Prototype

Prototype (John1)

This was the first Kenbak-1 computer made by John Blankenbaker. He did not construct a breadboard. He went straight from the paper design to the printed circuit (PC) board. This didn't work as is, he had to debug and modify it significantly. This was different in many ways from the later computers:

The power supply board generated +5 volts, -5 volts, and - 12 volts to power the logic board (in later computers the power supply only supplied +5 volts and -12 volts, and then a large dropdown resistor and zener diode on the logic board generated the -5 volts for the shift-register memory.)
The front panel was simpler and lacked a "lock" switch. The "store" button was a red "ENTER" button.
Many jumpers, and trace cuts were needed. A transistor, a capacitor, and two diodes were added to get it working.
He used one intel 1404a, and one 1404 (without the a-suffix) while other machines only used 1404a shift register memory.

We thank to the current owner, Achim Baqué of Western Germany, for permission to use some of his photos for this gallery. Visit his web site at thefirstpc.com for much more information.

Right click on the image and select "open image in new window" for a full size/resolution photo.

Front

1023 x 682 From auction in 2015, copyright retained by Bonham's. See Bonham's Auction website for photo https://www.bonhams.com/auction/22964/lot/76/kenbak-1/

Top/Left

4124 x 2478 From auction in 2015, copyright retained by Bonham's. See Bonham's Auction website for photo https://www.bonhams.com/auction/22964/lot/76/kenbak-1/

Top/Interior

3222 x 2020 From auction in 2025, copyright retained by Bonham's. See Bonham's Auction website for photo https://www.bonhams.com/auction/22964/lot/76/kenbak-1/

Top/Left/Interior

4007 x 2312 From auction in 2015, copyright retained by Bonham's. See Bonham's Auction website for photo https://www.bonhams.com/auction/22964/lot/76/kenbak-1/

Interior Board

1920 x 1152 courtesy of Achim Baqué

Top/Interior

1920 x 957 courtesy of Achim Baqué

Front

1920 x 546 courtesy of Achim Baqué

Bare Board

1920 x 1279 courtesy of Achim Baqué

John holding the Prototype

1200 x 1671 courtesy of Achim Baqué

John with Prototype 2

1492 x 750 courtesy of Achim Baqué

John running the Prototype

1468 x 1315 courtesy of Achim Baqué

Front (older)

492 x 153 c/o J. Blankenbaker

Older interior

552 x 331 c/o J. Blankenbaker

Grandaughter w/ prototype

396 x 297 c/o J. Blankenbaker

Sales Catalog

1700 x 2200 listing when for sale in 2016 by Jeremy Norman. See the original catalog here: https://www.historyofscience.com/pdf/55.pdf

Power Supply

1920 x 625 courtesy of Achim Baqué. This is different from the power supplies used on the Rev A and Rev B production machines, as the -5 volt supply was output, instead of being generated on the logic board.

Panel Switches

1920 x 862 courtesy of Achim Baqué

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