Current from my amp footswitch. Can I use it?

[Le québécois]

There is 15 V DC coming out of my old Peavey amp at the tip of the stereo cable associated to the footswitch (to change channel of the amp). Could it be use to power my pedal board? Have you try that and do you have any idea of how much current is available. It is not mention in my user manual. I know it can light up LED.
Is there a way to test the max mA available without destroying it! It's a Express112 from mid 80. I was not able to get the schematic through google.

thanks 

[R.G.]

If you pull enough current, it does the associated switching that the amp does when you ground it. It's not a generalized power out pin.

[Le québécois]

I knew it was to good to be true!

thanks for helping