Zuse – Computer
restored by the
Konrad Zuse Schule in Hünfeld,
Computer Museum History Center
in Mountain View (California)
May 1, 1999
On April 30, 1999 19 students of the Konrad Zuse Schule (Konrad Zuse School) in Hünfeld, where Konrad Zuse lived from 1956 till his death in 1995, finished the assembly of the historical Computer Z23 of the Zuse KG for the delivery to Computer History Museum in Mountain View (California) close to San Francisco. Computer History Museum is a part of the Boston Computer Museum.
Picture 1: Mountain View (Mtn. View), where the Z23 will be delivered lies south of the San Francisco Bay, a little bit south of Palo Alto.
The students of the Class 11 IT of the Konrad Zuse Schule in Hünfeld restored together with the class teacher Bubenheim and Leopold Stein, who is a member of the Konrad Zuse Gesellschaft, the historical Z23 computer. The next picture shows the Z23 in 1961.
Picture 2: The Zuse Z23 Computer (1961), which was delivered 98 times to universities and industry.
The development of the computer Z23 began in 1958 by the Zuse KG and the first Z23 was delivered in 1961. The Z23 was a further development of the approved Z22 in transistor technique. The Z23 decreed about a magnetic drum, a ferrit core memory and expensive periphery. The logic structure of the Z23 was similar to the Z22. The Z23 was delivered with an ALGOL 60 compiler. The user of the Z23 were almost the same as with the Z22. Applications areas were machine building, ship building, electrical engineering, electronics, hydro and gas dynamics, reactor physics, ballistics, geodesy, optics, energy supply, traffic technique, mining, administration, government, universities, chemical production, boiler construction. The Zuse KG delivered 98 machines till 1967. The Z23 computer was a machine consisting of 2700 transistors and more than 600 diodes. It was a very successful machine for the Zuse KG. The price of the Z23 was 200 000 DM in 1961.
The next picture shows Konrad Zuse with the Z23 in 1980.
Picture 3: Konrad Zuse (1980) with the Z23 in the rear, where the power supplies can be seen.
The next picture shows a computer center with the Z23.
Picture 4: Computer center in 1963 with Zuse Z23 computers.
We now present the story how the students restored the Machine Z23.
2 The Story of Restoring the Historical Zuse Z23 Computer by the Konrad Zuse Schule
Professor Dr. Hermann Flessner (Hamburg), who is a member of the Konrad Zuse Gesellschaft, was the initiator of the Project Z23 in order to deliver the historical computer Z23 to USA. He created the contacts with Mr. Shustek of the Boston Computer Museum. This museum transferred some of his exhibitions on the history of computing from Boston to the west coast (Mountain View).
Picture 5: Professor Dr. Hermann Flessner.
Leopold Stein, also a member of the Konrad Zuse Gesellschaft, organized and advised the students how to build up the many pieces of the Z23. Leopold Stein also will build up the Votis Software Museum in Hünfeld in the near future.
Picture 6: Leopold Stein, who lives in Hünfeld.
The next picture shows the Class 11 IT of the Konrad Zuse Schule (Konrad Zuse School, which is a vocational school) in Hünfeld, who restored the Computer Z23.
Picture 7: The students of the Class 11 IT of the Konrad Zuse Schule, who restored the Zuse Computer Z23. Left: The class teacher Bubenheim.
The students of the Class 11 IT of the Konrad Zuse Schule in Hünfeld wrote a booklet about the assembly of the Z23. They created the following cover for this booklet.
Picture 8: The booklet of the assembly of the Z23 created by: Lars Buecher, Stefan Eyrich, Angelika Happ, Thomas Nelhübel.
In the Foreword of the booklet we can read amongst others (Translated by Horst Zuse into English): In February 1999 the Konrad Zuse Gesellschaft asked the Konrad Zuse Schule, whether it is possible to restore the historical computer Z23, which was built by the Zuse KG from 1961.
It was a wish of Konrad Zuse, that one of his computers should be set up in a museum in the USA. The Class 11 IT under the leadership of the Teacher Bubenheim agreed to build up the Z23, which single pieces where set up in a store in Hünfeld.
At Monday, March 1, 1999 the pieces of the Z23 were delivered with a truck. By beginning of this project, the whole class visited the Konrad Zuse Abteilung in the Stadt- und Kreisgeschichtlichen Museum in Hünfeld (Konrad Zuse Section in the native museum in Hünfeld). There, another Z23 computer has been set up. At March 3, the class begun to restore the Z23.
The next picture shows the Z23 computer in the Konrad Zuse Abteilung in the Stadt- und Kreisgeschichtlichen Museum in Hünfeld (Konrad Zuse Section in the Native Museum in Hünfeld).
Picture 9: The Computer Zuse Z23 in the Konrad Zuse Abteilung in the Stadt- und Kreisgeschichtlichen Museum in Hünfeld (Konrad Zuse Section in the native museum in Hünfeld).
The following students with the class teacher Bubenheim helped to restore the Z23:
- Christian Becker
- Dieter Befort
- Lars Buecher
- Stefan Eyrich
- Peter Göbel
- Stefan Göpfert
- Angelika Happ
- Sebastian henkel
- Jens Jagusch
- Alex Keller
- Patric Matuszewski
- Adam Miozga
- Christian Most
- Thomas Münkel
- Christopf Naderer
- Thomas Nelhübel
- Michael Pachowski
- Manual Päsold
- Holger Rohde
The students made a lot of pictures of the Z23 in the Museum in order to understand the architecture of this machine. Firstly the heavily soiled Z23 had to be cleaned.
Picture 10: The boxes of the Z23 had to be cleaned up and to be set up.
