PA140st arc stability

[NWD43]

I've just posted under "introduce yourself", and thought I should keep the technical details in a more appropriate thread.

I have just received my second PA140st in three weeks, and have seen the same problems with each machine.

SETUP:

Welding new, clean mild steel in a super nice environment using the tig torch supplied with the unit. Using a gas lens and either a 1/16 2% thoriated or a 3/32 lanthanated electrode with Argon at 10 CFH.

Running on 230VAC on a 50A breaker.

Ground clamp and cable are obviously new and attached securely to a cleaned spot on the workpiece.

The cables are attached properly, workpiece (+) and torch (-).

Output measures approx. 65 VDC at 10 amp setting, and 70.4 VDC at 140 amp setting.

PROBLEM:

An arc cannot be struck at a current setting under 17-18 Amps. There is a tiny spark when the electrode is lifted but no arc is sustained until the current control is past 17 amps.

When the current control is advanced until an arc can be sustained, the output current varies from low to high, and at lower settings it will extinguish at the low point. When the control is advanced to around 25 Amps the arc will sustain but the current varies. The problem seems to be worst at low settings and is partly masked at higher currents although the variations are still there.

The output voltage changes from about 9 VDC to 17VDC at a rate of approximately 1 to 2 Hertz measured at the cables. The high voltage corresponds to the stronger arc, and the low voltage occurs when the arc is smaller.

MORE INFO.

Machine seems to work reliably in stick mode, actually welds very well.

Problem occurs immediately upon start up and does not seem better or worse after a bit of warmup.

I can supply more details if needed, I've practically emptied a tank of Argon fooling with it......

Hope someone has seen this before, I'm completely baffled.

Regards, Neil

[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]

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.