soemtron.org - Soemtron ETR Series Calculators Gallery

Gallery

Soemtron Calculators Gallery

The Soemtron 220 ........
Many thousands of Soemtron ETR 220's were made during their production run and by modern standards they are large and cumbersome, but very typical of their age - the 1960's. This section shows a few views of a typical Soemtron ETR 220 in good condition owned by calculator collector Serge Devidts.Click an image for a larger version.
	Inside view	Decimal point selection	Nixie tube display close up
Pictures ©2007 Serge Devidts, used with permission, for more see his site here.

The Soemtron 221 ........
Following a chance comment by Bernard Green, 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 ETR 221. Bernard had suggested the existence of just such a machine, having recently said that he recollected seeing a two part unit shipped into the UK whilst he was at Office and Electronic Machines in London. The 221 is a printing version of the 220, but split into two parts: a desktop unit with keyboard and printer mechanism, and an ancillary unit (floor or desktop ?) with the main electronics (and power supply ?). So far only one of these units is known to have existed, that unit shipped to Office and Electronic Machines.Click an image for a larger version.
Early model ETR 221		Picture ©2009 Serge Devidts, used with permission, for more see his site here.

The Soemtron 222 ........
Manufactured from 1970 to 1972 by V.E.B. Büromaschinenwerk Sömmerda, about 3,000 Soemtron ETR 222's were built during the two year production run. The processing logic of the Soemtron ETR 222 calculator, derived from the ETR 220, is all transistorised.Click an image for a larger version.
	Inside view	Pictures ©2007 Ruediger Kurth (Robotron) Used with permission.

The Soemtron 224 ........
With just over 500 machines built in a six year period, again by V.E.B. Büromaschinenwerk Sömmerda, the ETR 224 is now a very, very rare machine. Only three are known to exist, two in the museum in Sömmerda and one in our collection. The processing logic of the ETR 224 is believed to be derived from the 222.Click an image for a larger version.
	Pictures ©2009 Ruediger Kurth (Robotron), Used with permission. and ©2009 www.soemtron.org	Inside view

Various photos of our Soemtron 224 before restoration
Photos of the restoration progress.

The Extender Card ........
Test equipment for the Soemtron machines is very unlikely to be found, indeed in discussions with engineers from the old Soemtron factory on a recent trip to Sömmerda it transpires that the factory and contents are long gone. To this end we are designing our own test equipment, and the most useful at the moment is an extender card.Click an image for a larger version.
Extender board	Extender board socket	Extended board	Board and extender

Soemtron 220 production ........

Two photos here show a Soemtron 220 production line from the book "BWS Sömmerda", by Annegret Schüle, (ISBN 39-8039-311-9, or ISBN 978-3-9803931-1-9) published by DESOTRON in 1995. Dr. Günter Hartmann of DESOTRON has kindly given us permission to use these images from the book.

The two photos (left) below show an ETR 220 production line, with the left side of the production line appearing to be operators checking each machine, whilst the right side appears to be a row of technical checkout or diagnostic stations. Each station has an oscilloscope and a "Prufgerat" or test box beside it to aid in de-bugging. The Soemtron Prufgerat was a custom designed piece of equipment that plugs into a pair of diagnostic connectors inside the machine, all three models of the ETR range had these test connectors, and we suspect that there were panel overlays for the test box to show the differing flip-flop arrangements between the models. An ETR 220 panel layout can be seen on page 185 in the Russian Technical Manual on the "Downloads" page. Interestingly each ETR undergoing test appears to be in a master carrier frame, it's not known at this time if this was just to assist in moving the units around or if they were actually used for electrical connections in the test process. The third photo is of a couple of prototyping boards, the topmost one being for the ETR 22x series calculators and other machines that Soemtron produced using the same PCB form factor. space Click an image for a larger version.

Soemtron 220 production

Prototype boards

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