help with SNES Jr. RGB mod

Started by VincentPrice, May 05, 2013, 08:58:41 PM

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Hi there,

I came to this forum through a helpful guide on how to mod a SNES Jr to send out an RGB signal. I bought thin wire, 75 ohm resistors, opened up the console ready to go...only to find out the chip and motherboard are different from the guide.
Would the pins to attach the wires to be the same? If not, how would I find out where they go without breaking my SNES (not sure how likely this is, I know very little about these things).

Here's a close up of the chip. I'll attach a picture of the board's serial in the next post.

Welp, it's not letting me post a close up of the board despite the file being small enough.  Board's serial number is SNN-CPU-01.


That's the same chip shown in the guide, here's the pins that you need for RGB and S-video:

Pin 7: Sync
Pin 12: Chroma
Pin 17: Luma
Pin 20: Red
Pin 22: Green
Pin 24: BLue


Ok, i got confused since the serial number was different. I just follow the guide and not have to wire chroma and luma (since I don't need to mod it for s-video).


Correct, you do not have to wire chroma or luma.


Woooooww holy thread necromancy. I did a search on this problem and found my own ancient thread!

Anyway, the mod at the time was successful. I didn't bother with the composite sync wire because I couldn't get the wire in place and I'm using RGB only anyway.
The issue I'm having (and I'm not sure if that's always been the case or just popped up) is a buzzing noise. This is especially noticeable during parts of games with no music. My PS1 had the same issue, so after a lot of testing eliminating the amp, the tv, speakers etc I opened up the PS1 scart and found a loose wire. After (sloppily) soldering that in place the buzzing was gone. A grounding issue then.

The SNES scart doesn't have any loose wires. This is a PAL scart. I used it with my previous PAL SNES and that worked, and my tv recognizes this as an RGB signal with my SNES JR. When I first got that PAL SNES I ordered a regular scart cable which blew up right away. From what I read though you need a Gamecube/N64/Wii scart cable for an NTSC SNES. Strange, because this one does work for hours on end. The only thign is that during startup the picture seems excessively green but that corrects itself after a few seconds, as if it has to warm up.
This is definitely a PAL SNES cable though, it's been modified by the seller as it has the resistor soldered in.

I ordered a Gamecube scart to see if that solves the buzzing noise and the green at start up. Does anybody here have their 2 cents on this?


Hm, been doing a bit more searching. I used the guide on RetroRGB at the time. He's changed his guide to now use an RGB amplifier circuit:

but still has the old guide up:

Except this one no longer includes attaching the sync wire and recommends using a specific cable. It also now says to use 100ohm resistors instead of 75ohms.

Now I'm just confused.