My first ZX Spectrum Composite mod.

So I’m up the ladder this morning, hands full and in the middle of repairing a small area of plaster coving when there’s a knock at the door. Typical isn’t it….I did think about ignoring it but you never know so after untangling myself from everything and trying not to spill my plaster I headed to the door. I’m glad I didn’t ignore it afterall, it was the postman delivering a few parcels too large for the letterbox. New (old) retro games and that replacement ZX Spectrum keyboard membrane I ordered a few days ago (quick service!).

So back in the temporary geek den this afternoon I’m fixing up two ZX Spectrum’s and made a bit of a discovery on another.

The replacement keyboard membrane appears to be much more robust than the original and the two connecting ribbons are a good inch longer and  less prone to snag when you open up the casing.


ZX Spectrum replacement keyboard membrane from



It’s an easy install, as this is just a drop in replacement and therefore only took a few minutes. A quick test and all is working good as new.



For the other Spectrum, I thought I have a go at composite modding.  As standard, all ZX Spectrums are fitted with RF modulators thus allowing them to work with the TV’s we had back in the 80’s. RF video is not exactly the best video quality therefore, with a a little modification, one can bypass the modulator and get a better picture via RCA Composite.

I had no idea how easy this was until the mystics of Google enlightened me.

Basically, you have to disconnect the 5v feed to the independent RF modulator circuit by cutting the wire I’ve marked in Blue. Cut it at the board end and not inside the RF box.

You also need to cut the video feed wire and the wire to the resistor near the RF input socket. Make both of these cuts inside the RF box. I’ve marked these in Red.

Take the cut end of the video feed and solder in a piece of wire between here and the little hole in the RF input socket. Marked in Yellow.




..and that’s it.

Connect a standard RCA cable to the RF (now Composite) and see if it works. No more fuzzy display.



Oh and that other little discover, it appear that one of my ZX Spectrum’s is one of the early 16k models.



4 responses to “My first ZX Spectrum Composite mod.

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