece of equipment was received in 2007 from Prague in the Czech Republic, after a Google search for "core memory" 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 top covers (see the bottom picture). After a few days research and translating some German text off of the baseplate, we worked out what this old dirty corroded hulk was - a Soemtron ETR 220 calculator, which turns out to be a very interesting piece of early electronic calculator history from 1960's and 70's German Democratic Republic.

A typical Soemtron ETR 220

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

The third picture (left) is of a very good condition Soemtron ETR 220 owned by calculator collector Serge Devidts, for more information see his website here

Time line -
Older news from soemtron.org can be found here.

Typical connectors

February 2010 - Following the great help visitors to this site have given in the past, we are now looking for some connectors - can you help ?. The photo (right) shows a typical set of connectors used on the Soemtron calculators in 32, 20 and 11 pin sizes of both male and female types. The main body of these connectors would appear to be porcelain, although the black link plug (2nd from the top in the photo) is a plastic material. The 1mm diameter pins are on a staggered three row format at 2.5mm pitch (to be confirmed), and they "float" in the connector housing allowing a small amount of re-alignment on insertion.

These connectors were apparently a special standard to the Robotron brand, cable connectors in both plug and socket versions were available and can be seen here (top of page) listed as the "Daro20" and "Daro32". connectors. We think however, that they may have been available elsewhere, as we have seen similar connectors used in the British MOD on electronic systems, where they had sheet metal back shells with a floating external cable clamp (Pye or Plessey comes to mind). A few years ago there were articles on the web about the 40th anniversary of the invention of the mouse by Doug Engelbart, which used the same style of connector, see this page at Tech-E-Blog.

If you know anything about or have any information on the Robotron "Daro20" and "Daro32" connectors please contact us here, or email . We are looking for a male / female set of the "Daro32", and a male / female set of what would be "Daro11".

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A Soemtron 221 Picture ©2009 Serge Devidts Click for a larger version.

December 2009 - After some research by Bernard Green and ourselves, about a possible ETR 221 unit, a recent email from Serge Devidts has confirmed the existence at some time in the past of a two part printing calculator, the ETR 221. Bernard had suggested existence of the 221 a while back having said that he recollected a unit had been shipped into the UK whilst he was at Office and Electronic Machines in London. He described the 221 as a two part machine: a desktop unit with keyboard and top mounted printer, and a second unit connected by an umbilical cable to the main electronics section. The only reference to this split personality machine was a vague picture in the Büromaschinen Lexikon for 1967-68, however the receipt of Serges' picture (right) has shown both sections of a 221 connected by an umbilical cable and large connector.

Click here for previous events in the Soemtron website time line.

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 -