What is the 'correct' S-Video circuit for the CXA1145?

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FBX
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What is the 'correct' S-Video circuit for the CXA1145?

Post by FBX »

I'm interested in modding my Genesis consoles (model 1 VA2 and VA3 NTSC) to support S-Video output. When I research this subject online, I'm finding this seems to be a subjective interpretation from one person's mod kit to the next. One schematic I looked at made use of transistors on both Luma and Chroma output of the CXA1145, while another only used a transistor on the Luma line. I need somebody like Voultar ( or Voultar himself LOL ) to give me the straight scoop on what exactly is needed for the Luma and Chroma output pins of the CXA1145 for properly converted and attenuated S-Video output.

Much appreciated!
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ChuChu Flamingo
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Re: What is the 'correct' S-Video circuit for the CXA1145?

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Ryoandr
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Re: What is the 'correct' S-Video circuit for the CXA1145?

Post by Ryoandr »

CXA1145 S-Video will always be approximate because the 1145 isn't made to drive Y/C output, unlike 1645, 2075 or MB3514.
That said, I had good results with this method. But you'll most probably get some jailbars.
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FBX
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Re: What is the 'correct' S-Video circuit for the CXA1145?

Post by FBX »

Ryoandr wrote:CXA1145 S-Video will always be approximate because the 1145 isn't made to drive Y/C output, unlike 1645, 2075 or MB3514.
That said, I had good results with this method. But you'll most probably get some jailbars.
That was one of the circuits I looked at. I'm thinking about going with that one since it came from viletim. I found SMD rated equivalents of all the parts to see if it's possible to make an SMD-based PCB with no through-hole components. Surprisingly it is possible, but just barely.

At any rate. While the 1145 doesn't properly drive S-Video on its own, the circuit to boost it doesn't necessarily have to be 'approximate' in design. There should be a 'correct' way and everything else 'less correct', as I would expect the Y and C outputs of the 1145 to be fairly similar from chip to chip.
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