ZX Spectrum 48K S-video modification


I found the following schematic on worldofspectrum.org when searching for a way to improve the picture quality on my ZX Spectrum 48K:

User redhawk668 on worldofspectrum has taken the schematic further and designed a few revisions of a PCB to replace the RF-modulator. You can find them at github or buy the latest revision from tindie.

Having the components available and jumping the gun early, I went with the REV A board. M2 screws hold the PCB in place. The screws also provide the ground signal and therefor added locking washers and some solder to make sure there is a good connectivity.

I had a problem with disappearing picture when entering the DivMMC menu on my ZX Spectrum Issue 3 board. Observing the signal with an oscilloscope I could see the sync signal dropped when entering the menu. This is not related to the S-Video board. Using the same board on an Issue 2 board resolved the issue.

First part of the video is with composite video(dot crawl), second part is the same machine with the S-Video modification.