One of the cooler features of Tim Worthington’s NESRGB mod is the ability to swap color palettes on the fly. This normally requires installation of a toggle switch of some kind mounted to your NES case. It’s functional but it’s not exactly the most elegant mod. Luckily, there’s a much better solution from an electrical engineer named borti4938 that adds not only palette switching but also console reset all from the NES controller. This install guide is for Borti’s NESRGB-IGR board.
Disclaimer: This post was written for informational purposes only. I assume no liability or responsibility for damaged equipment or for any injury you may incur attempting to replicate this project.
What You’ll Need
This guide assumes you’ve already disassembled the NES and installed Tim’s NESRGB or will do so alongside Borti’s NESRGB-IGR.
Find the player 1 controller port JST connector on the NES’ motherboard. This should be the connector facing the front of the NES.
Apply some solder on the “DT”, “LT”, and “CK” pins on the connector indicated in the photo (pin 2, 3 and 4 from right to left).
Take the 28-30 gauge wire and use the measuring technique for the appropriate length.
Solder the DT, LT, and CK wires on the JST connector.
Solder the other end of signal wires to Borti’s NESRGB-IGR board. The pads are marked accordingly.
Reset Button Wiring
Locate the blue 5 pin Reset/Power button board connector on the NES motherboard.
Using the flush cutters, cut a small chunk out of pin 4. Be careful not to cut too close to the blue connector.
The idea here is you’re breaking the connection between the pin and the motherboard so the NESRGB-IGR can intercept the signal. From this point forward, I will refer to the top of pin 4 as “RI” and the bottom part of pin 4 as “RO”.
Using the 28-30 gauge wire, measure 2 wires from the blue connect to the NESRGB-IGR board’s “RO” and “RI” pads.
Now wire up the pin 4’s RI (top) and RO (bottom) to the appropriate RI/RO pads on the NESRGB-IGR.
Double Check The Install
It’s always a good idea to check your install before powering on the NES.
Check the following:
The NESRGB-IGR board is level and parallel to the NESRGB.
Make sure the NESRGB-IGR does not make contact with the bottom RF shield.
Proper Jumper is set (“HI” for front loader NES)
Voltage lines are wired to the correct locations
CK, LT, and DT are correctly wired
Pin 4 RI and RO are wired correctly
Test Your Install
With everything checked out reassemble the NES part way, since it’s a good idea to test everything before completely reassembling the NES just in case something doesn’t work as expected. That being said, reattach the 72-pin cartridge connector to the motherboard, slide the cart tray around the connector, reconnect the controller ports, reconnect the blue power/reset connector, reattach your RGB AV connection, and finally put the motherboard back in the bottom case. Make sure to insert a game cartridge, power, and controller for testing then power on your NES.
Short Reset: START + SELECT + A + B for less than 2 sec.
Flash Cart Menu: START + SELECT + A + B for longer than 2 sec.
Palette Forward: START + SELECT + D-PAD >
Palette Backward: START + SELECT + D-PAD <
NES Reset Button:
Short Reset: Short push for less than a sec.
Long Reset: Second push and hold to fully reset PIC.
Palette Switch: Press and hold to cycle through palettes.
The NES powers on but the palettes keep switching You most likely have your “RO” and “RI” wires mixed up.
The NES no longer powers on – Check to make sure the Jumper is set properly. – Check pin 4 is wired correctly and separated from one another.
In game reset doesn’t work This can also be a mismatch of “RI” and “RO” wires but you’d see see the palette cycling too. Check the controller “CK, “LT”, “DT” wiring and ensure they’re going to the correct NESRGB-IGR board pads.