Using parts from an old power supply and a case fan, I've built a Molex Y-splitter. I've seen these retail for around $4 (more if you take shipping into consideration). The parts I used were leftovers - total cost of $0.00.
Step 1: Materials & Tools
- Leftover (male) power plugs from old power supply
- Female molex plug (mine was from a case fan)
- heatshrink (or electrical tape, if you don't have it)
- Thin-nosed plyers
- Wire stripper
- Incredibly tiny flathead screwdriver (like the kind you find in a eyeglasses repair kit)
- Soldering iron and solder
Step 2: Remove the Pins
Step 3: Remove the Pins from the Wires
Step 4: Reattach the Pins for the Male Plug
By now you should have a set of four wires that have no plug attached. Use the wirestrippers to remove about a centimeter of sheath from each wire on one end of the bundle. Now take the pins from the male plug and bend the clamps 90 degrees like in the picture. Use the flathead to push the locking tabs back out of the pin. Then bend the clamps to hold the wire on and solder the wire to the pin. This is much easier if you have one of those soldering "helping hands" stations (believe me).
When you've got all four pins reattached, you might want to put some heatshrink on. Or not - depends on what you want. Put them back in the male plug, making sure they are arranged in the same pinout as the other untouched male plug you have.
Step 5: Attach the Female Plug
Strip about 7mm of wire from the untouched ends of the wires left. Twist together the like colors (make sure you have the black wires paired up correctly!) and attach them to the pins just like you did with the male plugs. You can tin the twisted pairs if you want (and if you know how to do it right, unlike me) if that makes it easier for you. It didn't help me.
You will probably want to put some heatshrink over the pins where they connect with the wires. I put my pins back into the plug and had metal sticking out, so that's why I did it.
The easiest way to make sure you have the pinout right is to plug the empty female plug into one of the male plugs and line up the wires that way. Again, make sure you have the black wires lined up correctly. When you push the pins in, make sure the tabs clicked out to lock the pin in the hole.