What is this wall wart from?
this is from my modem. input is 220v-240v AC
Can you take a picture of the label? I'm pretty sure you're feeding the board AC.
How about verifying with a multi-meter? If you don't have one you will need it sooner or later anyway.
Yeah I'd be wary that it doesnt say DC. The one I am using is from on an old switch and says DC.
My FB v4 came with a power pigtail - don't recall if I ordered it in addition or if it came with it. If you have one, just add some wire and test with your car battery real quick. You should be able to quickly confirm normal operation using the car battery as the power supply.
I wouldnt trust it, just use another wall wart or something that you are sure of. Doesnt make sense not to and blow up your FB...