Like many machines of it's generation, the only output from the ZX81 is a UHF television signal. Analogue tuners in Modern TVs (if they even have them) don't like the approximation of composite video the ZX81 generates. Even more so the earlier version with the 2C184E ULA which is missing part of the signal.
The Future Was 8 Bit (on the right), which were a bit smaller, and didn't have the holes in. They were a better fit here as there are no connections on the back of the PCB, so I can just rest it on the original modulator circuitry. You could remove the original modulator PCB if you like, but there is enough space to just leave it in place but disconnected.
switch mode version.
16K internal RAM, and a new membrane fitted.
Timex Sinclair TS1000.
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