After welding up more pop cans today, I came to the the conclusion that 10% EP with 250 hertz was the best setup with the tungsten ground on a very fine wheel. Also tried a fast pulse ( 300PPS to 500PPS ). The machine seems to pulse only on the DC half of the wave because it has more cleaning action on pulse. It did very good on both pulse and non pulse with not one burn through at those settings.