The goal of this mod is to add 2 LED's that will light up the cartridge slot of the Nintendo 64 when powered on. This is mostly useful for those using clear shell cartridges. For example I primarily use a clear purple Everdrive 64, so the lights shine through nicely.

Supplies

For this mod you will need

An Nintendo 64
3D printed Nintendo 64 throat piece.
- I modified a region free throat design originally made by Greg Collins.
A soldering Iron
At least 2 LED's
Wire Strippers (recommended) or a Lighter
Breadboard wires
Heat-shrink
A resistor

Step 1: Prepare Your Wires and Components

First to get your wires ready

You will want to cut up 2 breadboard wires so that you have 2 wires with a male end and 2 wires with a female end. You may want to color code them so that you can easily identify positive and negative. Once you have all 4 breadboard wires cut, strip and tin the ends of the wires.

Now prepare another short wire about 4-6 inches long that will be used to wire the 2 LED's in series. Again, strip and tin the ends with your iron.

Now to get your LED's ready

Cut down the legs of the LED, and tin both of the leads.

I use a 3d printed solder fingers tool to hold my LED's while I prep them. The design can be downloaded here.

Step 2: Wire Up Your Resistor

We need to have a currently limiting resistor to make sure that we don't overdraw from the power supply because doing so will fry the power supply.

We need to figure out how much resistance we need to add. This LED Array calculator makes that really easy.

Our source voltage is going to be 12V.

The diode forward voltage should be around 3v but make sure to check the packaging for your LED's.
The diode forward current is the amount of current the LED can stand before getting damaged. This will vary from LED to LED. Check your packaging or data sheet to find the diode forward current. If you can not find it, 20mA is a good guess.
Number of LED's in our array is 2.

You can see for my white LED's I need a 220ohm resistor.

Once you have the resistor you need, cut it down and tin the ends.

Then solder either end of the resistor to a breadboard wire. We will be soldering this directly to the 12v, so I chose to use a red wire.

Once you are done soldering them together put some heat shrink over the resistor.

Step 3: Wire Your LED's in Series

First note which side of the LED is the anode and which is the cathode. You will want to attach the power to the anode and the ground to the cathode.

Solder one of the breadboard wires to the anode of the first LED. Next solder the bridge wire you made to the cathode of the LED. Once both of the wires are soldered on, put some heat shrink around the end of the LED so that it covers the joints completely.

Now slip a new piece of heat shrink over your bridge wire.

Next you want to slip the stripped end of your breadboard ground wire through the heat-shrink. Solder your bridge wire to the anode of the 2nd LED and solder your breadboard ground wire to the cathode of the 2nd LED. Now just shrink your heat-shrink.

Now we have our LED's wired in series!

Step 4: Assemble the New Throat

Remove the old throat piece and screw in the new one.

Now take your LED's and push them into the holes in the front of the throat. Push them in as far as they can go but make sure your heat shrink doesn't slip off and expose the solder joints.

In the picture above, the red lead will be going to the 5v, and the white lead to ground.

Once you have inserted your LED's, bend the leads at a 90 degree angle so that they will fit in the case when we close it.

Step 5: Connect Power and Ground Wires

Flip the N64 motherboard upside down and look for Pin 7 of the power switch. Pin 7 caries 12v power once the system is switched on. Solder the end of your power wire with the resistor to Pin 7. I laid my resistor down diagonally through pins 1, 2, 7 and 8.

Now on the other side of the N64, solder your ground wire to the ground plane.

Now that both power and ground have been soldered up, flip over the N64. Pull both wires through the holes in the heat sink on the top, this will put them in the right location for connecting to the LED's while also keeping the wires out of the way.