View Full Version : Question about S-video, composite, Y, B-Y and R-Y
12-18-2009, 05:26 PM
I am trying to make my ColecoVision, a PAL unit, to output either S-video or composite.
The usual easy guides refer to a chip in the RF unit which isn't there on the PAL unit, and a different RF unit too - the RF unit on PAL is just a stack of resistors, etc but no chip.
The graphics processor, TMS9918 I believe it is, outputs Y (luma) and also B-Y and R-Y. Would combining R-Y and B-Y make Chroma (S-video) or is there another way? My electronics knowledge isn't great, so any help would be appreciated please - easy diagrams etc please! At the moment I have a ColecoVision in bits I can't use.
12-18-2009, 06:58 PM
Would combining R-Y and B-Y make Chroma (S-video)I don't know the specifics of the hardware you're talking about, but assuming this is component video as you describe it (and now that you mention it, I have heard of ColecoVision component mods before now) - no, you won't get a correct S-Video chroma signal from combining component red+luminance and blue+luminance lines. S-video chroma uses NTSC/PAL colour space, for starters.
In terms of off-the-shelf ease you'd probably be looking at a component->RGB converter and then RGB->S-Video, or just straight component->S-video if you can find something suitable. You'd have to be pretty competent to build your own, but it should be feasible if you could find a suitable PAL/NTSC encoder and were willing to put in the time. My guess would be that this isn't "easy diagram" territory, but I might be wrong.
EDIT: had a quick scout around, saw someone suggesting that a cheap way would be a set-top box with component in and S-video out, like a DVD recorder. Also that if you want to make your own, you might want to look at this chip (http://www.nxp.com/pip/TDA8501_CNV_2.html). There was a diagram to go with it but the site is down.
12-18-2009, 10:28 PM
So, does that mean I can wire the ancient console to cables immediately, and connect to a modern television via component? (will I need to boost the signals, if so how, or are they fine as are?) If that is the case, do I connect Y and ground to one cable, B-Y and ground to another cable and R-Y and ground to a third cable? (normally cables seem to use two connections, outer wires as ground and the inner wire to the signal). If I can prove that the system works on component, I can then find a way to migrate the signals into composite, S-video or RGB if I can.
All comments and help appreciated!!
I really want to play my ColecoVision and can't at the moment. I tried to use the RF originally but it didn't work / signal too weak (and I don't want RF anyway).
This is an interesting article. Will hook up the B-Y, R-Y and Y from the console to my new television and see what happens...
12-19-2009, 03:54 PM
I need some help please.
The chip suggested: TDA8501 - datasheet is HERE (http://www.datasheet4u.com/html/T/D/A/TDA8501_PhilipsSemiconductors.pdf.html) (click on "locate datasheet") for the PDF file
I don't mind if I get composite, RGB or S-video output; I do want it in PAL though (is that pin 17 > ground?). What I need to know please is do I just connect the R-Y, B-Y, Y lines from the Coleco graphics chip to a 47uf capacitor (each line) to the pins on the TA8501 and then tap S-video off the luma and chroma lines off that chip, and job done; or do I need to do other things too please/need other components (if so, how connected?).
I am tearing my hair out at this! I get audio fine, just can't get video!
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