PowerPro 256 makes HF but wont start arc

[acannell]

Still very happy with my PowerPro 256 and I have made alot of money with it. Finishing up some production welding today (TIG, 115A, AC) and the arc suddenly went out. Hf working, still seeing the non-stop lightning storm, just the arc wont start.

If I leave the machine off for a few minutes, I get another few seconds of arc, then it stops again.

I tried sanding the points and it didnt help.

I also tried replacing the MC14053BCP on one of the daughterboards that has previously fixed similar issues for me..no change.

Any ideas? I have a full suite of electronics test equipment so I can get in there and do whatever needs to be done. I'll make sure to report back what does an does not work so others get help from it as well.

EDIT: whoops..welding mode is AC not DC. Also, note that I have not changed welding settings in the past year besides main current level.