A modding board to bypass the SNES' video encoder by using TI's THS7374 video amplifier, to achieve optimised RGB video.
This modification works with all 1-Chip models (PAL/NTSC).
⁓ Designed with ♥ in Germany ⁓
You can order the PCB directly from OSHPark.
Of course, feel free to use the gerber files with any manufacturer of your choice.
Use 0.8mm board thickness to ensure an easy and clean installation.
Make sure that your console is a 1-Chip model. If your console is a SNES2/Mini/Jr., this is the case by default.
Otherwise, this can easily done by looking for an indicator at the main board:
1-CHIP-01/02 models
- disconnect +12V from MultiOut Pin 3: remove R28
- disconnect stock RGB: remove R15, R16, R17
- remove decoupling caps from MultiOut (optional¹): remove C44, C45, C46, C47
- isolate the bottom side of the modding board to avoid any shorts
- solder the modding board onto the pins of the MultiOut
- solder a wire from the via next to R6 (SNES main board) to pad 'R' (modding board)
- solder a wire from the via next to R7 (SNES main board) to pad 'G' (modding board)
- solder a wire from the via next to R8 (SNES main board) to pad 'B' (modding board)
- solder a wire from the via that is nearest the bottom left corner of designator C6 (SNES main board) to pad 'CS' (modding board)
1-CHIP-01/02 models
These models already have C-Sync connected to pin 3 of the MultiOut.
You can either use this (not recommended) or:
- disconnect C-Sync from MultiOut Pin 3: remove R12 (optionally remove R9, R10, R11, Q1 as well)
- disconnect stock RGB: remove R15, R16, R17
- remove decoupling caps from MultiOut (optional¹): remove C44, C45, C46, C47
1-CHIP-03 model
This model hasn't C-Sync connected at all, so you'll have nothing to do here.
- disconnect stock RGB: remove R15, R16, R17
- remove decoupling caps from MultiOut (optional¹'²): remove C44, C45, C47
- isolate the bottom side of the modding board to avoid any shorts
- solder the modding board onto the pins of the MultiOut
- solder a wire from the via next to R6 (SNES main board) to pad 'R' (modding board)
- solder a wire from the via next to R7 (SNES main board) to pad 'G' (modding board)
- solder a wire from the via next to R8 (SNES main board) to pad 'B' (modding board)
- solder a wire from the via under the left pad of R9 (SNES main board) to pad 'CS' (modding board)
SNN-CPU-01 model
Since this model doesn't have stock RGB, here is no preparation needed.
- isolate the bottom side of the modding board to avoid any shorts
- solder the modding board onto the pins of the MultiOut
- solder wires from the vias (shown in the install diagram below) to the appropriate pads on the modding board
¹ if you remove the decoupling caps at the MultiOut, make sure to occupy C22, C32, C42 & C51 on the modding board! Never use both at the same time!
² if you leave the decoupling caps at the MultiOut, make sure to occupy at least C51 on the modding board! (1-CHIP-03 only!)
Double-check continuity between connections:
- 'R' (modding board) ⇄ S-CPUN pin 156 / S-RGB pin 5 (SNES main board)
- 'G' (modding board) ⇄ S-CPUN pin 157 / S-RGB pin 3 (SNES main board)
- 'B' (modding board) ⇄ S-CPUN pin 158 / S-RGB pin 1 (SNES main board)
- 'CS' (modding board) ⇄ S-CPUN pin 151 / S-RGB pin 7 (SNES main board)
The THS7374 has a low pass filter on each of the four channels which can be turned on by shorting jumper 'J:LPF' on the modding board. This is mostly needed if you wire the console directly to a flat-screen TV. There's no need for the low pass filter on analogue devices.
If you use an OSSC or a Framemeister, it's better to use their filter options.
In order to get rid of the ghosting issue (which 1-Chip models are known for), simply replace C11 (SNES main board) by a 470nF ceramic capacitor (0805 for normal/fat models, 0603 for SNES2/Mini/Jr.).
You will need a RGB cable with 220µF electrolytic capacitors on each of the 'R', 'G' & 'B' lines. The positive end is facing towards the console.
This modding board is designed to output TTL level C-Sync directly at the MultiOut of the console.
With that in mind, make sure you're using a suitable cable with a 470Ω resistor on the sync line to use it with most consumer products (like TV's, OSSC, Framemeister)!
I am not responsible for any damage to you, your devices or anything else!
If you do the modification, you do it at your own risk and responsibility!
Most of the credits should go to borti4938. He has made the actual (slightly different) circuit and inspired me to design this board. Thanks man! Thanks to Voultar for research and findig the ghosting fix! Thanks Bob, for your awesome and informative website RetroRGB!
And of course, thanks to the whole retro gaming community for keeping the spirit alive!