Hey guys,

Just got a power supply board for my pedals (9v dc outputs) and was wondering, when the pedals are plugged in to the power supply, do the batteries still drain?

Like, can I leave the battery in there, connected, as a backup just incase the power supply fails? Or will it drain out over time?

Jacks will be plugged into input jacks at all times.

"Sit your ass down in that f@%$ing chair and drink your GODAMN TEA!!" - Cid, FFVII

Gibson Les Paul Standard (trans amber, 60s neck)
USA Fender Strat
Westfield acoustic
Washburn 12-string acoustic
Encore bass
Aria acoustic bass
yeah, they'll automatically stop draining the batteries (at least, usually) although I wouldn't let the batteries in cause when you turn the power supply off, the effects will probably automatically use the batteries again
A hero of war, Yeah that's what I'll be

you should definately keep the batteries in. they will die eventually from age but they wont lose power as if they were being used. if the pedals are connected to the power supply it automatically overrides the battery power.
I've had a battery in my Bad Monkey for months and it is connected to AC power constantly. I just unplugged it to check and it works (ie battery is still fine).

I've also heard but never experienced myself that pedals get funky or add lots of noise if battery dies and your using AC power.