I don't have one of these units, so I can't tell you for sure, but I can make an educated guess.
With only a few rare exceptions that I've seen, DC power adapters generally have the center conductor (or the tip) as positive, and the outer exposed conductor as the ground/negative. This is done so that the live power contact (the positive) is as minimally exposed as possible to avoid short circuits.
To avoid damage to your unit, I would wait until you get some more confirmation before you configure and plug in a generic/replacement power adapter.