Mig welder problem

[Yondering]

Something's gone wrong with my Lincoln 175 mig welder in the past year or so, and hoping you guys can give some suggestions what to look for. I've been welding for 20+ years, but don't know much about the electrical side of mig welders and am not an electronics guy other than some general basics and theory.

This welder has always worked really well for me in the past, but lately is acting like maybe the duty cycle is really low. It'll start off a weld with that nice sizzling bacon sound, but after a short time (seems to vary with power applied) the sizzle cuts back to a soft hiss and the weld kind of beads up with very little penetration. It does maintain a spark during that time.

I'm guessing maybe some capacitors went bad, or ?? The welder is stored in my unheated garage; our weather is pretty mild here but temps have gone down to about 10-15* F in the last couple winters so maybe something froze? Just guessing wildly there...

Any helpful suggestions appreciated. I do know sending it back to Lincoln may be the best option, but maybe it's an easy fix and I don't know what I don't know.

[Dave C]

Sounds like you're right that a cap is failing. Cold does some weird stuff. My old tractor wouldn't start the other day. Cleaned points, replaced the capacitor, have sparks when shorting points, but no fire from 2 year old coil. Tried an old coil that had been in the warm garage, and it fired right up. Maybe moisture gets inside these things from temperature swings.

[Dedave]

Every mig welder I have pulled apart due to failure was because of metal dust shorting the board.

The other thing is that your liner may be dirty. That is real easy to test.

[Willy]

It'll start off a weld with that nice sizzling bacon sound, but after a short time (seems to vary with power applied) the sizzle cuts back to a soft hiss and the weld kind of beads up with very little penetration. It does maintain a spark during that time.

Not saying that this is the problem, but from your description it almost sounds like the wire feed is slowing down drastically. As we all know it is the wire feed rate which controls the amperage so a wire feed speed reduction could be the culprit here. This would be easy to check when the problem occurs just to narrow it down and eliminate that variable.

Does the machine return to normal later, how long? What triggers this problem, arc on time, gun or cable movement?

[markx]

That is a modern inverter based machine, right? With a switch mode power supply, not the old school iron core transformer, I assume? In that case the possible reasons for it acting strangely are so numerous that spotting the right one at a distance may be close to impossible.
But the more obvious and simple ones can be checked for starters: bad connections, dirty liner, worn tips, any obvious visible damages, conductive dust on the circuit boards, irregular feed rate of wire. If none of these is the reason, then it most likely is a problem with the power supply electronics. Or if one is lucky then it is the wire feed electrics department. Diagnosing and fixing that takes some electronical knowhow and at least a decent scope to spot any alarming distortions in waveforms.

Old school iron core machines are way more forgiving and foolproof in that sense. There are really just a couple of things that can be wrong with one of these and usually they are an easy fix.

[BigMike782]

It is a transformer machine. Sounds like caps to me.

[Yondering]

markx, I don't know enough about these to answer your questions about the type of machine. It's a Lincoln 180 that I bought new about 10-12 years ago. I couldn't tell you anything about the electronics inside.

Dedave, could you elaborate on the dirty liner and what I'd test?

Several of you mentioned iron dust; I can certainly take things apart and blow the dust off. I appreciate the suggestions.

Willy, it seems to return to normal within a minute or two, maybe less but I haven't timed it. The problem is triggered by arc time, not gun movement as far as I can tell.

[Yondering]

One more issue with this welder I'd forgotten about, which may or may not be related - I mostly use this welder with Argon/CO2 gas, but it has the ability to use flux core when current polarity is switched on the cable leads. It worked really well with flux core in the past, but last time I tried this it wouldn't weld well at all, mostly just fizzled and hissed without striking a good sizzling spark.

I don't know if that could be another symptom of the same issue, but thought I'd mention it.

[hermetic]

Dedave, could you elaborate on the dirty liner and what I'd test?

Have you ever fitted a new liner to this machine? if not, after 10-12 years of welding, this could be the problem!. Sounds to me like it is a wire feed problem too. Take the wire feed off the wire, and run the welder to see if you can hear the motor, or see the wheel slow down or run erratically. Take the liner out and blow it through with compressed air, but if it is the original liner, fit a new one!!

[hermetic]

also check the tension on the wire feed, and check the drive wheel slot for wear.

