Welder died? Over duty cycle? How to fix?

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Welder died? Capacitor fried? What happened? --------------------------------------------------------------------------------I was working on a custom bumper for my K5 Blazer the other day when my welder apparently fried. I have a Lincoln ProMIG 135. I had it running flux core .035 on the highest setting. I had been welding up a storm when it started misbehaving in the middle of a weld. I replaced the tips & all, checked polarity, referred to the recommended settings on the sticker inside the access panel. Everything is correct. As I said, it died in the middle of a weld. I switched back to .025 MIG, same thing. I've been using this welder for about 5 years now.Here's the symptoms:Power is on.Wire feeds normal, as it should.It readily arcs. I'm welding on good clean metal.It has no power behind the weld. No penetration even on thin metal on the highest setting.You know how when you touch the tip to the metal (grounding out) when using flux it makes a distinctive low pitch hum... thats what it does all the time now.Did I burn out my capacitor? Transformer?How can I test the capacitor?I've got to get this thing running again & can't really afford a new machine.Thanks for the help!John O>.
Reply:Until someone more knowledgable chimes in I suggest opening it up and looking for any visual signs of a failure. Check the transformer theroughly for any scorch marks or melted enamel. Even get in there and smell for anything burnt *be careful of shorting the capacitor with your face* The only visual way to tell if a capacitor is bad(from what I know) is if the top is buldged out and theres any type of "material that shouldnt be protruding from it. Such as gooey stuff, or dried up stuff if its been a while. May even have a scorched look.
Reply:You may have burnt out a diode or two.Use a meter on the DC voltage scale between tip and work ground.When the torch button is pressed, it should read about what the OC voltage is stated as on the label.
Reply:Diode(s) would be my first guess as well.  If you don't get the proper OCV as Bluewelders described, check for AC voltage at the input to the rectifier assembly.If voltage is close to the rated OCV, the indication would be defective rectifier diodes.If it's not - as in nothing or not even close - the indication would be a failed transformer or current selector switch.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:I have a SP-135T it is close to what you have. I could not find a schematic for the ProMIG 135 so here is the web site for the manual with schematic for the SP-135T. If you disconnect the wire from the power switch this will isolate the diodes and capacitor. If it doesn't Hum reconnect the wire then disconnect the capacitor. This should tell you if it is the diodes or cap. http://content.lincolnelectric.com/p...r/im/IM785.pdfLast edited by Jackson; 07-21-2010 at 07:35 PM.
Reply:I found two for the Pro-MIG 135.http://www.mylincolnelectric.com/Cat...t.aspx?p=33703http://www.mylincolnelectric.com/Cat...t.aspx?p=33777MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:It looks like the welders are the same.  Good to know.
Reply:Thanks for the good suggestions!  I'll be pulling out the multimeter again tonight.  I'd LOVE to get it running again.John O>.
Reply:The OC voltage reads 27.5 of 29 advertized volts.  So, I'm guessing the diodes are fine.One possibly odd thing, I get 117VAC at the outlet & 100VAC on the input side of the diodes.Am I losing a few volts in the transformer (& is this normal)?  The capacitor doesn't look compsomised in any way, but it doesn't hold 40VDC either.
Reply:& do you know of any good places online where I can order parts?  The local welding shop wasn't very helpful.John O>.
Reply:The transformer takes 120vac and converts it to low voltage AC, like 12-24vac.You may have a meter that is messed up.
Reply:Using the wrong reference point (ground) for your meter will give you a wrong reading. On the schematic measure across the primary (H1,H2 = 110v) and the secondary (x1,X2) . This should give you readings like Bluewelders suggested. If you put your ground lead on the X1 point and put your other lead on the output of the selector switch (202) wire  using the AC scale you should see 4 different voltages ( x5 lowest-to x2 highest.) I would do this with the diodes/cap disconnected. With these parts disconnected (no load) your reading on the transformer output may be higher than normal.
Reply:the diode heat sinks are AC, the DC buss is the cap terminals.The diodes are pigtailed together and wires go to the cap and weld terminals.Quick test on the diodes is to remove the large pc board plug, one cap wire and the front heat sink transformer lead connection. This is the best way to isolate the diodes with out taking the diodes apart. If you lost one diode it is most likely the one in the back bottom.On the top of the large cap is a rubber plug. it should not be leaking or blown out or have a hole in it. if your unit is a tap switch unit check the switch contacts. you may have burnt the wiper. your heavy welding may have over heated the switch and melted the shaft.dirty or worn switch contact will make things worse.
Reply:Quite likely your mig gun is at fault here, what your getting out the end in arc, is very little current carried over the steel liner, not the internal copper conduit, which has likely pulled out of one or both ends. It doesn't much sound to me that the machine itself is at fault