My computer history
3. 1982 I progressed to the ZX Spectrum which was £99, because I couldnt afford the BBC computer which was £399 in 1982!!!
I created Spectrum 3000, marketed by DK'tronics and made about £200. (Previously made for the Sinclair ZX81)
I had a lot to do with the ZX spectrum which involved the OPUS discovery disk drive system, which was brilliant!
user guide is here
dissembly of the
ROM (text file format)
The Circuit Diagram is below
The Opus disk drive, designed for the Spectrum
OPUS circiut diagram , not drawn by me