One of the most common faults on the ZX81 / Timex 1000 now is a non-working keyboard.
These are brand new (latest 2022 batch), very high quality self-adhesive replacement membranes with the benefit of modern design technology and clearer graphics.
They are more resistant to heat and UV light than the originals, so the conductive tracks will not deteriorate and crack as happened over time with the original membranes.
These membranes also suit the Timex/Sinclair TS1000 computer, but there are a couple of slight differences in the keywords printed on the keys between the ZX81 and the TS1000. The same meaning is the same though (Rubout instead of Delete for example).
