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2650 Mark I   An article in the April 1977 edition of the magazine Radio-Electronics changed my life. With its two following articles in May and June, it described how to construct a microcomputer. It detailed not only the construction but also the theory of operation. At right is shown the page header of Part II of the article from the May 1977 issue of the magazine.


Up to then, I had only known mainframes. Here was an article on how I could construct my own personal computer.

My father had constructed several valve (tube) audio amplifiers and this is where my interest in electronics started. His most ambitious project was to create what was then called a radiogramme. Today we might call it a stereo except that it was only mono. It was, for its day, a hi-fi multi-band radio and 78 r.p.m. record player. He even built the wooden cabinet. It was a good looking piece of equipment but the radio part did not have good sensitivity.


This problem of encountering under-performance at radio frequencies (RF) was something that also dogged me. In the 60’s, I took out a radio-control licence and built a radio-control transmitter. While it should have had a range of at least several hundred yards, it disappointed me by working only over a distance of about three feet! At that time I did not have the equipment or the expertise to correct its faults.


What immediately engrossed me in the microcomputer article was the way that digital electronics seemed to do away with the analogue problems of RF. Providing one had a good power supply and added some bypass capacitors, the thing just worked. This was an enormous step forward.


I immediately immersed myself in learning about TTL (Transistor Transistor Logic) chips by reading books and by buying a few used chips and experimenting with them. At the same time, I studied the Radio-Electronics articles with every spare moment until I understood how every part of the circuit worked. I was so interested in this that I even took the stuff with me on holiday, much to my wife’s dismay. After a couple of months I felt that I understood the circuit well enough to start changing it to my own design, still without having built anything. Eventually, though, I got down to building it using the wire-wrap  method on S-100 boards. My the end of the year I had spent over $350 on books, parts and other paraphernalia. Remember, this was in 1977 dollars.

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