The other day I was very excited to discover an illuminated switch at Radioshack that was roughly the correct size, shape and action as a standard guitar pedal push-button switch. This is great for pedals because the indicator of whether or not the guitar effect is on would be built directly into the switch, eliminating the necessity of excess drilling and wiring.
True, the model switch that I bough is an SPST switch, which is a less-than-ideal replacement for the usual DPDT bypass switch. Nonetheless, I figured that I could make it work as a guitar bypass switch by having it control a simple DPDT relay.
I was about to wire it all up into my newest guitar pedal when I realized that this switch actually required 120 VAC to illuminate! What's up with that? This bugged me a great deal as I would be working with low-voltage DC, not high-voltage AC. This was not going to do.
I immediately resolved to replace the little bulb inside with an LED. This required a near total dissection of switch, but after a little figuring out, I am happy to report that the mission has been accomplished. Follows is a method for converting an illuminated Radioshack switch from 120VAC to 3-12 VDC.
Step 1: Go Get Stuff
You will need:
An illuminated Radioshack switch (#275-671)
A 100 ohm resistor
A zip tie
A soldering iron setup
A flat head screwdriver
Step 2: Take It Apart
Use your screwdriver to bend back the metal tabs on the bottom that are holding the unit together. Carefully remove the black plastic mechanism from the bottom such that it is left in one piece (the springs and levers shouldn't fall out of it).
Next pull out the white non-conductive plate, the hollow cylinder, spring and plunger.
Remove the clear cap from the top.
Step 3: Clip the Bulb
Use wire cutters and clip the bulb away from the top of the cylinder, leaving as much wire as possible still attached to the switch.
Step 4: Add a Resistor
Remove their 330K ohm resistor and replace it with a 100 ohm resistor.
Step 5: Wire the LED
Wire the LED in place where the mini light bulb used to be.
Step 6: Put It Back Together
Carefully reassemble it. It should be more or less like the way you found it.
Press the metal tabs back in place with your pliers.
If it is still a little loose, wrap a zip tie tightly around the bottom of the casing.