Clean RGB Install (SNES)
The SNES already outputs RGB out of the AV port, however it has a DC offset which makes it incorrect voltage levels to most monitors.
Most people solve this with making custom RGB cables with AC coupling capacitors and resistors. This is ok, but it's far from perfect. It introduces all problems that AC capacitors add (field droop, tilt, common mode noise coupling from the receiver side and more.
All the RGB mods I personally make are called the CleanRGB. It aims at correctly fixing the console itself to output IRE correct voltage level and signals, and the cable is then a pure DC cable with direct connections, no hidden capacitors, sync strippers, resistor or other magic.
The benefits of this are pure, perfect RGB signals not affected by your cable, receiver, or noise.
This install will involve:
- Getting RGB and Sync inputs from S-RGB or PPU2 to CleanRGB
- Severing traces from stock RGB and Sync outputs to AV Port
- Wiring RGB and Sync outputs from CleanRGB back to AV Port
- Tuning the CleanRGB for perfect IRE levels
Start by installing a CleanRGB Universal board into the SNES. Tap the RGB and Sync inputs directly from the S-RGB (BA6596) chip or PPU2 or specific transistors that connect to the PPU2.
Here is where I chose to install it for the SNS-CPU-GPM-02 variant.
- R bottom left Q3
- G bottom left Q5
- B bottom left Q7
- CSYNC via to left of Q3 the bottom of 3 vias in a row, after the 2 vias one on top of the other
- 5V is pin 27 of cartridge connector
- Grounds are eon capacitor C84 and C98
- Outputs to AV port pins (AV port traces cut)
The CleanRGB works on every version of SNES, including the Jr models. Every SNES has the S-RGB chip or PPU2 chip.
The R, G and B In go to the CleanRGB inputs, and we tap 5V from any 5V point such as the AV port or regulator, and ground from the nearby ground.
Here the RGB and Sync Inputs are coming from the S-RGB on the other side of the board and passed through an open unused capacitor hole.
The RGB and Sync outputs are connecting to the AV Port.
On this model (SNES Jr) shown, there are no connections to the AV Port for RGB so nothing needs to be cut or severed.
Next, we need to disconnect the AV port from the existing connection to any RGB pins.
The simplest way is to expose the traces running from the AV port pins and cut them. Each revision board is different layout so gently scrape away the solder resistor to reveal the copper traces coming off the AV port pins and cut the R, G, B and Sync pins.
For example, here are the cuts on a SNS-CPU-GPM-02 variant.
NOTE: There is a ground copper plane on the top layer as you can see near the red trace that's cut to the right of it is a bit of exposed ground (just above the letter R).
This isn't a problem just try not to hack away at the traces and merge the traces into the ground plane. Cut as close to the AV pins as physically possible.
īģŋ
Once done it's a good idea to cover the exposed copper with conformal coating/nail varnish to seal them.
Now wire up the RGB and Sync outputs to the AV port pins.
Checkout the setup guide for tuning the CleanRGB, or for quickness set your dials to the following positions and then tune by eye.
Using our CleanRGB SCART cable, here are the results on a SNES.
TODO
