PA140st arc stability

[joshuab]

This is probably a silly question, but have you checked the consistency of your mains power? Mains power is usually pretty solid, but given that two separate machines have had the same problem, it may suggest something outside the machine causing the issue. If your mains power shows steady when the machine isn't plugged in, another thing you can do is clip some tiny alligator clips to the prongs on the plug, then plug it in to the wall, sandwiching the alligator clips between the plug and the wall. I can usually get the plug in far enough to make contact while still leaving the alligator clips attached. This allows me (or a helper) to monitor the line voltage while welding. Obviously, use some common sense when doing this and don't electrocute yourself or anybody else.

If you care to remove the cover of your machine, you could also clip a multimeter on to the lugs where the power line goes into the machine. This would also allow you to confirm that your plug and your receptacle were wired up correctly.

[NWD43]

This is probably a silly question, but have you checked the consistency of your mains power? Mains power is usually pretty solid, but given that two separate machines have had the same problem, it may suggest something outside the machine causing the issue. If your mains power shows steady when the machine isn't plugged in, another thing you can do is clip some tiny alligator clips to the prongs on the plug, then plug it in to the wall, sandwiching the alligator clips between the plug and the wall. I can usually get the plug in far enough to make contact while still leaving the alligator clips attached. This allows me (or a helper) to monitor the line voltage while welding. Obviously, use some common sense when doing this and don't electrocute yourself or anybody else.

If you care to remove the cover of your machine, you could also clip a multimeter on to the lugs where the power line goes into the machine. This would also allow you to confirm that your plug and your receptacle were wired up correctly.

Thanks for posting. As soon as I hit "submit" I figured someone would mention mains voltage. The plug is connected to the entrance box via #10 wire and powers a variety of machinery including a 5Hp motor. I have not put a meter on it under load, but have verified 230 VAC at the outlet. I'll do it just to rule out everything.

Just thought of something, maybe I should try it on 110VAC just to see if there's a difference in results.

Neil

[Rambozo]

Out of curiosity, were all the accessories exchanged as well, or just the machine? The reason I ask, is that there was one report of bad connections inside the DINSE connectors at the ends of the cables. You can pull back the rubber boots to check those, although I really doubt that fits all your symptoms.
I do find that the machine will go much lower on 120 VAC so I tend to use that for low amp welding, but it works fine on 240VAC, just not quite as low. I have never had the overload light even blink. Does this machine have that lamp flashing, or was that just the first machine?
I know I did measure the OCV, voltage under load, and current, when I first got the machine, but I can't remember what they were, so I will have to check again.

[NWD43]

Out of curiosity, were all the accessories exchanged as well, or just the machine? The reason I ask, is that there was one report of bad connections inside the DINSE connectors at the ends of the cables. You can pull back the rubber boots to check those, although I really doubt that fits all your symptoms.
I do find that the machine will go much lower on 120 VAC so I tend to use that for low amp welding, but it works fine on 240VAC, just not quite as low. I have never had the overload light even blink. Does this machine have that lamp flashing, or was that just the first machine?
I know I did measure the OCV, voltage under load, and current, when I first got the machine, but I can't remember what they were, so I will have to check again.

I replaced the whole kit. Both machines work fairly similarly but the second one seems to be just a touch better. I know there must have been a cable problem in the past because the phone tech really grilled me about checking the cable connections. Just for fun I rigged up a ground cable that's about 4 times heavier than the std. one, and bolted the end to the workpiece just to see. Can't even strike an arc on the end of the ground cable! I'll wait a bit to see if there is any comment from the company folks before I call tech support again. Neil

[performance]

Not sure, but the issue still sounds like a connection issue.

[joshuab]

Not sure, but the issue still sounds like a connection issue.

Since the machine stick welds fine, maybe that points towards a problem with the TIG torch?

[NWD43]

Not sure, but the issue still sounds like a connection issue.

Assuming that it IS a connection issue, what sort of test do you recommend? I have tried two ground cables, a series of clamps, two Everlast tig torches, one Weldcraft size 17 torch (which works perfectly on my Lincoln), two different gas lenses, two sizes of cup, and two sizes of electrode. I'm running out of things to change and the performance is EXACTLY the same with any of the above parts. The problem seems to be in the lift-start circuitry. I have switched to stick mode and sacrificed the electrode a bit during arc-start, but the arc is stable and it welds OK.

Is there any other test that I can run? I'm a 30 year electrical design engineer with a lot of test equipment at my disposal so I can do almost anything needed and am not afraid to do some serious testing. It would be easy to simply send it back for a refund but I'd REALLY like to understand how my results can be so different from everyone else.

One interesting point: Most of the comparison tests I've seen are all being run at higher currents than what I need. Is it a lot trickier to use these machines at low currents?

Still hoping for that magically simple answer, Neil

[joshuab]

The problem seems to be in the lift-start circuitry. I have switched to stick mode and sacrificed the electrode a bit during arc-start, but the arc is stable and it welds OK.

You know, I didn't realize you were talking about the TIG torch when you said it welds fine in stick mode. You may already know this, but what you're describing is known as scratch-start TIG, and it's been a standard way of running a TIG torch off of a stick welder for years. HF is required for AC TIG, and as you point out, lift start or HF will help preserve your electrodes, but scratch start is tried and true.

One interesting point: Most of the comparison tests I've seen are all being run at higher currents than what I need. Is it a lot trickier to use these machines at low currents?

I have a PA160-STH. Not the exact same machine as yours, but not a high-end purpose-built TIG welder either. It's rock solid at whatever output I set it to, high or low. None of this wavering that you talk about. I don't typically weld at low amperage, and I use HF start when I do, so I can't speak to how its lift start works at low amperage.

It's so weird that you have two machines with exactly the same problem. It sounds like you're no stranger to welding, and like you have ruled out many of the obvious things except for the machine itself.

[joshuab]

Thanks for posting. As soon as I hit "submit" I figured someone would mention mains voltage. The plug is connected to the entrance box via #10 wire and powers a variety of machinery including a 5Hp motor. I have not put a meter on it under load, but have verified 230 VAC at the outlet. I'll do it just to rule out everything

Your mains is probably fine. I just figured it was worth mentioning. Trying on 110v isn't a bad idea. I'm sure someone from Everlast will chime in tomorrow, when they're back in the office. Or you could take the initiative and call in and ask for tech support.