Gadget Master

We like to hear about retro-East German electronics on Gadget Master - see Hans' Nixie clock takes a step back in time - and here is another, the Soemtron Calculator.

Thanks to reader Bernard Green for sharing this story about an electronic calculator without a single integrated circuit that was designed and built in East Germany in the 1960's.

Not only this, he emphasises, the designers achieved all the functions with few components - there are only 31 flip-flops in the machine and some very intricate logic in order to keep component count as low as possible. Compare this to modern designers for whom minimisation of design has become a lost art, he says.

Bernard's employer in 1967 imported this machine, he tells us, and he was a senior service engineer for it, which included being sent to the factory for a 10 week training course, where he greatly admired the design.
 
He highlights this retro-marvel but also has two requests: Does anyone...

* Have any knowledge about finding the connectors? (see picture below)
* Know of any trace of an ETR 221 (the two part printer version)? 

He writes:

This one arrived here as a Christmas present from a fellow enthusiast in Germany. The first I have actually owned and I intend to get it working again. The problem is I need to build the test box which is a set of lamps that monitor all the flip flop states and several other signals. This box also provides a slower or manual clock pulse as at 25Khz the machine work too fast to see the operation of individual parts. Building this is not the real problem, as it is just a high impedance input and lamp driver per signal. The problem is locating the necessary plugs that mate with the top two sockets in the second picture. The pitch is 3mm and they would have been made by an East German factory in the 1960's
 
Cannot find any trace so far.
 
Also a second hunt is under way. Mike would like to locate a Soemtron ETR 221 which is a two part machine. The keyboard and printer in a case like to 220 but without a display and the basket of printed circuit boards were in the other part. The two parts connected by an umbilical cable. But as far as is known the one we had in London may have been the only one that was made.
 
When the Wall came down and Germany re-united many of the factories and companies of the old German Democratic Republic shut down and few records remain available. So maybe one of your readers may have some knowledge or even a few of the connectors. After all we did find a person who had in a cupboard a few of the micro-switches used in the keyboard.

More info on the Soemtron can be found at www.soemtron.org, a UK site run by one Mike Hatch, mentioned above, and an admirer of the Soemtron desk calculators.

As a post script, Bernard also describes a happy trip to Sömmerda:

The credit has to go to the engineers who designed that machine. We met some of them last September when I made a sentimental visit to Sömmerda and Mile Hatch came to look at the only known ETR 224 in the museum. Not only did the museum make us their guests for the day, and arranged for 7 retired Soemtron engineers to meet us. The big surprise was when Mike was offered an ETR 224 from a private collector, one of the Soemtron engineers.