== Dissect an adapter
I got some ultra cheap USB power supplies from Ali Express. The price was simply slightly to good to be true, so brought one along to RevSpace. Look at what's inside:
The biggest problem appears to be that a 300+ V DC line runs perilously close to the USB connector (near C4). Probably not something to use in moist environments, such as the spark shack. Or maybe if you want to see sparks, one to use in such an environment.