Parker Metal Working: AC TIG not working correctly

[TurboMatt]

I'm looking for a little help regarding my Parker Metal Working AC/DC Tig 200. A little over a year ago I got this welder from a friend in a non-working condition. I shipped the welder to Parker for repair. A few weeks later the welder arrived back and sat for a month or two. When I unboxed it I played around with some scrap stainless in DC TIG, which worked perfect. I tried to weld some aluminum in AC and it worked great. I welded several aluminum pipes and some practice beads on some 3/8" flat aluminum plate. The welder started to act up so I called the guys at Parker and spoke with Phil Sr. He gave me a whole list of stuff to check/try. I've gone over everthing he asked and the welder still doesn't act right (which I'll explain).

While in DC every once and awhile (maybe 1 out of 10) the arc won't start. I'll see the high frequency start-up arc (if that's what it's called) but the welding arc doesn't start. I found that if I scratch the tungsten while this problem persists the welding arc will start.

Now the weird one. While in AC, the welding arc won't start if I try to weld aluminum, or even stainless (my workbench top) just to test. This is with the ground connected to the table or direct to the workpiece. If I ground to the table or the vise mounted to the table, I can start an AC arc nearly every time if I have the tungsten starting the arc through the large flat part on the back of the vise which is made of steel. To me, that makes zero sense as to why that should matter. I've welded aluminum many times with an older Miller syncro so I'm aware of how clean aluminum needs to be. What boggles my mind is how the welder will work perfect in AC on thick steel and won't even start an arc on stainless or clean aluminum.

Thoughts?

Thanks!
Matt

[longevity-inc.com]

Matt,

Check inside to see the high frequency board. There should be a stable and bright arc when the trigger is pressed. The optimum distance is about 30000ths. If you need more help, we have a dealer in Mesa, A2Z electronics that repairs units and also used to be affiliated with Parker before they jumped ship.

Their phone number is on our dealer page on our site. Ask for Jerry or Jim.

Thanks