open ground

In a follow-up to my previous thread Venue outlets have open ground. What does that mean? I thought I would post a poll to see how many people test the electrical outlets before hooking up their equipment. I have a little gizmo similar to this that you can get at any hardware store: Did you...

So, at my last gig I noticed that when I turned on the mains with the PA turned off and nothing going to them, there was a huge hum coming from them. So, as I had a handy electrical outlet tester in my kit I decided to test the outlets where the band plays and plugs into and found that there is...