The Kenbak-1 computer


About the Kenbak-1


The Kenbak-1 was a commercially available computer from 1971. Years before the Altair, IMSAI, Apple etc. showed up.
Inventor was John V. Blankenbaker from California. It was created before any microprocessor was available. John had in 1971 a look to the first microprocessor shortly after creating the prototype but the first microprocessor could not improve the design.
The idea to build the Kenbak-1 was born in fall of 1970. By spring 1971 John Blankenbaker had the prototype built. All by himself from scratch. The computer is very educational and John wanted to sell the Kenbak-1 mainly to schools.

Judged the "first personal computer" in 1986 by a panel at the Boston Computer Museum (later the Computer History Museum San Jose) that included Apple co-founder Steve Wozniak. Published in the Computer Museum Report, Volume 17 — Fall 1986.
This makes the prototype Kenbak-1 the first of the first personal computer. A very emotional discussion goes on about the question of the first personal computer. The problem is, that ‘personal computer’ is not exactly defined. And many other computers were nominated by different people to be the first personal computer.
The Kenbak-1 is considered by the American Computer Museum to be the world’s "first personal computer”.
But anyway, it was the Kenbak-1 that was chosen by experts including Steve Wozniak. It was a remarkable step towards the computer revolution. The real computer revolution was not beginning with mainframes etc. used for business. The private use of computer started it all.

The American Computer Museum call it to be the world's "first commercially available personal computer". The Altair 8800 was later called the “first commercially successful personal computer”. A very good compromise. Later, other computer got different titles.

John V. Blankenbaker was one of the early computer entrepreneurs starting and working in a garage. He designed the computer and all manuals etc. by himself. The name Kenbak is obviously chosen from his last name Blankenbaker. Here is the story.
The Kenbak-1 was unfortunately sold only about 40 times. The personal computer revolution started years later. The story of the Kenbak-1 is one of those tragic stories in history. The company couldn’t afford to place more ads, for example in Popular Electronics. And so, the company was slowly running out of money.
Later the company was sold and the successor, the CTI Education Products Inc., including building material for many Kenbak-1. This company sold only a few Kenbak-1's.
This company never paid John Blankenbaker and eventually sent him back parts for some 45 Kenbak-1 as some kind of payment.

John advertised the computer only in the American Scientific magazine from September 1971 for two or three issues. Probably focusing on private individuals and advertising in the Popular Electronics magazine would have resulted in a much bigger success. Like it was for the Altair 8800 in 1975.

Today, only a few original Kenbak-1 still exist. Today only 14 machines are believed to exist worldwide. And only one revision A prototype was ever built. If the Kenbak-1 is considered the first commercially available personal computer, then the prototype is the very first ever.


Technical data

256 Byte serial memory (two MOS shift registers, each 1,024 bits) and 1 MHz clock speed, 132 ICs. Programming is done in machine language.


The name 'Kenbak'

The name "Kenbak" was derived from John V. Blankenbaker's surname. The full name was too long so a search was made for a subset of the letters.

John observed the consecutive set of letters "kenbak" was similar to "Kodak" with the beginning and ending "k's". George Eastman, the originator of that name, succeeded by making the camera affordable to every person. He wanted to do the same thing with the computer so he was happy to have a name suggesting the mass market.

John's wife warned him that there would be a spelling problem but he thought that if people could learn to spell Kodak then they could learn to spell Kenbak. His wife was correct. Many people wanted to spell the name as Kenback which is how it is pronounced.

The additional of the "-1" after the name Kenbak was to be prepared for the future models. The corporation, when it was formed, was called Kenbak Corporation.

The design of the computer and the instructional material were entirely his work. John was assisted by his brother Joe in laying tape on the mylar sheets which defined the logic board.

For most of the time that Kenbak Corporation was operating, John was the sole "employee" of the company.

Except for a few months, the operation was located in his garage.

Later the rights were sold to the CTI Educational Corporation who continued the work. Some of the computers, functionally equivalent to the original units, bear their name.


Differences between the prototype and the production units

Enter-Button The Kenbak-1 was never bread boarded or tested prior to the design of the mainboard. Remarkably John's design had only a few errors and just a few additional wires and other minor changes were required.
Only the prototype has a red enter button. This was changed for the production units and an additional switch was installed to protect against changing the program status. The production units have a slot in the front for a possible punched card reader which was never available. The legends below the switches were relocated for better reading.
Just a few changes in the design of the motherboard for the production units were necessary. The prototype got some hand-soldered additional components.
The case was colored by John Blankenbaker himself. He gave a sample of the color to the company that produced the production unit cases. For this reason, the color on the prototype is not consistent and scratches are more common.
The prototype has no serial number or labels. Production units started with serial number 167. John lived 12167 Leven Lane, Los Angeles.