Advice for N64 Fra RGB Sync over composite video ?

[Nico128]

Hi

I have a N64 Fra modded for RGB with a official SCART. Sync is over composite video, and the quality of the image isn’t very good. There is a kind of “x” pattern.
OSSC improves a little bit the quality. But the “x” pattern isn’t totally removed.

Unfortunately I can’t use Sync over Luma because N64 Fra doesn’t output S-Video (only the N64 Eur).
I think using this cable could be better (it contains a sync separator LM1881). I’m goging to order it.

Does someone here owns a N64 Fra RGB, has the same problem, and can give me some advises how to solve it ?
Does someone knows with which parameters in OSSC I can play in order to decrese the effect of this “x” pattern ? Analog sync LPF is set to 2.5MHz. With scanlines it is also a better, depending of the game (it hides a little but the pattern).

Thank you

Ps: the pattern is totally removed on this picture with OSSC but I didn’t capture the whole screen. In some areas, the pattern still remains.

[BuckoA51]

I’d be surprised if just sticking a sync stripper in the cable will make any difference. What you probably need is a cable with better shielding.

[Nico128]

Hi. Thank you for your message. I forgot to copy past the link for the cable, that’s make my first message confuse The seller gives some explainations “Wired for composite sync aka CSYNC (with built in video sync separator LM1881 chip)”.
https://www.retrogamingcables.co.uk/nintendo/gamecube/NINTENDO-GAMECUBE-RGB-SCART-CABLE-COMPOSITE-SYNC-CSYNC

Does someone here know where I can buy a good cable ? Retrogamingcables seems to be the reference. I don’t know if someone has already tested. Cables from Ebay are all the same.

[paulb_nl]

If you are now using the offical PAL SNES RGB scart cable then that PAL Gamecube cable will result in a too bright picture. Using a cable with a sync separator is not recommended.

The best cable at Retrogamingcables is the Packapunch fully shielded cable. https://www.retrogamingcables.co.uk/nintendo/super-nintendo/packapunch-pro-super-nintendo-entertainment-system-snes-rgb-av-scart-cable-pal

You will need to ask them to make a cable with Composite video sync without sync separator because they only list it with Csync(LM1881) and Luma sync.

RetroRGB made a video comparing shielded vs unshielded cables and showed that with a shielded cable with Composite video sync you will not see the diagonal bars. https://www.youtube.com/watch?v=HV2cSKhO6v0

[Nico128]

Thank you for the video! I’m going to buy fully shielded cables (also for my Snes and GC), I’m happy to see that the problem can be solved.

Do you think the quality of a cable with Csync(LM1881) will be worst than sync over composite video ? I will ask Retrogamingcables, what he think.

[paulb_nl]

The quality should be the same with fully shielded cables but you have a higher chance of issues(sync loss) with the LM1881.

[Nico128]

Ok!

He replied me “Unfortunately we don’t have the SCART PCB’s to make the non-CSYNC at the moment. We will be getting more in a few weeks.”

[megari]

With the French N64 model, there is also the option of pulling CSYNC from the S-RGB A chip (pin 18). This could be connected to the unused Luma pin of the multi-out connector and you could use a sync-on-Luma cable. You just have to keep in mind that Luma is supposed to be a maximum of 1 V peak-to-peak (or was it 0.7 V, actually?), while CSYNC is TTL (5 V peak-to-peak), so you need to drop the voltage. Also, you should avoid pulling too much current from the S-RGB A pin. A resistor with the proper specifications should do the job in practice, but you may want to do something more sophisticated for various reasons.

[bigfatmonk]

Hi! I also have a RGB modded FRA N64 and I’m looking at getting an appropriate cable for when my OSSC arrives.

I’m a bit confused because when I asked if they would make a SNES cable without the sync stripper retrogamingcables suggested that a GameCube cable is needed for this console (this is also what their website says, see the note at the bottom of this page: https://www.retrogamingcables.co.uk/nintendo/n64/N64-RGB-SCART-CABLE-COMPOSITE-SYNC-CSYNC).

I have tested a gamecube cable in the past and it seemed too bright but the cheap scaler I was using didn’t work properly so I’m not 100% sure. Can anyone confirm that this console needs a SNES cable? If so, I’ll let the folks at retrogamingcables know so that they can better advise their customers in future.

[paulb_nl]

It depends on how the RGB mod is done but I believe the French N64 are mostly modded for use with the official French PAL SNES RGB cable and because you said your picture is too bright with a Gamecube cable you definitely need a PAL SNES cable.

A PAL Gamecube cable does not have the 75 Ohm resistors on the RGB lines to bring the brightness down to the correct levels.

[megari]

Yes, it is also my experience that the PAL SNES cable is the right choice for a French PAL N64 which has had its RGB circuit filled in with the correct components. For a sync stripper to really be effective against the cross hatch pattern it needs to be in the console end of the cable, not the SCART plug end. Properly shielded cables also help a lot.

Edit: French PAL N64, not SNES.

[megari]

Out of what Retro Gaming Cables has to offer, the Packapunch SNES RGB SCART cable should be fine specifications-wise, although I do not have personal experience of the Packapunch cables. They are fully shielded and have Luma sync as an option. I recommend Luma sync, if possible. Usually cables labeled as CSYNC have a sync stripper in the SCART plug end, which is suboptimal. The cable being fully shielded does help, though.

[bigfatmonk]

Thanks for the info!

Megari, I saw you recommended luma sync above but it sounds like I’d need to mod the console (flying lead from one of the chip pins along with a few components to drop the voltage?).
Is the higher risk of sync loss from the sync stripper a real concern or likely to be a negligible effect?

[megari]

@bigfatmonk, the problem I am referring to is actually not a problem with sync per se, but with high-frequency color information on the composite video line coupling into color information in the R, G and B lines, causing a visible, unwanted cross-hatch pattern. The first post of this thread has an image demonstrating the effect.

The effect happens when composite video is used for sync, the wires within the cable are not sufficiently shielded and there either is no sync stripper or it is in the SCART plug end of the cable. If a sync stripper is used, it should be in the console end of the cable to avoid the cross-hatch pattern for the simple reason that the R, G and B lines are less exposed to the electromagnetic radiation from the high-frequency composite color information.

Or at least that’s my understanding of the issue. Hopefully this was of help to you.

[megari]

Regarding the mod needed to get CSYNC out of the French N64, it is basically a single 330 or 470 ohm resistor from the S-RGB A chip pin to a multi-out pin of your choosing. In practice, this has worked for myself, but to do this properly, some sort of an amplifier for the signal may be more appropriate to avoid loading the S-RGB A pin too much and dampening the edges of the square-wave signal. S-RGB A also has a pin for Luma, BTW, so restoring Luma is also an option (I don’t know about the required components to do that properly, though).

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