I have a 250ex. Been welding steel and machine running perfect. Today I decided to weld aluminum here is where the problem starts. Welds fine but when I back off the pedal to finish the weld it sputters and pops and won't hold a stable arc. This seems to happen about 20 amps or less. If I start with low amps it sputters then also. Below is some things I have tried
1. Sharpened tungsten properly made a mirror smoothe finish
Also left rough finish same results
2. Ran from 8 to 30 scfh. No help
3. Balance and hertz different setting no help
3. Ground directly to work price. No help
4. Changed torch parts. No help
5. Cleaned metal acetone stainless brush. No help
6. Gas is flowing from torch as it should
7. Argon is down to about 750 lbs.
machine is about 2 weeks old. Welds steel just fine down to minimum amps
High freq . works every time. Any ideas???