I have 3 LED's under both of the pickups, and I wired it to the pot cavity. There, I it all hooked up to one of those 9-volt battery holders (like the ones that hook up to 9-volts in a smoke alarm)

Every 9 volt I use dies really quickly. Does that mean I should put a resister on or something?

no, it sounds like the battery doesnt turn off, which might be why it dies so fast. a resister would just make the led's dimmer, since a resistor resists the flow of electricity.
The Gear:

Custom Strat
Mesa Boogie Stiletto Ace
Fulltone OCD
Electro Harmonix Small Clone Chorus
Dunlop Crybaby Classic
MXR EVH-117 Flanger
Fulltone Soul Bender
Its hooked up to a switch though. I guess I should have added that
yeah, you could use a resistor. It should constrict the amount of current going through the circuit, which would extend your battery life.

Since v/r = i. Any 9v battery will have a lifespan of a certain mAh (miliamp * hours). The lower the current draw, the longer the battery life. Lookup the specs for your LEDs, they act like diodes, so they should have some sort of operating voltage and operating current.

The way it works would be [9v - (operating voltage, typically around 2~3volts)]/operating current (typically around 10-20mA). That'll give you the resistor value you optimally want, round to the nearest commercially available value. Make sure you get a resistor that can handle the power (1/2w resistors should be fine, but if you're feeling paranoid, 1w resistors will be able to take pretty much any/every led).

This formula changes depending on whether the LED's are wired in series or parallel. It should also dim your LED. If you really wanted, you could probably mount a trimpot instead of a resistor in your control cavity to adjust the brightness of your LED's.
Last edited by greenbox at Jul 5, 2006,