Picture 11: Here pieces with printed circuit boards, which were mounted with transistors and diodes had to be cleaned up.
The students saw the first time transistors, resistors, capacitors, diodes and a real wiring.
Picture 12: The printed circuit boards of the Z23.
On the rear the printed circuit boards were wired in a very complex way.
Picture 13: The wiring pattern of the Z23.
There was a special device in order to check the printed circuit boards.
Picture 14: A device in order to check the printed circuit boards. They were plugged in the slots.
To install the magnet drum of the Z23 was one of the most difficult tasks.
Picture 15: In this box the magnetic drum with a capacity of 8192 words a 40 bits has to be installed.
Picture 16: The magnetic drum of the Z23. The capacity was 8192 words. The rotation speed of the drum was 6000 rotations per minute.
The engine on the right side is a transformer from 380 Volt alternating current to direct current. The engine also equalized fluctuation of the electric power.
Picture 17: The printed circuit boards have to be installed. They were mounted in revolvable doors.
Picture 18: The control and arithmetic units of the Z23. The Z23 had an operation time of 10000 additions per second. The clock frequency was 150 000 Hertz.
On the top of the arithmetic unit the power supplies have to be installed. The power consumption of the Z23 was around 4000 Watt.
Picture 19: Power supply of the Z23.
Picture 20: The input device of the Z23.
Picture 21: The input device of the Z23 operated by an employee of the Zuse KG in the sixties..
Picture 22: Two students try to understand the functionality of the many pieces of the Z23.
Picture 23: The design plan for the printed circuit boards.
With respect to the picture above the students write very humorousness in their booklet: This circuit has been solved too much inconvenient. We can bridge over the jumper 384 plus the capacitor, then we have to connect it with the rectifier, and then we can double the clock frequency of this machine.
Picture 24: Two students put together the boxes of the machine.
Picture 25: A part of the power supplies of the Z23.
Picture 26: The power supplies of the Z23 for the input device.
The most sophisticated unit of the Z23 was the ferrit core memory with a capacity of 256 words a 40 bits.
Picture 27: The ferrit core memory of the Z23.
On Friday, April 30, 1999, the work to restore the T23 was finished. Of course, this event had to be celebrated.
3 Friday, April 30, 1999 in Hünfeld
At Friday, April 30, 1999 Mr. Helmut Käsmann, who is responsible for public relations in Hünfeld, invited the following guest and TV-Stations in order to present the work of the students of the Konrad Zuse Schule for the public.
- Hünfelder Zeitung
- Computer Magazin Konrad
- Computer bild
- Bild Zeitung
- Radio FFH
- Hessischer Rundfunk
- SAT 1
- Pro 7
The following persons were invited for the celebration and the following press conference. They thanked the students, teachers, etc. for their excellent work:
- Studiendirektor Stefan Schmitt, who is the director of the Konrad Zuse Schule in Hünfeld welcomed the guests.
- Prof. Dr. Hermann Flessner, who initiated the project to deliver the Z23 to USA, explained the wish of Konrad Zuse to get a machine of him to USA.
- Dr. Horst Zuse explained the importance of the Computer Z23 in the sixties and thanked the students and teachers for their excellent work.
- Dr. Wilhelm Mons, the acting Chairman of the Konrad Zuse Gesellschaft, presented the task of the Konrad Zuse Gesellschaft.
- Angelika Happe, a student of the Class 11 IT, presented very humorousness the work of the students. She said, that they are very sad to give away the machine Z23. It is a real big computer, which is totally different related to a motherboard of a PENTIUM Processor.
- W. Vogt, a member of the city council (The major of Hünfeld Dr. Eberhard Fennel could not come), thanked the students and teachers for their work.
Pictures of the finally restored Z23 and the press conference will follow in some days here.
I am very grateful to the students and teachers of the Konrad Zuse Schule, to Prof. Hermann Flessner and Leopold Stein, who made it possible to restore a Zuse Z23 computer for the delivery to Computer History Museum in Mountain View in California. We now show the Class 11 IT with their teachers, again.
Picture 28: The Class 11 IT with their class teachers Bubenheim (right) and Mr. Fey (left). Mr. Fey is the head of the IT (Informationsverarbeitende Assistentenausbildung: Education of assistants for computer science).
I talked with the students and they listened very curious to my explanations how the Z23 worked. They asked me how the ferrit core memory worked and how this memory was constructed. In order to make them more curious to the history of computer development of Konrad Zuse but also in US I gave every student the Konrad Zuse Multimedia Show. There, the following picture can be found.
Picture 30: Constructing a ferrit core memory in the Zuse KG in 1961.
I also thank Dr. Leonard J. Shustek very much for his agreement and effort to exhibit the Z23 in the Computer Museum History Center. Prof. Dr. Flessner, Leopold Stein, Dr. Wilhelm Mons and me will go to the inauguration of the Z23 in Mountain View. We also will invite one student of the Class 11 IT to come with us to Mountain View.
At April 21, 1999 I proposed to the Konrad Zuse Gesellschaft to rebuild the Computer Z3 again. The Konrad Zuse Gesellschaft agreed to this project and the project will be realized by Horst Zuse, Wilhelm Mons and Leopold Stein. It also will be supported by some other persons and the Konrad Zuse Schule in Hünfeld. Because the students of the Konrad Zuse Schule in Hünfeld are educated in precision mechanics, the following unit could be rebuilt by the students.
Picture 31: The punch tape reader of the Z3.
Having rebuilt the Z3 computer again, we can show students and persons the first working computer of the world on exhibitions, etc.
Horst Zuse, May 1, 1999