The Nintendo Wii ships with a composite video cable that is capable of 480i resolution. Currently first party component cables, which allow for 480p resolution, are available through retailers and directly from Nintendo. However, when attaching the component cables, one loses the ability to output composite video. Why is this an issue? Well, it may be that you take your Wii over to friends houses frequently and would like to only have to take a single cable. Or, you may be like me, and use an LCD computer monitor for your Wii's display. My monitor has composite but no component in. To support high definition signals, I use a small transcoder box, the Mayflash YPbPr to RGB transcoder, that only supports progressive scan modes. However, many older games, such as GameCube games, and even some of the new Wii games, like Rayman Raving Rabbids, don't support progressive scan. In these cases I end up with a black screen and need to switch cables to play the game. What a pain.
Luckily, this cable does both component and composite output -- and it's selectable at the flick of a switch. We'll take a standard first party component cable, and a few bucks worth of parts from Radio Shack and put together a cable that is selectable between composite and component output
Step 1: Gather Required Parts
For this instructable, you'll need the following items:
Wii Component Cable
A small amount of wire
SPST Switch (about $2.00 for 2 at Radio Shack)
Phono RCA Jacks (about $2.00 for 4 at Radio Shack)
Composite video cable
Hot Glue (not pictured)
Butter Knife (not pictured)
Paperclip (not pictured)
Step 2: Crack Open Component Cable
Fortunately for you, the Wii AV cables are pretty easy to crack open. Take your handy butter knife and slide it into the little holes pictured. Gently press and angle the knife to pop back the cable housing to provide access to all of the wires.
Step 3: Locate and Cut Mode Wires
Now, you'll want to locate and cut the mode wire. You need to do this because you'll add in the switch in the middle of this circuit. If you leave this connection shorted all of the time, then the Wii will automatically output over the component connections. Adding in the switch allows you output over composite.
You'll notice that there is a very short span of wire here. Take your wire cutters and cut this open. You'll want to then strip the wires and solder some connectors to a longer wire. If you look at the plug from the right angle at this point, it will look like it has rabbit ears sticking up. I've found that positioning the plug and wires like this makes it easiest to accomplish the next step.
Step 4: Add in Composite Video Pin
Unfortunately, the Wii component cable does not have extra pin headers included in it, so you'll need to find something else to use for a pin. In my case, I used a paper clip that I trimmed slightly and then hot glued into place. For the location of the pin, you'll be placing the new pin between the white wire and a black wire that is nearest the white wire.
This is the most difficult part, so take your time on this. It may be helpful to put a small kink on the end of the paperclip to help it make contact when inserted into the Wii. Also, this picture shows the paperclip hot glued in place before the yellow lead wire was soldered on. You'll want to do the soldering than hot glue, otherwise you'll find that you've just melted all of your hot glue and made a mess.
Next, you'll want to connect the ground for the composite video. In theory it won't need this if you already have audio going to the same device, but it never hurts to have more grounds. All of the big thick black wires are ground, as is all of the little pieces of metal that are sticking up out of the cable. In my case, I just jammed by ground into the cable and secured it place with some hot glue.
You'll probably want to test it at this point. The positioning of the pin is very tricky. You can test it by connecting the lead from the new pin to the center of a composite cable, and the ground to the shielding of a composite cable.
Step 5: Slide Casing Back on and Connect Switch and Phono Jack
The next step is to reassemble your cable. I found that by feeding all of my wires out of the "bottom" of the cable (the side that has a "don't throw in trash symbol"), I was able to get everything out and everything else put nicely together. You'll want to use a fair amount of electrical tape in this process to ensure that all your connections are protected and to help keep the wires together as you bring the casing back down over the plug.
The next step is to solder in the switch and phono jack. Unfortunately, I didn't take pictures of this process. On my cable, the switch is soldered between the two black wires. Since you've got a SPST switch, it doesn't matter which connection gets soldered where. With regards to video, the yellow is the composite video signal and the blue is the ground. I soldered the yellow to the center terminal of the phono jack, and the blue to the ground terminal. It can't hurt to give it another test at this point before you tape everything back together.
Step 6: Tape Up, Connect, and Enjoy
Now you're nearly done. The final step is to tape everything into place. I just used gobs of electrical tape there. You'll want to make sure that neither of your connections are to the right of the plug (looking down at the game cube ports with the Wii facing you), because they'll get in the way of the power.
If all has gone well, you should now have a cable that is selectable between composite and component output. While there was some talk on the Wii message boards about the composite always being enabled if the machine was in 480i, I've found this not to be the case. So, you'll still need to get up and flip the switch and reboot the Wii to switch to 480i, but at least you're not having to muddle with cables going in and out of your Wii.