I was just given a broken boss OS-2 by a friend. After testing it out earlier I find that it works with a 9v battery when an adapter is not plugged in. However when I plug in an adapter, the pedal won't turn on and no sound comes through the amp. I think I am using the right adapter, a 9v DC, and I tried multiple ones with no success.
Can anyone tell me how I can fix this or at least point me in the right direction as to finding the problem?

And two more questions:
How much do you think boss or guitarcenter would charge to fix this?
And if I wanted to change the type of pedal inside the casing (ex: a diy compressor or something), what parts of the existing pedal could I salvage?

I think the cost of fixing would be almost as much as a new one.
As far as recycling parts, probably just the metal housing. I think the switch and pots might be soldered right to the board on those
Ibanez JS 1000
USA Jackson DNKY
EPI LP ltd
EPI Valve jr
and a bunch of pedals
BOSS pedals can be picky about adapters. Mine wont run on any of the multi voltage ones mine doesnt even tell the voltage, amps, or polarity. Your expected to buy the oficial BOSS adapter or fry it trying to find the right one. It will run on a 1spot. As for salvaging parts you might be able to use some of the internals. Depending on what you built. But if you build a pedal you will be using higher quality electronics than BOSS does. They are generally going to use the cheapest stuff available. And it would be really hard to put true bypass in a BOSS pedal housing.
The problem is most likely the amperage of the adapter, may not be enough for the pedal. Unfortunately, I'm not sure of what amperage you need.

Also, if it's a universal adapter, it may have a +/- switch on the adapter itself. Flipping it reverses the polarity of the current, which could also be the problem.
Adressing the issue of the right adapter: I tried a 1spot 9v adapter with both.

So I called BOSS customer support. Apparently they would charge $36 per hour per pedal to fix them, and charge me for any new parts. I said no thank you.

The thing is I really didn't need either pedal, I was really hoping to do a quick fix and sell them off for a easy profit. Oh well...
well theres a 5 yr warrenty
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Give me the circut board? please?