[Help] No image but Sync with SEGA Megadrive and MultiMega

[BuckoA51]

Buy your cables from reputable sellers and they will be clearly marked RGB. Internally if you open one you can check that things are wired correctly as per http://members.optusnet.com.au/eviltim/gamescart/gamescart.htm

[SegaFanboy]

You use a simple AV-cable with a scart Adapter. Your cable has audio left, audio right and video. So all of your video goes through the yellow wire and it can’t be RGB. There are many good tutorials on youtube which explain what exactly RGB is. You should really watch them and try to understand the basics 🙂

In your case the OSSC gets the audio from the red and white cables. It also gets a composite video signal from the yellow wire. The OSSC is expecting a RGB signal and is happy to get a composite video signal to synchronize the red, green and blue inputs from RGB – which don’t exist. So you get sync, but no video.

For you SNES, try this
https://www.ebay.com/itm/Super-Nintendo-SNES-RGB-SCART-EURO-HQ-Cable-for-PAL-consoles-LUMA-for-SYNC/173327423400?hash=item285b1e97a8:g:tv4AAOSw2s1Urv5E
or this
https://www.retrogamingcables.co.uk/nintendo/super-nintendo/super-nintendo-pal-rgb-av-scart-cable-lead-cord-for-sale

whatever is cheaper shipping to France.

Your Mega Drive is a different problem. I don’t have a French one, the only thing I know is that the French Megadrive does not have a composite video output. So your Chinese cable does not work, because it tries to sync RGB with that output. The French Megadrive is different in some ways and I don’t exactly know in which.
Problably a Csync cable works, but i’m not sure about this. If not just look for mods or get a PAL one.

[Sean B]

This is an interesting problem. After a bit of searching, I found this thread https://assemblergames.com/threads/the-csync-on-genesis.53583/

As said above, the French mega drives don’t have Composite video (AV port pin 3) connected. They do have Csync (AV port pin 7) connected. Cheap 3rd party cables use Composite video for sync so your new cable wouldn’t work. As mentioned before, u need a quality cable which is wired for Csync. These cables from retro gaming cables https://www.retrogamingcables.co.uk/games-consoles/sega/mega-drive-1/sega-mega-drive-1-sega-genesis-1-sega-master-system-1-rgb-av-scart-cable-tv-lead say they are suitable for French mega drive and also OSSC. There is also a stereo audio version of the cable for better experience. They also have good info on RGB video and the difference between Composite video and Csync, for your information.

[NoAffinity]

Very high-level idea here, but could you not lift or sever pins 3 and 7 at the multi-out, then route the pin 7 circuit to pin 3? Voila, csync at pin 3.

this is taking into account zero actual details of performing this mod, just an idea. But curious, if it couldn’t solve the problem and save you from having to buy another cable.

[Sean B]

That is one solution. There are 3 solutions that I can think of.

1. Purchase the cable mentioned above.
2. Rewire the 3rd party cable so that pin 7(console end) connects to pin 20 (scart end)
3. Connect a wire from pin 11 (cxa1145) to pin 3 (AV port). A wire should already be soldered from pin 11 (cxa1145) to pin 7 (AV port) on the French mega drive so the wire can simply be moved.

It all depends on what the op feels comfortable with.

[PX2]

Thank you all for your suggestions and detailed info about the cables and signal types, glad to see that we can get the issue moving 🙂

Hopefully this weekend I will have some time to take apart one of the SCART cables I purchased, I want to check the wiring, try what “NoAffinity”and “Sean B” suggested and follow the diagrams provided by “BuckoA51”.
If that works then I will purchase quality cables which should definitively fix the issues.

I will keep you posted

[paulb_nl]

That official Sega RGB cable should work. At least if it works directly connected to the SCART input of the TV.

You can try to set Pre-Coast and Post-Coast to 3 in Sync options. Some Sega consoles need that.

[Author]

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