How do I balance this brake?

Bought this bike used about a year ago. It came like this from the guy who sold it. Bugged me, but it pretty much worked and the price was good.

I still want to fix it. If I try to tighten the brake wire, the right hand side brake pad won't disengage from the rim. I've checked the little pins that hold the springs in place and they're both plugged into the middle hole on the little bits welded to the forks (sorry, I don't know the correct terminology).

I've always assumed these sort of brakes should be self-centering, but evidently they're not.