I'm really late on the reply chain, but hopefully you'll see this. I wonder if there should be an inductor coil on the power cable. It sounds like some AC is g

I'm really late on the reply chain, but hopefully you'll see this. I wonder if there should be an inductor coil on the power cable. It sounds like some AC is getting through, and an inductor (which is essentially an electro magnet) basically shaves it off. That's what the mystery box or tube is that you see on some other adapters and sometimes on accessory cables for things like keyboards with built-in USB ports. Basically the higher the current, the more magnetized it becomes. Magnets are polar, which makes it behave a bit like a one-way resistor so AC can't flow through.