I have a set of LED christmas lights that I am trying to start a project with. The LED string comes with a power cord which is an A to D rectifier according to the manual that comes with the lights. A schematic of how the lights are hooked up is attached. I would like to hook up the supply to an oscilloscope to see what the waveform is like (I'm assuming there is some sort of PWM going on). I tried before, and began by trying to hook the ground alligator clip of the probe to the negative terminal of the output. There was a massive bang and flash of light, the fuse inside the lights power cord had tripped as well as seemingly fried whatever was inside because every time I plug it in after that the fuse trips. Luckily it seems the oscilloscope still works. What did I do wrong? How can I hook up the rectifier to an oscilloscope correctly?