NEC Turbografx-16 and PC-Engine S-Video mod (schematic revision 2024)
0(Disclaimer: A Dazzle DVD Recorder HD was used to get the screenshots presented here. An actual CRT will have better quality than what is shown in this video.)
NEC Turbografx-16 and PC-Engine S-Video mod (schematic revision OCT-2024). Years back on the forums I had posted a simple schematic based on TheSteve's design. Over the years I had noticed there was flaws in the original design. Having not been able to test this modification on anything other than a Turbografx-16, Duo-R, and PCE-Duo at the time, it would be years before I could revisit it, this year exactly, and try it out on the Coregrafx II and white PC-Engine.
This way I could finally make sure the flaws were consistent across multiple models of the game system using the exact same mod. If you go by the original design by TheSteve, he called for a 220 ohm value to be used on luma. After heavy comparisons, it ends up that value produces just too dark an image, causing you to crank up the brightness settings on your monitor more than you should have to for certain titles. Installing a 175 ohm value on luma provides a brighter picture, getting closer to the composite video brightness.
In essence, you can see the trees in Dungeon Explorer easier, amongst other things. At this point, it would be a issue of preference. You could make it even brighter by dropping to a even lower value, like 160-150 ohm. But for me, 175 is the sweet spot where everything that should be visible on screen, is.
The other critical issue is shimmering was still present. This is because you actually need to follow the trace leading from Pin 40 on the HuC6260 to the first resistor you run into, and remove it. This will eliminate near all the composite related shimmer. A side effect of this though is that composite video will be disabled. To re-enable it, you will need to purchase and use a S-video to Composite adapter.
When it is all said and done, please remember when doing this mod, that YMMV. This system was not designed with S-Video in mind, so while yes, the image quality will improve a decent bit over composite, it will not be on the same level as like the Sony CX S-Video output in a Genesis model 3, or a Sega Saturn.