Composite and S-Video question

[strattsp]

I have been searching around unsuccessfully for a solution to my problem. Please forgive me if it is a basic or trivial problem, I am an ME, not an EE.

I am modding a colecovision for composite and s-video output. I want to offer both.

right now I have:


chroma ________________________s-video
____________________/
\__________________
\_________composite
luma __________________/
____________________/
\________________________s-video

I am getting a lot of interference in both signals. I am only testing one signal at a time. I can understand why I'm getting interference in the s-video signal, but why would this give me interference in the composite signal?

More importantly, how do I fix the problem?

Thanks,
Steve

 

[MacGyverS2000]

Are you just tying the chroma and luma signals together directly or are you using caps?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[strattsp]

no cap, just tying the two together

 

[MacGyverS2000]

You need a cap in the chroma line... without it you're going to get the color burst signal bleeding into the luma signal. Figure something in the 1nF range should be good.

Dan - Owner

http://www.Hi-TecDesigns.com