Need Help to Add an S-Video Port to my FS-A1 MKII

If you want internal mod I guess it would make sense to look at FS-A1WSX’ schematics as this has built in S-Video

Tip: Since this machine has the same CXA1145 TV-Encoder as the Sega Megadrive, you can also look for tutorials on how to add s-video on that console too.

Sadly, not all TVs have an easy way to add RGB. Yes, you can always bypass everything and inject on the neck PCB, but this has a plethora of problems of its own, including signal level, insulation, autocalibration and even the loss of brightness/contrast controls.

I have a Sony Trinitron 14" (Sony KV-1450B), a model that looks very similar to the one featured on the famous Sony HB-F1XV ad on MSX-Magazine. But that whole family based on the CXA1871S Jungle chip is a nightmare to add RGB input. Even if you try to bypass and go for the neck PCB, the main PCB senses it and shuts down the CRT as a protection.

It's somewhat possible to add component-video input to that family of TVs, but it requires a huge surgery and you'll have to compensate for the luma/chroma delay of the TV's Jungle Chip. Definitely not for the faint of the heart.

I ended up choosing a compromise: It's much easier to add s-video to this family. The 14" Trinitron model requires an extra PCB with a analog multiplexer that was only present on the bigger siblings, but once it's added it works like a charm. Since the original contrast and image quality of this TV is superb, the s-video input achieved impressive results.

(Note: ironically, it's very easy to add digital RGB input to this family. But that would only be relevant for PC-88 and FM-7 owners)

In a nutshell, buying a CRT to mod it to add RGB inputs is a lottery. I would advice to google for models that are easy to mod.