I've just carried a second hand mixer deck home on the bus.

While waiting for my stop, I noticed that if I moved my hand near the left VU meter, the needle would swing. Not much, but a little. It only worked on the left one. I didn't have to touch the case. And no, it wasn't plugged into anything. I'd just ruled out random motion caused by me joggling the deck as I moved my hand when I had to get off.

It doesn't do it any more.