"NVG Catalogue - Circuit Diagrams"

Software title FTP path & filename
Disciple circuit diagram
pics/circuit-diagrams/disciple.gif
Kempston joystick interface circuit diagram
pics/circuit-diagrams/kempston.gif
Plus D circuit diagram
pics/circuit-diagrams/plus_d.gif
RGB interface circuit diagram
pics/circuit-diagrams/rgb.gif
ZX81 64K upgrade circuit diagram
pics/circuit-diagrams/zx81-64k-upgrade.gif
ZX81 circuit diagram. Part 1
pics/circuit-diagrams/zx81-circuit1.gif
ZX81 circuit diagram. Part 2
pics/circuit-diagrams/zx81-circuit2.gif
ZX81 clock doubler. Diagram & details
pics/circuit-diagrams/zx81_clock_doubler.zip