Erratic start with foot pedal

[jtybt]

225 LX

With initial depression of the foot pedal, there is popping and a big ball of yellow light. When I press way down, the arc smooths out. The pedal seems to work OK at the last couple inches of travel.

What's wrong?

[performance]

Contamination of the tungsten sounds likely.

[Wrenchtamer]

Agreed (mostly). In my experience, it could also be a gas issue. It would be helpful to know what type of metal you were welding. You shouldnt see a difference in the color of the arc, even if there were a problem with the current input from a faulty footpedal. As Mark said, if the tungsten is slightly contaminated, you will see the difference when you initiate the arc. Then it might seem to smooth out as the amperage increases. So I would suggest you clean your tungsten real well and make sure you have a little shielding before you start welding. have you tried using the 4t mode?

[jtybt]

Cleats for boat. 1/2" 316 tubing to 1/8" 304 base plate. 2T 98amps straight argon @8L. 1/16 Thoriated. Everything cleaned with lacquer thinner. Sharpened on grinding wheel. Probably the cause of contamination.

Starts off like fireworks. Stuck and broke the tip off the tungsten and had a relatively clean start. Gonna try sharpening on a new flap wheel. Ran out of 1/16 tungsten, going to 3/32.

[parkour]

If those steps do not clear up the problem, try disconnecting the foot pedal from the machine and using an ohm meter to measure the resistance between pins (3, 4) OR (4, 5) as you slowly and smoothly depress the pedal. If the reading is not slow and smooth, the pot might be bad. Pots in general seem to be really hit or miss on whether or not they have any bad spots.

[jtybt]

Better but still erratic at start-up. If I punch it and back off it's better. Probably just can't try aluminum cans.

[Timberwolf]

Do yourself a favor and get a $2 50K POT at radio shack. Much smoother and you won't regret it.