Reminds me recently of a wallwort transformer. Had two 24v 500ma ones from different manufactures but looked identical on the outside with same plug. One I used plugged in would cause the nastiest RFI I have ever experienced. Thought it wasn't that big of a deal as I was using it on an audio device until I used it while transmitting and it caused my transmitter to hum like crazy. After pulling out hair and going nuts I remembered I had the other almost identical one and swapped them. Problem gone!
It makes me wonder sometimes how this shit is built. Sure I can open it up and investigate but there are times even when doing so I find myself stumped. It's like the chinese have some special ability to make the most noisy RFI devices feasible, and I couldn't generate that much RFI if I tried and I know how to build electronics that can!
Food mixers have a special place in my heart though. My mother had one when I was a kid and back when we had cable TV, yes cable.. not antenna. When she'd fire that thing up to mix stuff the TVs in the whole house would get visual lines going through them. I could hear the motor through the audio on the TV. Still no idea how such a simple device caused so much RFI. Kind of astounding to me now considering what I know about transmitters. All I can figure is that the thing was a giant spark gab transmitter motor somehow. Remember every weekend she'd make mashed potatoes and use it and... there goes The Simpsons for 10 minutes lol.