I found a couple of beat up GameCube controllers at a yard sale. One 1st party and the other is 3rd party. Both have bad thumb pads on the main joystick, but I snapped them up for parts so I didn't care. It feels wrong to cannibalize the 1st party controller when I have a perfectly inferior 3rd party controller to dismantle, so I'll be using the D-pad of the latter. Unlike my previous mod, this mod will be permanent due to the fact that the D-pad will need to be glued in place.
Step 1: What You'll Need
1 - 3rd party GameCube controller (preferably broken). You can use a 1st party GameCube controller, but you'll need a tri-wing screwdriver to take it apart.
1 - Small Phillips screwdriver
1 - Hand drill or rotary tool (like a Dremel)
1 - Grinding bit for the drill/rotary tool
1 - Piece of course sand paper
1 - Pair of safety glasses to wear when grinding
1 - Tube of epoxy for bonding plastics
1 - Toothpick for mixing and applying epoxy
1 - Metal bottle cap for mixing the epoxy in
Step 2: Begin Tearing Down the GameCube Controller
*If using a 1st party GameCube controller, you'll need a tri-wing screwdriver that you can find on EBay. I included a picture of mine.
Remove the back of the GameCube controller and put it to the side.
Step 3: Removing the Circuit Board From the GameCube Controller
Step 4: Removing the D-pad From the GameCube Controller
Step 5: Begin Tearing Down the NES MAX
Step 6: Removing the Circuit Board of the NES MAX
Step 7: Removing the Cycloid
Step 8: Taking the Cycloid Apart
Step 9: Grinding and Sanding the Back of the GameCube D-pad
Put on some safety glasses and grab the hand drill/rotary tool. Then grind off the fulcrum on the back of the D-pad using the grinding bit. There are four support members that will also need to be ground down. I did my best to remove most of the support members and the center post and then switched to sandpaper for the outer ring. Don't sand off too much though, the idea is to sand off just enough so that the cycloid will snap together around the D-pad. Rinse off any residual plastic powder and allow the D-pad to dry.
Step 10: Glue the D-pad to the Cycloid
Step 11: Put It Back Together
Step 12: Troubleshooting
I'm not sure if every NES MAX has this problem, but I've always had trouble getting a response when pressing the Up direction and the Down direction (even before modding). I've had to press harder than the Left and Right directions in order to elicit a response from the controller. Thinking that something might be wrong electrically with the conductors, I removed the controller casing and played a little Fester's Quest using the rubberized conductive resin and circuit board alone. The portly Addams family member responded immediately upon pressing all four directions, indicating that there was nothing wrong with the conductors. This meant that there was a mechanical problem having to do with the throw distance of the Up and Down directions.
The only way to correct this problem is to beef up the cycloid where it rests on top of the Up and Down conductors. To prove this theory, I put a piece of cardboard from a 12 pack of Sprite across the Up and Down points of the cycloid and it worked. So in my case, I just needed to apply a dab of epoxy, equal thickness to Sprite cardboard, on both points ;) The nice thing about this epoxy is that it doesn't shrink and it can be sanded if applied too thick. Let cure for 24 hours before putting back into the controller.