CGA video cards worked at the same frequencies that TV, so you could try to connect (almost) directly your CGA output to a SCART/Peritel/Euroconector input (i.e.: a cheap TV set). There are some schemes on internet, but not all of them works (it seems that designs based around 74ls86 or 74hc86 works).
Also, you may put some OA and "add" RGBI signals, to make a crude greyscale signal, and made four outputs:
- Direct RGBI signals (full color).
- Greyscale feed to R, G and B (greyscale).
- Greyscale feed only to G (green).
- The fourth output would be an amber output, but I don't know how to get a realistic amber (nobody remember amber phosphor monitors?).
Also, with such a device you would only get green colours, but no persistence. And with my experience with some Sinclair Spectrums and a CPC, you'll get very big and clean pixels... maybe using the composite output will help you to get a more "fuzzy" image (with a 32 inch TV, the pixels are really BIG; but with a 15 inch TV set and some blur, they'll look "better").
Those thoughts are valid only if you're using a CGA card... EGA modes have different frequencies and won't get picked by a TV.
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