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.

[jtybt]

That might just be the ticket.

I took the pedal apart. On initial pedal movement, The pot begins to turn but the micro switch doesn't activate until about 1/4" pedal movement.

What does the micro switch do?

[everlastsupport]

The micro-switch is the on off switch, pins 1 and 2. Just like the trigger on the torch handle.

[jtybt]

Hmmm, so that doesn't sound like it would do anything good or bad, as long as it's working, huh.

Does it sound like changing the pot will do any good? Looks like I can cut away almost 2" in overall height from the pedal so I'll have to disconnect the pot and switch anyway.

Would connecting the wires in the same order work on a new pot?

[everlastsupport]

Hmmm, so that doesn't sound like it would do anything good or bad, as long as it's working, huh.

Does it sound like changing the pot will do any good? Looks like I can cut away almost 2" in overall height from the pedal so I'll have to disconnect the pot and switch anyway.

Would connecting the wires in the same order work on a new pot?

Most pot like that have the common in the middle, so it should wire up the same way. Just make sure the center in the common.

[performance]

OK,
1) what is your gas?
2) what tungsten are you using?
3) What amps are you trying?

Have you tried it with the tig torch switch to isolate the issue?

[jtybt]

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"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."
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I usually use the torch button with pulse but tried the pedal for this project. Just went back to the button. I get a harsh/strong arc at start-up sometimes but not the fireworks like with the pedal.

I just don't get that nice little 'ball of light' all the time. It's a pretty erratic starting arc no matter what I use.

[performance]

Flap wheel? Why are you sharpening your tungsten with something usually high in aluminum content i.e aluminum oxide? A harsh start can be from a sudden burst of gas. Increase preflow time. Also sounds like possible bad gas. 1/16 tungsten is WAY too small unless you are welding at something less than 20 amps, especially on aluminum. It will cause bad starts. I know what the "charts say" from the big guys, but they also recommend using pure tungsten too for aluminum.

[jtybt]

Never occurred to me about the aluminum oxide. I'll check. Otherwise, I was using my grinder. How about a angle grinder wheel.

I'll go play with the TIG after I finish buffing the cleats a little.

I have pre-flow set at about 10 oclock

[parkour]

I have had good success sharpening tungsten with an ordinary abrasive grinding wheel.
What I happened to pickup and was a Sait A24N-BF

[ogorir]

"1/16 tungsten is WAY too small unless you are welding at something less than 20 amps, especially on aluminum. "
1/16" should be good up to 65A or so on alu or about 75 on SS. you'll probably want to put a land on the end of the tungsten for the higher end of any tungsten size's operable range.

you also might want to back the amps off, but if you're using a high high-to-low pulse current ratio, 98A sounds about right (just too hot for no pulse).



the diamond wheel in harbor freight's chainsaw grinder refill kit works well for sharpening tungsten with an angle grinder (not my idea, I'll try to find credit, it was someone else on this board). I just clamp it in the vise on the welding table.

[jtybt]

I'll look for the diamond wheel at HF next time I go. sounds like a winner.

I think my initial gas flow was part of the problem. Seemed better if I started an arc when the post flow was going so there was a more steady flow. practiced welding a bead on the edge of 1/8" 304. Got pretty good control at low pedal after fiddling with the switch and POT. Gonna play with it some more. I just don't get enuff seat time to figure out all the little adjustments to make things go smoothly.

[Wrenchtamer]

I'm not sure how much the chainsaw kit costs, but you might want to check this out http://www.harborfreight.com/3-inch-...her-94071.html
It's a little mini grinder for 30 bucks. The on epictured is a little different than mine, mine has a knob on the front to control rpm. I made a little guide on mine to give a nice point on 3/32 and 1/16. It comes with one semi fine stone and one polishing wheel and had a little dremel type rotary attachment on it. (I took that part off.) the refill kits with new stone and polishing wheel are ten bucks I think. I bought mine a year ago and still on the first stone. I use it only for tungsten. believe it or not I have actually used the polishing wheel to finish up the tungsten and it gives it a nice chem-sharp type of point. Just have to hit it with some acetone or solvent before you weld but it works real nice.

[everlastsupport]

Charlie,

Run your gas at 8-10 if you're using our metric gauge, 12-14 otherwise, make sure there is no breeze of any kind..

Also, Mark hit the nail on the head. Bump the electrode size. The charts are not always your friend.

The gas is pure argon right? Is the tank a rental tank? The yellow ball sounds like bad gas or your electrode is contaminated.

I know this is a repeat, just want to make sure you weed out the problem.