Hard tig arc starting using pulse when restarting a bead

I've been welding lots of aluminum lately and so I've run into a situation that gave me fits. I think I found the answer to the problem but I would like to get another opinion.

I often have to re start a bead as I have to get another tig rod or rest a bit so I have to stop welding and re start the weld. Some of the welds are near an edge so I've been using pulse. Using the pulse, I have noticed that when I am welding in an area that has lots of welds near each other and lots of cleaning going on, oftentimes the arc with my Powertig 250EX will not re start on the white area of the aluminum where cleaning action has taken place. I do not have the problem when pulse is off. Using a foot pedal and 3/32 2% lanthanated on a Powertig 250 EX with amps set at 125 on 1/8 inch aluminum.

I wire brushed the white aluminum oxide off which seemed to have solved the problem. One other thing I did was increase the amperage so that the arc would start no matter what. Even without cleaning, the arc started but it was erratic with a spark at first then the arc.

So my question is this. Not having used a tig machine before with pulse, does pulse cut the available amperage in half when in use? Anyone else run into this?

What is the setting on your start amps knob that may help with a blast at the start.

Starting can be affected by pulse settings for sure. However, it may need the points may need to be reset.

Marks, got the fix to your problem. It's the points, you just need to reset them. Mine started the same way and eventually got to the point where I was doing lift starts. I reset my points and everything was good again but it happened again after about 35-40 hours of weld time. No biggie, I just consider it regular maintenance.

Is there any information online on how to re-set the points? Or do I have to call tech and have them walk me through? Maybe a video?

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Originally Posted by Steve

Is there any information online on how to re-set the points? Or do I have to call tech and have them walk me through? Maybe a video?

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Steve,

The points on the PP250 are located in the right front corner of the machine. To get at them, you need to remove the back bezel, the carry handle and the sheet metal cover. That part is actually quite easy. There are some pics of the points somewhere on this site.

They can then be "accessed", but it's tight. You adjust by bending them. Measure with a feeler gauge, ~ .035 IIRC.

However, you have the 250EX. Not sure if the points are located in the same general area on that unit. Maybe someone else will chime in.

rivets

A call to tech support can make things a lot easier, and help you avoid any pitfalls.
.035 is a good setting. Each unit, will have a slightly different "like". Everything though identical is different, if that makes any sense.

here are the points on my PM256 I would think your are similar

have fun
Tom

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Originally Posted by acourtjester

here are the points on my PM256 I would think your are similar

have fun
Tom

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Thanks Tom. The points I believe are near the front of the case as I can see a blue spark when the machine is welding. I figure that is the points arcing. I will though call tech support to make sure I'm doing it right for the first time.

Points. I remember when cars had them and were adjustable with one screw. The good old days.

If you found the HF spark, you found the points.

Left side of the unit (looking from the front) towards the front of the machine, where all the sky blue caps are behind it. It is on the HF flyback board. It is mounted upside down and looks like Tom's picture.

Let the unit sit for 5 minutes unplugged it before putting metal between them. .035 - .040 you should see much better arc control on the AC side.

Thanks. Yeah, I know about letting it sit. Capacitors have a nasty habit of shocking the daylights out of you if you are not careful.

I am a ham and so when I work with capacitors, I always short out the caps so I don't get juiced. It got me once and I'll never forget it. A lesson well learned.

Steve,

Yeah, HV AC caps will for sure teach you on the first try. But that should do the trick for you on the start control, make sure they are lined up straight too. Sometimes they are bumped in final assembly when the front panel goes on. Call if you need us.

Is 5 min enough for the caps to die down? I have cams in motor speed controller from my model airplanes that would take about 30 min to die down. Are there any other safety precautions to take if the cover is taken off of one of these machines?

5 minutes should be fine, 10 better just in case.

Depending on the units. If there are plastic bezels on the front and back, the unit comes apart from the back normally. If no plastic bezels, the cover should be obvious and lift straight up.

Remove the back bezel (and handle on some) then the metal case, slide the case back about 2 inches and lift up to remove.

We recommended a call to tech support. So call in if you have a question or need help.