How do I make a CPC-RGB DIN to RCA -RGB or Composite cable?

[DistantStar001]

Much as the title says: I have an Amstrad CPC464 with its matching monochrome monitor/PSU. However, I want color! Unfortunately, whenever I Google or search eBay for options all I get are SCART adaptors, and if you couldn't tell from my spelling of the word color, I'm in the U.S. Thus SCART compatible monitors aren't really a thing out here, and importing a color Amstrad or SCART enabled monitor is kinda cost prohibitive. So I need a means of connecting what I have.

I do have several PAL capable monitors. And at least two of them have RGB inputs. However, they use 3 RCA inputs designed to receive the sync signal on the Green input. This has not been a problem for my Spectrums, PAL Commodores, or BBC Micro, but all of those have composite. 

The issue is that all of the pinouts that I've seen separate the sync and luminance signals on separate pins. Which, as far as I can tell, an RCA input will need both. But on which line???

If anyone has built this cable before, assuming it's possible at all, I would appreciate some instruction or maybe a schematic laying out all of the connections. 

[DistantStar001]

OK. working from a pinout pictured I found on Google [I would post it, but I haven't figured out how to on this forum yet], I have been able to workout a 6 to 5 pin adaptor using jumper wires and a headboard that will allow me to use a 5-pin DIN to 4-line RCA cable to breakout the red, green, and blue signals. Luminance and synch are routed to the Green line since that's where the monitor is expecting them. This gives me Blue and Red as expected, but no Green. Also, the text is pink which makes sense since yellow should be a combination of green and red. I've tried just using luminance or sync and while I still get a signal, green is still absent. 

Interestingly, eliminating the Green line to the monitor (keeping luminance and sync) causes the text to go Red. So I think the Green signal is there, but it appears to be getting washed out, or is weak for some reason.

Any ideas on how I can get a proper green signal?

[McArti0]

You need an rgb-sync to rgb COMPONENT ( not composite) converter.

https://stoneagegamer.com/retrotink-rgb2comp-convert-scart-rgb-to-component.html

Or

https://www.amazon.com/s?k=scart+to+ypbpr+converter&crid=2VVXNLE1LBN1F&sprefix=scart+to+yprbp%2Caps%2C278&ref=nb_sb_ss_sc_1_13

[pelrun]

There's no such thing as "rgb component". Component is YPbPr. It definitely won't be the correct thing to feed into an RGB+Sync On Green input.

[dodogildo]

Order a RGBtoHDMI kit by Meesse. It provides the best possible picture from a CPC on a modern display. It's surprisingly not popular in this forum but I'm using it (and its C64 sibling) for a long time with much delight.

https://www.sellmyretro.com/offer/details/rgbtohdmi-for-amstrad-cpc-464~~664~~6128%2C-bbc~~master~~compactand-black-spectrum-%2B2~~%2B3-61524

[McArti0]

Component is YPbPr. It definitely won't be the correct thing to feed into an RGB+Sync On Green input.

I assumed that the guy was wrong. But if you're right and he wasn't wrong, then after connecting the luminance to G+sync there should be a green image.

[ZorrO]

Lumina is needed only for monochrome monitors. RGB don't need Lumina. Only R,G,B, Synch and GND. Each of them on separate cable. Try by multimeter is it really separate.
TV with scart use Lumina to switch from Composite into RGB. But color monitors don't need Lumina.
You says you have RGB PAL monitor so, what problem? 
Try connect for this monitor something else with RGB, for example Amiga, if colors are fine, that mean monitor is OK. So bug is in cable or in CPC. But if cable is fine, you have first CPC which can't show green color.

[retro space]

I think the US version of the Commodore 1084 might be suitable. You have one? It does not have SCART or RCA RGB in the uS, but it does have a DIN RGB input. With  RGB and Sync pin, just like the CPC, only different arangment.

[pelrun]

It appears combining sync and green is pretty trivial, the simplest approach just uses a capacitor and a resistor.

https://www.raphnet.net/electronique/sync-on-green/sync-on-green_en.php

[DistantStar001]

I think I figured it out. I got a decent offer for an MP-1 PSU/RF Modulator. From what i can see, it uses the same modulator found in the BBC Micro, Acorn Electron and ZX Spectrum, so I should be able to do the same A/V mod (cut the power to the modulator, the modulator to the jack, and then reroute the video via a 100mf capacitor to the jack). As I understand it, composite conversion will be handled by the video board in the unit.

