Oooh, look at the pretty :)
Yeah, I was bored.
First, we’re going to start with a molex connector (4-pin PSU power connector). For this example, I’ve used a molex-to-two-floppies adaptor cable I had laying around, with a female molex socket on it.
First, we depin it.
Identify the second pin in from the end with the red wire. This should be the pin with a black wire, the one next to the red wire.
With this hole identified clearly, drill a hole through the plug, through the existing hole, so the existing hole is enlarged, of about 3 mm or 3.5 mm diameter.
Take a 3 mm LED (whatever kind you like) and cut the anode lead off so it’s really short, about 2-3 mm, and take the resistor, of appropriate resistance to suit the LED, and cut it off short on one side too, 2-3 mm long. Solder the resistor to the LED, so that it’s really close together.
Bend the leads and trim them off as shown, and solder as shown. Pretty self explanatory.
You should then be able to reassemble the plug as shown, and put the LED in the hole. You can’t let the LED protrude into the plug too far, or else the plug can’t be plugged in.
Just remove that second black wire completely, leave it out, it’s not really needed.
(I used a surplus LED that I had laying around which had both leads already cut short, so I needed to solder the cutoff resistor lead back onto the cathode of the LED, however, with a new LED, you won’t need to do this.)
(Messy floor is messy, yes, yes, I know)
Here’s the finished result with a red LED.
The translucent white plastic does an effective job of diffusing and spreading out the light.
Here’s another one with a blue LED.
This would be nice with one of those triple-die integrated-IC colour changing LEDs, but I don’t think you can get them in the T1 3 mm package, only 5 mm.