SNES PAL RGB voltage levels

[Elwood89]

Hello!
I decided to upgrade my cheap chinese SCART RGB cable (fuzzy, lots of audio humming) with a better cable, one that has separate shielding over the audio lines.

The chinese cable does have all the usual resistors, 75 ohm on R, G, B and Luma (was originally composite, I soldered it to Luma for sync), and 180 ohm on 5v -> scart 16.

What i noticed during testing, is that while the voltage on Luma is close to spec (around 0,8 v), R, G and B output ~1,15 v. The measurements were made with the console running, connected to my Samsung LCD TV. I also have a spare SNES mainboard and it gives the same results. The Samsung does have the expected impendance of 75 ohm on the RGB lines - checked with the console cable detached.

So the RGB levels are above the SCART spec which says 0,7 v peak signal (some people say 1v, I'm not sure). My question is - should I be worried about that and replace the 75 in the SNES Scart head with something stronger, or just leave it as it is now?

[kendrick]

Hi Elwood, welcome to GamesX. To answer your question, I think that the voltage is fine on the cable. You said that it was a higher-quality cable and connector overall? I would bet that the media in each individual signal wire is higher spec and therefore lower resistance, which is why you're seeing a slightly higher voltage reading.

To be clear, 1.2 volts (over a stated .7 or 1.0 volt spec) is not significant in this application. If you were looking at an order of magnitude higher (like 2 volts or 5 volts) then that would be a problem that could cause damage over the long term. But what you're looking at here is most likely nothing to worry about.

[Elwood89]

Hello! I did not write it clear enough, the measurements were taken with the cheap cable. My idea was to desolder the end connectors (snes and scart) and use them with the new hq cable, which I haven't done yet.
Yesterday evening I found this http://retrorgb.com/snes1chip.html , gotta check if my mainboards are of the 1-chip kind. The resistors they are suggesting for this mod are 750 ohm, seems pretty high, I thought they made a mistake and meant 75 ohm, but the color codes on the photo confirm 750.

[kendrick]

Thanks for clarifying. Everything we know about SNES video output from the last 25 years is pretty well summed up here:

http://gamesx.com/wiki/doku.php?id=av:nintendomultiav

I believe that the 750 ohm number you cite from that source is an error. Everything I've ever read suggests that PAL SNES cabling always uses a 75 ohm resistor on each line. However, since I'm American I've only ever had direct experience with the capacitors on NTSC cables, so I'm open to being corrected if someone else knows differently.