Lincoln power arc 4000, wont weld.

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This thing is giving me fits. it's a straight AC welderMotor runs perfect. Generator worksI have correct voltage everywhere 120vac, 240vac and 62vac on the lead bolts.When I strike an arc at any amperage it will start the weld and then just quit like immediately. I've probed and prodded around and nothing I can see is broke, and I'm at a loss on where to look next.
Reply:I tried different rods also, it didn't help at all.
Reply:

Originally Posted by popsAwheelie

I tried different rods also, it didn't help at all.
Reply:

Originally Posted by popsAwheelie

This thing is giving me fits. it's a straight AC welderMotor runs perfect. Generator worksI have correct voltage everywhere 120vac, 240vac and 62vac on the lead bolts.When I strike an arc at any amperage it will start the weld and then just quit like immediately. I've probed and prodded around and nothing I can see is broke, and I'm at a loss on where to look next.
Reply:

Originally Posted by 52 Ford

What rods are you using? You said you tried different ones. Get a pack of fresh 1/8" 6013, get a good clean piece of steel (6013 likes clean material), and start around 90A and see what that does. I don't think I've ran into this issue with an AC stick burner. In the past year or two I've seen more than one person having that issue with lower priced DC inverter machines. Any chance you're trying to burn 7018? If so, I'd just drop that idea and just stick to other electrodes (6011, 6013, 7014, etc)Sent from my Lincoln Buzzbox using Tapatalk
Reply:

Originally Posted by Oldiron2

Is this a new problem on an old (previously owned) machine?What era was the machine from? Have you tried going to the Lincoln website and looking for a manual or troubleshooting guide for it? When you say the generator works, does that mean it puts out the correct amount of current under heavy load, or just that the voltage measures at the correct level? Might the conductors in one of cables, perhaps near the end, have a bad spot which causes an intermittent problem when it is moved, or heats up?Is the welding current produced via an alternator and is it separate from the power-producing section? If so, might the brushes providing the armature field current be worn and making poor contact? Or, are there lots of electronics (circuit boards) whose component(s) night have failed?Yes, these are guesses since I don't know that equipment and am not schooled in electronics or in generator work but have sometimes figured problems out anyway.BTW, pictures are always welcome and often helpful, if only in seeing what kind of gear is being discussed. Close-ups showing the workings can be very useful too.
Reply:double postLast edited by popsAwheelie; 1 Week Ago at 01:20 PM.
Reply:I found a service manual.I think I failed the second test on the slip rings to ground I'm showing an open circuit at all ohm settings and I changed test leads to be sure.I got 8.2 ohms on the test between the rings which is good.So what is this telling me? I know resistance to ground should be minimal so is the open circuit OK? On any load the motor will lug down pretty hard. A heat gun will drop the voltage from 130 to 115vac thats only 1500 watts.1. Conduct the test with the gasoline engineOFF.2. Remove the spark plug wire to preventaccidental engine kickback or starting.3. Isolate the rotor electrically by removingthe generator brushes. Refer to Figure F.2as you perform the remaining steps.4. Open the brush holder assembly cover.Squeeze the 2 tabs and depress the coverat the top with a screw driver or your fingernail. The cover will drop open on itsbottom hinge.5. With the 1/4” nut driver, remove the 2screws that hold the brush holder assembly in place.6. Slide the brush holder assembly out andlay it aside, held by the 2 wires attached.7. Measure the resistance across the rotorslip rings.A. Set the ohmmeter on the low scale(X1).B. Place one meter probe on one of therotor slip rings. Place the otherprobe on the other slip ring.C. Check the resistance across the sliprings. It should read 7 - 8 ohms.8. Measure the resistance to ground.A.. Set the ohmmeter on the high scale(X100,000).B. Place one probe on either of the sliprings. Place the other probe on anygood, unpainted ground. Use theground stud or the rotor thru-bolt.C. Check the resistance. It should readvery high, at least .5 megohm(500,000 ohms).If the resistance checks meet the specifications, then the rotor is oka
Reply:According to the manual I found online that shouldn't be the issue. if it makes power OK but won't weld, it is likely a bad connection somewhere, a faulty reactor (L1), or a broken rheostat lead (R1)https://www.lincolnelectric.com/asse...OLN3/im751.pdfMiller Multimatic 255
Reply:Thanks Louie. I thought it was ok on the slip rings but wanted to be sure. I printed out the testing procedures and am heading back out now. I'll update later.
Reply:The first thing I do is clean the slip rings and brushes.Dave

Originally Posted by popsAwheelie

This thing is giving me fits. it's a straight AC welderMotor runs perfect. Generator worksI have correct voltage everywhere 120vac, 240vac and 62vac on the lead bolts.When I strike an arc at any amperage it will start the weld and then just quit like immediately. I've probed and prodded around and nothing I can see is broke, and I'm at a loss on where to look next.
Reply:Well, the motor died a spectacular firey death. She didn't have enough left in her to weld. I've found a rebuild kit so I'll go that route I'll check back in after the rebuild and hopefully she will weld.