Seller listed it saying "tested, correct voltages", but it is only 15 bucks. I've have Chou PSU's before, and no issues with power. I do have a dead one also, but it arrived that way (left in a cabinet). When you adjust the pot, do you see a change on the meter? I seem to recall that 12v will not change, but that could have just been me.
Welcome to the world of arcade collecting, pop'd your cherry early. The hobby where everything breaks.