Hi,
A little PCB to check the ZX81's sound input from "The Plotter", By M.J. Raymond.
Kicad r.8 project/Gerber:
http://zx81.ordi5.free.fr/brico/loadmeter/
LOAD-Meter by M.J. Raymond [PCB-Kicad]
LOAD-Meter by M.J. Raymond [PCB-Kicad]
Xavier ...on the Facebook groupe : "Zx81 France"(fr)