Clive Sinclair And The Small Home Computer Revolution
Written by Harry Fairhead   
Tuesday, 22 July 2014
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Clive Sinclair And The Small Home Computer Revolution
From calculator to computer
ZX80 and beyond


So much of the recent history of computing concerns what happened in the US. Companies like Apple grew to dominate the world but in the UK a surprisingly large number of smaller home computer companies sprang up.  Just as the US had Silicon Valley the UK had Silicon Fen - a high tech area based around Cambridge.

The problem is that it is tempting to think that electronic innovation started with the personal computer and is typified by IBM's launch of the PC or Apple's launch of the iPhone. The early days of the home computer were a direct continuation of the tradition of building innovative gadgets that were otherwise out of reach using nothing but regular and easy to get parts. This was the maker movement in the 1960s, but of course we didn't call it that then. The future home computer designers were building radio sets, transmitters and boxes that flashed lights just for the fun of it. 

The entire enterprise was limited by the lack of funds and the high cost of electronic components. As a result projects were either small or there had to be ingenious ways of doing what seems to need 50 transistors or other devices with only five.




In the early eighties the UK electronics industry was vital and vigorous - and much of the reason was a single individual - Sir Clive Sinclair.



Clive Marles Sinclair, born 1940


Clive Sinclair was born in Surrey, the oldest of three children. His father was an engineer and from an early age he showed an interest in applying science and technology. He designed a calculating machine that used punched cards and binary and was very disappointed to find that someone had thought of his "original" idea before!

He was keen on mathematics which must have helped him understand the electronics that so fascinated him in his teenage years. All the signs of what he was to do in later years were there for anyone to see. He built miniature radios, amplifiers and a communications systems for his hideout in the woods. This was all in the days when electronics was just shifting from valves to transistors.

Another indication of the future was the way he worked hard at part time jobs. Some were menial, like cutting grass and washing up, but he did apply for a summer job with Mullard - a large component manufacturer.

He was rejected for being too advanced in electronics theory for his years!

Still this didn't put him off. His first article for Practical Wireless, a magazine that was mostly about building different types of radio and assoicated devices, was published while he was still at school and must have indicated to him that electronics could lead to both money and fame.

Although good at school he left at 18 - convinced that the right thing to do was to start an electronics company. This may seem like an obvious thing to do in this age of multi-million dollar startups but back then only big companies did anything with electronics or technology.

C.M. Sinclair's Micro Kit Co was the result. A single transistor radio kit was sketched out in an old exercise book and costed on the next page. The technology was easy but the cost of advertising was a shock. How to raise necessary money? Why not write more articles for Practical Wireless? This he did but the publishing delay still left him without immediate cash - so he applied for the job of editorial assistant.

For a while he was effectively the editor of the magazine in all but title. Then he moved on to work for a small technical publishing outfit, Bernard Babani, writing technical books. Babani's publishing company produced (and still does) lots of technical books at amazingly low prices.

Sinclair produced book after book. The first was "Practical Transistor Receivers Book 1" and the last "Modern Transistor Circuits for Beginners" in May 1962. They all sold well and if you look at any of the circuits they contain you can see that he had a grasp of transistor design that was well ahead of the average. On the other hand the rate of production was so high it was suspected by some that he never actually built the circuits described!




His designs also showed his ingenuity at work. By making one component do more than one job he could cut the component count down - so reducing the size, cost and often power consumption.

He still wanted to start his own company and finally in 1961 got round to registering the name Sinclair Radionics Ltd but he still lacked capital. On the promise of financial backing he left Babani - only to discover that the money did not materialise.

He got another publishing job as technical editor of Instrument Practice. This was a good move as it gave him the opportunity to see all the new components he wanted - including getting hold of samples.

His first money making venture started when he discovered that Plessey were making high quality transistors - Micro Alloy transistors, MATs - and were throwing away the ones that didn't meet the design spec. He tested these rejects and found that they worked well enough to be used for some things.

He bought reject MATs in boxes of 10,000 for 6d each (about 45p or 85 cents) and resold them for 7/9d and 8/6d depending on quality - markup of more than x15.

He wrote another Babani book - 22 Tested Circuits using Micro Alloy Transistors - what a marketing ploy!




The next step was to produce a kit. This turned out to be a tiny amplifier packaged into less than a 1 inch cube. At the time it was amazing and it packed components in vertically so tight that there wasn't a space to be seen. 

It was a success and more followed. Nearly all made a virtue of miniaturisation. At the time, although transistors had reduced the size of electronics and made it portable, most companies were not trying to make miniature products. Just building a circuit using transistors gave a sufficient size reduction to be impressive so why try any harder.




Sinclair on the other hand seemed to have a vision of what electronics would be like in the future and he wanted to make it happen instantly. To achieve this he had to design exceedingly clever circuits and find novel ways of mounting them on printed circuit boards to make the best use of space.

This sort of design does produce the smallest possible products but it can also make them difficult to actually produce and very difficult to fix. At first this didn't matter so much because they were being sold in kit form. An experienced constructor can cope with, and even enjoy, the challenge of getting a kit to work!

The kits continued to be produced. The Micro-6 radio smaller than a match box, the TR750 power amplifier and a range of pulse width modulated PWM amplifiers. Apart from being impossible to make work, the PWM amplifiers were the first excursion Sinclair Radionics took into digital electronics.




All of the kits were advertised in Sinclair's own instantly recognisable style. They made people want to own the product - they were exciting and all part of achieving the right image. This image extended to the first range of non-kit completely finished products, a range of Hi-Fi products impressed the enthusiasts with their modern looks.

In 1970 Sinclair Radionics moved in to a huge building, The Mill, on the banks of the Great Ouse. The company had grown from a seller of kits to a manufacturing company. It was also large enough to allow Sinclair to start to indulge his interests - or should that be obsessions. He wanted to build a tiny TV, and research on suitable tubes was started.

But what has all this got to do with computers? It should be said at this early stage in the story that Sinclair is not first and foremost a computer man. To him electronics was analog first and digital only much later.

At first his impact on the world of computing was almost incidental.





Last Updated ( Tuesday, 12 August 2014 )

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