In the case of the Blacet PS500, you can run this right out to 500 mA,
and not worry about the "80% rule". We designed this supply to operate
at 750 mA, but derated it for cooling, European power, and low domestic
supply purposes. We test them all at +/-750 mA for an hour before
shipping.
Regards,
___________________
John Blacet
Blacet Research
http://www.blacet.com