General Category > Amstrad CPC hardware

RGBI to SCART RGB for popular line doublers

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matty72:
Help, need a correctly wired 6128 Scart cable cable to suit popular line doublers (OSSC or Retro Tink 2xSCART)

My issue is that I can't find a Scart cable with appropriate circuitry to convert the RGBI+S (4 bit color) out of a 6128 to RGBS, I.e. using the LUM pin 6 to change intensity of the RGB color so that 2 shades of 8 colors (16 color) results.
I don't believe an active (powered) cable is required for the stated line doublers as they both expect RGB input.

My guess is that the inner circuitry could simply be a voltage divider between LUM pin and each RGB line, I'd like your input.
I'm not aware of Amstrad modifying any of the colors as Commadore did (yellow became brown), please inform me otherwise.
Can anyone point me to a pre-made cable or a decent/correct wiring diagram?

llopis:
For what it's worth, I'm able to feed the output of a CPC using a regular SCART cable into OSSC and it accepts the signal perfectly fine. I didn't have to convert it to digital RGB plus two bits of luminance.

pelrun:

--- Quote from: matty72 on 13:57, 14 September 20 --- RGBI+S (4 bit color)
--- End quote ---

No, there's no conversion needed, because the CPC monitor output is *not* digital colour at all! R, G and B are full 3-level analogue, and LUM is just the (unused) monochrome video signal for the greenscreen monitor. Since LUM also has the composite sync signals present, it can be used directly for that purpose if your input isn't too fussy. If it is fussy, you'll just need to feed it through a sync stripper.

Bryce:

--- Quote from: matty72 on 13:57, 14 September 20 ---Help, need a correctly wired 6128 Scart cable cable to suit popular line doublers (OSSC or Retro Tink 2xSCART)

My issue is that I can't find a Scart cable with appropriate circuitry to convert the RGBI+S (4 bit color) out of a 6128 to RGBS, I.e. using the LUM pin 6 to change intensity of the RGB color so that 2 shades of 8 colors (16 color) results.
I don't believe an active (powered) cable is required for the stated line doublers as they both expect RGB input.

My guess is that the inner circuitry could simply be a voltage divider between LUM pin and each RGB line, I'd like your input.
I'm not aware of Amstrad modifying any of the colors as Commadore did (yellow became brown), please inform me otherwise.
Can anyone point me to a pre-made cable or a decent/correct wiring diagram?

--- End quote ---
The CPC LUM signal is derived from the R,G and B signals, so tying this signal back to the RGB signals externally would just be providing endless positive feedback (essentially going in circles) and every signal would instantly saturate resulting in a white screen. Even if it did work (by limiting the levels or whatever) you'd end up with some really wierd colours that would be far from what a CPC should look like.
Why would you want to do this? The RGB values already represent exactly what the colour mixture should look like.

Bryce.

ComSoft6128:
I'm using scart cables from Cool Novelties for a 6128 and a 6128 Plus to the OSSC and they work fine for most uses......BUT (yes there always is one) - some demos and games will NOT display correctly using this setup.

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