Probably the youngest don’t now this, but in the early 1980s, there were some personal computer initiatives like Apple II (Apple Computers, 1977), PET (Commodore International, 1977), TRS-80 (Tandy Corporation / Radio Shack, 1977) that already dominated the international market.

This was made possible by the very first Altair 8800 (Micro Instrumentation Telemetry Systems, 1975) and its clone IMSAI 8080 (IMS Associates Inc, 1975). The current standard computer is a direct descendant of the IBM PC 5150 which would only be released in 1981.

Until that moment, most hobbyists and enthusiasts had only seen a computer in magazines or inside universities and companies – and we are talking about other countries! In Brazil, a market reserve was created during the military government period, which encouraged the strategic market for national computers.

It was in this scenario that in 1980 in England, Sinclair Radionics – a company that created innovative yet inexpensive devices, creator of the first pocket TV and pocket calculator in the western market – became Sinclair Computers. His objective was exactly the same: to embark on the innovative technology of the moment, but at a low and affordable price. This not only allowed the access of a large part of the population to the world of information technology, but also allowed to produce a cheaper computer even here in Brazil.

In the brazilian market reserve, many companies cloned computers and sold what was possible: We had clones of Apple (CCE, Unitron, Miamar, Microdigital), Sinclair (Microdigital) and MSX licenses (here for sharp and gradient).

I learned to program on a Tk82c (brazilian ZX81 clone). It was my first computer (and first in my home). So, I decided to try to reassemble this computer from scratch – the whole project. The ZX80 came with the design scheme in the manual but the ZX81 implemented a good part on a single chip (rare today – it is no longer manufactured) in order to make the project cheaper. On this website ( http://searle.x10host.com/zx80/zx80.html ), Grant Searle (an English electronics enthusiast) describes the original project and the expansion for the ZX81 – the same expansion that was used by microdigital in the initial clones.

My goal is to study the basic electronics of computers and reproduce it. I chose the ZX80 for its affective value but also because it is very simple to understand and reproduce. The objectives of the project are:

• document the process in a simple way
• develop fixes and improvements
• create a kit for other enthusiasts
• develop secondary parts like keyboard and case
• document and develop expansions among those launched
• … Learning and having fun with all this adventure.

In honor of my old TK82c that provided everything else…