It should work. The reason being that even though the PS you have is capable of putting out 600mA of current, the device will only draw 500mA of current. You'd only have to worry if you tried using a PS that is capable of handling less than the 500mA the device draws.
To provide an example, I regularly use amateur radio equipment that draws about 10A when transmitting. When it's receiving, it only draws a few hundred mA. Yet my 20A power supply has yet to fry the equipment.
As long as the PS is rated for a higher amperage than what the scan converter will draw, you should be all set. Just make sure the polarity is correct when you hook it up!
JW