Neo Geo RGB and Sync Voltage levels

[TobyRieper]

Hey guys, just finished off my CMVS using and MV2F - works great, fantastic sound, nice vibrant RGB image etc. I understand my RGB voltages should be approx 0.7v p -p, Is that correct? As for the Sync line does the voltage need to be around 1v (using SCART retrotink).
Do I need a capacitor on the sync line? I currently use a 220uf all because it was in a SCART cable I had made by retroshack for the NeoCD.

I have a digital scope to check the levels. Thanks!

 

[ShootTheCore]

Your target should be around 660mV for the RGB lines, and sync should be between 250mV and 900mV for SCART.

As for a capacitor in the sync line, it's considered "proper" design to have the cap on the console side so that the cables are just straight runs. Some of the console manufacturers (like Sega) left the caps off their RGB sync to save a few cents, which is why cables for those kinds of consoles have a cap in the SCART head.

You may find this article helpful: https://www.retrorgb.com/osscarcadetimings.html

 

[TobyRieper]

Your target should be around 660mV for the RGB lines, and sync should be between 250mV and 900mV for SCART.

As for a capacitor in the sync line, it's considered "proper" design to have the cap on the console side so that the cables are just straight runs. Some of the console manufacturers (like Sega) left the caps off their RGB sync to save a few cents, which is why cables for those kinds of consoles have a cap in the SCART head.

You may find this article helpful: https://www.retrorgb.com/osscarcadetimings.html

So I'm just a little out on the RGB lines? I guess that just affects the brightness. I needed 110/120 ohm resistors but only had 100ohm. Thank you for the link to the article. I don't think it would make any practical difference at all to put the cap on the console side? Cheers

 

[ShootTheCore]

I don't think it would make any practical difference at all to put the cap on the console side? Cheers

Well, as I said the "proper" way to do it is to put the cap in the console, not the SCART head. If the cap is at the console then the signal going out to the cable is already the correct voltage and is less prone to signal cross-coupling interference from the other lines due to improper shielding in the cable.

 

[TobyRieper]

Well, as I said the "proper" way to do it is to put the cap in the console, not the SCART head. If the cap is at the console then the signal going out to the cable is already the correct voltage and is less prone to signal cross-coupling interference from the other lines due to improper shielding in the cable.

Oh, right. I understand Thanks so much. I'll install the cap, console side. Thanks

 

[awbacon1]

Your target should be around 660mV for the RGB lines, and sync should be between 250mV and 900mV for SCART.

As for a capacitor in the sync line, it's considered "proper" design to have the cap on the console side so that the cables are just straight runs. Some of the console manufacturers (like Sega) left the caps off their RGB sync to save a few cents, which is why cables for those kinds of consoles have a cap in the SCART head.

You may find this article helpful: https://www.retrorgb.com/osscarcadetimings.html

oh all the low down dirty ways to save a buck Sega

 

[hatmoose]

As for a capacitor in the sync line, it's considered "proper" design to have the cap on the console side so that the cables are just straight runs. Some of the console manufacturers (like Sega) left the caps off their RGB sync to save a few cents, which is why cables for those kinds of consoles have a cap in the SCART head.

As far as i'm aware the Sega Saturn and the Neo-Geo AES are the only consoles that attenuate their RGBS signals properly in the console - pretty much everything else relies on caps and resistors in the SCART shell to tame down those TTL voltages.

So Sega got it right (one time and one time only time) with the Saturn - but even then there is a sting in the tail.
The USA/JPN Saturn sends lovely, clean 75 Ohm CSYNC out on pin 1.
The PAL Saturn sends 9 volts out on pin 1 for SCART signaling