Here’s a small blog on prepping your old 8-bit ZX hardware to do some retrogaming: on fixing keyboard membranes, creating a composite video signal and using the DivMMC Enjoy! cartridge to ease your storage life.
But before that first a word on Internet sellers of second hand Sinclair computers. You should be aware that a reknown problem of the ZX keyboards is that the membranes die in the course of 20 years. If you happen to stumble upon a ZX being sold on the internet, always ask them to check the keyboard. I’ve bought three computers the past few weeks, and ALL of them had worn keyboard membranes. But only one seller reported this before finishing the deal! The other’s claimed “it worked before I shipped it!”. Yeah right. Not in a million years, buster! However, I fixed them like this: