Sinclair Black Watch
In 1975, Sinclair Radionics launched one of the world's first digital watches. There is no question that Sir Clive Sinclair is one Britain's greatest modern age inventors. Inventing products such as the first digital calculator and an early pocket cathode ray tube pocket television. Sinclair was ahead of his time in many respects.
The Black Watch is another great example. Unfortunately, the watch had more than its fair share of technical gremlins. It is written that the time ran faster in summer than it did in winter and the date feature "required adjustment only five times per year" - according to the watch's instructions. The battery was rumoured to last a full ten days. There was a running joke that more watches were returned for repair, than were manufactured. Don't forget that this was the mid 1970's, where silicon technology was in its infancy and nobody had even heard of the term Electromagnetic Compliance. Electrostatic discharges was the stuff of science fiction movies. Wearing a nylon shirt could spell disaster for the watch.
Silicon Cortex has taken delivery of one of the watches that should have been repaired, but wasn't. We've taken it apart to assess the design and spot any obvious damage. Anyone who has been lucky enough to take apart a Sinclair ZX81, will know that the printed circuit board inside is hand drawn with curvy tracks. Unlike today's straight tracks of today's boards. The circuit board in the Black Watch is approximately 25x25mm and has curvy tracks. There is a five digital 7-segment LED display (some models have four digits), one timer integrated circuit chip, a crystal, a small capacitor and a variable resistor for calibration. It was possible to buy the watch as a kit for the hobbyist to assemble.
Sinclair Radionics did offer a service to finish assembling a watch if the user had trouble. The fixed charge then being £8, which equates to £60 today. Our intention at Silicon Cortex is to the restore the watch that we have, to full working order. We've checked the assembly and there are no dry joints. Therefore we will remove and reuse the display and flexi-assembly onto a newly designed board by us. The integrated chip on the board has been obsolete for many years, so it will be replaced with an ARM core processor and a real-time clock chip. The 1970's technical problems aside, the Sinclair Black Watch is an icon piece of British technology and we are looking forward to showing off the finished article in a few months time. This story continues on our Twitter site @Silicon_Cortex.
Lawrence Blackwood
Silicon Cortex