Yeah, boredom does a lot to get prepared for such things.
I was struck with my noobness today when I was doing DMM checks on the PS box leads. I tested the Vout banana jacks on the box and the switch worked fine @ 19.3V reading. So, I flipped the switch..nothing, of course. Then, I checked V at the V+ banana jack and the common ground jack, and was surprised to read 9.6V. Well, duh...with the common ground tying the - on one 9V and the + on the other, and measuring voltage on the + side of that battery, through the jack, I was, of course, completing a circuit which included one battery. (Ya just have to put some thought into it)
As the Ophir is not using the common ground as a power source, it's of little concern, considering no circuit is being completed.
I'm saying these things as much as an explanation to myself as anything..