I was able to get my PB520 working with a 1.3A@15V power supply from a cable modem (free). I cut the connector off of the dead original power supply and wired the orange/red wires to +15V; the black wire and braid go to ground. The blue wire is not connected.

IIRC the PB520 will run on any voltage from 12-18V. Don't try a higher voltage because the protection circuitry will shut down. I found this out by powering mine with an 18V solar panel that put out >18V when cold. As the solar panel heated up the voltage went down, and the PB started drawing power.