SNES-Mini RGB Measurements

I tend to do the opposite and leave it alone. Here in the states RGB is still something considering the exception and not the norm and you never know if a console is going to be given away, stolen, or whatever and as soon as they find composite doesn't work into the garbage bin it goes. I would like to think if someone is paying me to do a RGB mod for them they're going to make sure to note it as such when selling it but you never know.

Plus I can't take a composite cut SNES/N64 to a friend's place without bringing my gear with me. I'd rather not lug around a 30lb PVM just to play Mario Kart.

 

Yes I was planning to cut composite video and use that pin for C.sync. I will never use anything but RGB, so it's not an issue for me Adding a LM1881 is not a problem, but since the RGB encoder already has C.sync it might be better to use that instead.

As said, it does work if I solder a wire from the RGB encoder to the cut pin on the AV-out. But I suspect this isn't the correct way to do things.

Luminance from S-video might not work for me, as I'm running everything through my Extron RGBHV matrix, and it doesn't like c.video, but works fine with c.sync. I don't know if Luminance would work though.

 

US consoles have a pin spare for Csync, pal ones do not.

He said someone with experience with pal consoles to chip in, so I did. NTSC consoles are different.

 

Where is the 12V coming from? Is there an extra regulator on a PAL board? Maybe you can add a switch in that would switch the output of pin 3 from 12V to CSYNC so at least then it could be used with a regular SCART TV as well.

Or just take the regulator out, then at least it can be brought back to stock if needed.

 

I don't mind changing the c.video pin to c.sync Just wondering if the signal needs any external components between the c.sync line on the RGB encoder and the AV-out port.

In this schematic from the older SNES models you can see that there are components between c.sync (pin 8) and the AV-out:


But since my SNES is a newer 1CHIP-02 and it uses an S-RGB A encoder, which for starters has c.sync on pin 7, this schematic can't be used. I guess I could try connecting the Luminance signal to the cut c.video pin, at least that's wired up correctly on the EU SNES. I'm just not sure if it will work as sync through the Extron matrix switch. It would be easier to do it right the first time around

Edit: I did some more searching and now came across this thread almost immediately:
http://nfggames.com/forum2/index.php?topic=3083.0

I think this is exactly what I'm looking for:


Although I'm not sure what value C50 is, and which transistor I should use. Also, I'm pretty sure there's an error because according to this schematic both c.sync and chroma connects to pin 8 on the AV-out port. Surely that should have been pin 3 for the c.sync, but that's of no concern of mine, since I'll be attaching it to pin 9 (c.video)

 

Here's a link to the latest version of that circuit.

http://www.assemblergames.com/forum...-CPU-RGB-02-Video-circuit-(w-S-RGB-A-encoder)

The transistor is a 2SC2412K or if you want through hole then a 2SC1740S. I'm not sure about the value of C50 though but it is marked as C46 330pf on another schematic with the same C-Sync circuit.

https://dl.dropboxusercontent.com/u/36237540/SNES/jwdonal/schematics/snes_schematic.zip

 

That circuit is not for the 1-Chip. The first diagram you posted is for the original system.

Use pin 18 on the S-RGB A for CSYNC. It is buffered. No extra circuitry needed.

 

Thanks a lot On the improved schematic you linked to, the capacitor is a 47pF, so I might try that

I know, but I figured that it might be wired up the same way regardless. I didn't know it had a C.sync output, so maybe I'll just try that, if you're sure no extra components are needed.

 

I've tried using Csync on Pin 18 for my PAL SNES 1Chip 02 (S-RGB A) and it generally works with my cheap upscaler but
the voltage is really high (I forgot the exact values but it was about 8V at least) and my scaler looses sync in interlaced display modes.
A voltage divider resistor for ~5V output made the auto sync detection on my scaler work better but it still looses sync in some display modes that way.
Any idea what could be wrong?

 

He measured csync in this thread and it was 5v.

Odd that yours is coming in higher...

 

Well, maybe I'm measuring it wrong? I just have a common multi meter and I'm looking at DC and AC at pin18 to GND.

 

Multimeters are no good at measuring signals, just power.

 

I tried using Luminance as sync, but as I expected the Extron matrix didn't like this. After reading Horstenss post above, I just wired pin 7 to the AV-out. This works fine and there's no interference at all I might try building the small circuit in the schematics another time, just for a more correct sync. I don't expect it will make any improvements to the video quality.

 

I actually went with pin 7 as well here. My only fear is that it's a direct connection to S-CPUN and it might fry the chip some day ><

 

^ so, is there a way to do it better? maybe through a diode or something?

 

If S-RGB pin 18 is a buffered TV-level CSYNC output, the correct way to wire it is through a 75 ohm resistor and 220 uF (or larger) cap, just like composite/luma. You definitely shouldn't directly connect it, or leave out the capacitor, because the TV's load could draw excessive current.

Or you could rebuild the discrete transistor sync driver in the schematic above.

 

you mean the parts I highlighted in green?



can't say I get that completely... pin18 in NC , is that supposed to be a c-sync output?

 

Pin 18 isnt NC, the person who drew that schematic was wrong at the time.

Check his updated version (which was posted in this thread too).

http://www.assemblergames.com/forum...-CPU-RGB-02-Video-circuit-(w-S-RGB-A-encoder)

 

^ so it's pin18->75ohm->220mf = c-sync out ?

 

Luma goes cap then resistor.

Video termination isnt my strong point, better wait for calpis to chime back in.