[Yondering]

Have you ever fitted a new liner to this machine? if not, after 10-12 years of welding, this could be the problem!.

I have not, but it doesn't get used a lot. Probably only 2, maybe 3 spools of wire since it was new.

[Willy]

The wire feed speed feed rate is what controls the amperage and by the description of having an arc accompanied with no penetration and a hiss it sounds as if the wire speed is slowing down measurably at that point.

Set the machine at a voltage and wire feed speed you know works well, verify this by laying down a short bead. Next while making sure that you aren't going to strike anything that is in the welding circuit, trigger the gun for 10 seconds and measure the amount of wire that has now exited past the contact tip. Multiply that figure by 6 to obtain the wire feed in inches per minutes. For example if 30 inches were spooled out during the 10 seconds and that figure is multiplied by 6 your wire feed rate would be 180 in./min.

Do a bit of welding to the point that the problem reoccurs, then instantly repeat the above procedure in order to determine if the wire feed rate has slowed down from the figure you obtained when all was working as it should. If the amount of wire spooled out is shorter than before you would have a feeding problem. Which could be as simple has a dirty liner, a contact tip, drive roll tension etc.

Let us know what you find and well go from there.

[v860rich]

On my 220 amp Lincoln mig welder if it's not used for a long period of time the wire will get an oxidized coating on it and not want to feed properly, act just like you describe. I unspool a bunch of wire and discard that.
I now have a felt wiper clipped on the wire just before the feed rollers, I spray the felt with PB Blaster or another lube so the wire gets cleaned before it enters the feed rollers, that will fix it for a while, at least until I forget to lube the felt again.

THANX RICH

[Dedave]

Dedave, could you elaborate on the dirty liner and what I'd test?

Have you ever fitted a new liner to this machine? if not, after 10-12 years of welding, this could be the problem!. Sounds to me like it is a wire feed problem too. Take the wire feed off the wire, and run the welder to see if you can hear the motor, or see the wheel slow down or run erratically. Take the liner out and blow it through with compressed air, but if it is the original liner, fit a new one!!

Sorry about the late getting back to you. I fitted alot of liners in alot of machines. Kinking is the first and most prevalent issue.
Easy test to start with is release the feed tension and push the wire manually with your fingers. It should move fairly easy.

The last liner machine I fixed was a lincoln small shop model. I was buying a guys bandsaw and we got to talking and his machine wouldn't work. Liner was clogged up. worked wire through a few times and pushed the dirt out the end. When I say worked the wire, you have to cut a nice square end and then pull it back into the liner and push it back out letting the blunt end carry whatever dust it can collect. Do not grease your liner.

To remove your liner, is fairly easy. pull the nozzle and diffuser from the gun end, unhook the torch from the machine. There is most likely some set screw holding the liner brass fitting on the feed end. Rotate the liner as you work it out. Usually a counter clockwise rotation helps if it is really gummed up and stuck, but generally fairly simple and straight forward. Do not just pull without rotation if it is stuck, you will stretch the liner and render it useless or unfixable. Think lawnmower throttle cable of yesteryear.

When installing the liner, it must be real close to proper length. Too long and it binds, too short and it will not sit into the diffuser proper and won't guide the wire as efficiently. When you pull the old liner, if you see kinks, most times they can be straightened if careful.

At 12 years old, definitely needs blowing out. But if the damage is done, new board is in order. Usually that can be seen with a good flashlight and magnifying glass. Look for burnt areas, resisters usually. I had a nice miller that I bought cheap that burnt up that way. Make sure you unplug the thing before pulling panels.

Hopefully the issue will be self evident when you pull the liner.

Caps, drive motors,power transformers/coils are hearty on these machines. Welder repair shops like to tell you that is the problem. Schematic for the boards are impossible to get unless you are an authorized repair shop and even then the information is lacking.

[markx]

I agree on the wire feeding setup being the most probable cause....after all this is the part of a MIG that works the hardest in mechanical terms. Erratic wire feed rate can cause these and similar symptoms. Caps are a possibility, but usually their capacitance does not fluctuate up and down or reset itself within a few minutes of idle time, it is more of a one directional process. Could also be the power supply for wire feeder, I've had a sneaky situation with one of these (cheapo noname): the wire feeder would work nicely when the machine was not under load. But when the arc was struck, the voltage would fluctuate and be pulled down enough to make the wire feeder act erratically, causing similar problems.