What would make a pedal quickly drain 9V battery?

[Dito]

Hey gang,

I built an overdrive pedal for a friend. He's only used it for about 4 or 5 practice sessions, and the 9V battery is already dead. It was built with the "no input plug = broken ground" design, which works. The LED goes dark, anyway.

The only wrinkle in his setup is that he's playing a bass with active pickups. I don't know anything about active pickups, but my basic understanding of circuits in general is that it shouldn't matter.

Any guesses?

[aron]

Something is drawing too much power. Did you check out how current the pedal is using? Set the meter to mA and put the meter in series with the battery. If it's not drawing too much power, then somehow the pedal is not being turned off even though the plug is unplugged. While the meter is in series with the battery, unplug the cord and see if it is still drawing power.

[Cozybuilder]

If you post a photo we might be able to see something amiss.

[Dito]

I'll have to get it back from my buddy to diagnose anything. He's fine with an adapter, but I still want to know.