The Xerox Alto was the first computer designed  to support an operating system based on a graphical user interface (GUI), later using the desktop metaphor.

The first machines were introduced on 1 March 1973, a decade before mass market GUI machines arose.

The rat-infested Digibarn monitor isn’t even meant to be connected to an Alto, and does not work either. But we find a way to retrofit it to the Alto, and find that a tiny light bulb buried in the high voltage circuitry is the cause of the failure. More details about what a bulb is doing in the circuit on Ken’s blog (and don’t believe the inane comments, it is NOT used a fuse):…


All of the switching power supplies from our Xerox Alto from the Digibarn are bad. All of them! And the main LH Research MIghty Mite 5V/60A power supply is putting up a real fight. By the time I start this video, we are a good week into troubleshooting it, with a growing pile of bad parts and no end in sight.

Following restoring… was last modified: November 14th, 2017 by admin

Also published on Medium.

CC BY-NC-SA 4.0 Following restoring… by admin is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.


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