Maybe once I have it, I can examine the circuit and workout a standalone board to give me component or S-Video, but for now, this should work.

[eto]

I think I figured it out. I got a decent offer for an MP-1 PSU/RF Modulator. From what i can see, it uses the same modulator found in the BBC Micro, Acorn Electron and ZX Spectrum, so I should be able to do the same A/V mod (cut the power to the modulator, the modulator to the jack, and then reroute the video via a 100mf capacitor to the jack). As I understand it, composite conversion will be handled by the video board in the unit.

Maybe once I have it, I can examine the circuit and workout a standalone board to give me component or S-Video, but for now, this should work.

Maybe this helps: 

The MP-1 mod is documented here: https://www.cpcwiki.eu/index.php/LCD_And_Plasma_TV_Solution#Converting_an_MP1.2F2_to_Composite

And the section below shows a RGB-to-Composite circuit. 

[Bryce]

You can convert the RGB to composite using this circuit: https://www.cpcwiki.eu/index.php/RGB_SVideo
Unfortunately I don't have any of these left, but I think there were some other users here, who also built and sold them.

Bryce.

[DistantStar001]

Maybe this helps:

The MP-1 mod is documented here: https://www.cpcwiki.eu/index.php/LCD_And_Plasma_TV_Solution#Converting_an_MP1.2F2_to_Composite

And the section below shows a RGB-to-Composite circuit.

Yes, thank you! This is exactly what I was looking for.

If I'm understanding this correctly, and having looked up the MC1377 data sheet, the CPC isn't putting out a true PAL signal? as from what I can see, frame-rate is determined from the in-circuit oscillator and NTSC/PAL output is selected by grounding/floating pin-1.

I'm gonna guess that stepping up to a 60Hz signal would be problematic, but my Commodore 1702 can process a 50Hz image, it just can't do PAL color, so a 50Hz NTSC color signal should allow me to use a CRT.

Something to consider if I want to replicate the circuit. Also, it might be compatible with my BBC as the only difference I can see is that it puts our +5v where the CPC puts out luminance.

I suppose I could add a switch, but i don't like making permanent and visible mods to vintage equipment.

You can convert the RGB to composite using this circuit: https://www.cpcwiki.eu/index.php/RGB_SVideo
Unfortunately I don't have any of these left, but I think there were some other users here, who also built and sold them.

Bryce.

I've seen this, but couldn't figure out where to get it. As for replicating it, the schematics are there, but the AD724 is surface mount, making it a bit difficult to experiment with on a breadboard.

[retro space]

Maybe this helps:

The MP-1 mod is documented here: https://www.cpcwiki.eu/index.php/LCD_And_Plasma_TV_Solution#Converting_an_MP1.2F2_to_Composite

And the section below shows a RGB-to-Composite circuit.

Yes, thank you! This is exactly what I was looking for.

If I'm understanding this correctly, and having looked up the MC1377 data sheet, the CPC isn't putting out a true PAL signal? as from what I can see, frame-rate is determined from the in-circuit oscillator and NTSC/PAL output is selected by grounding/floating pin-1.

I'm gonna guess that stepping up to a 60Hz signal would be problematic, but my Commodore 1702 can process a 50Hz image, it just can't do PAL color, so a 50Hz NTSC color signal should allow me to use a CRT.

Something to consider if I want to replicate the circuit. Also, it might be compatible with my BBC as the only difference I can see is that it puts our +5v where the CPC puts out luminance.

I suppose I could add a switch, but i don't like making permanent and visible mods to vintage equipment.

You can convert the RGB to composite using this circuit: https://www.cpcwiki.eu/index.php/RGB_SVideo
Unfortunately I don't have any of these left, but I think there were some other users here, who also built and sold them.

Bryce.

I've seen this, but couldn't figure out where to get it. As for replicating it, the schematics are there, but the AD724 is surface mount, making it a bit difficult to experiment with on a breadboard.

Get those tiny SMT to DIP boards. They are making things very easy.