Help me Dx my MIG welder

I'm having a problem with my HF MIG welder. Help me diagnose it.

I bought it about 1994 or so, and it's made in Italy. I can't complain too much, as I've probably put 50 lbs of wire through it over the last 17+ years. It looks just like this one:

http://www.harborfreight.com/120-amp-230-volt-mig-and-flux-welder-97503.html

but it is 110V, has no wheels or extended handle and the wire cover doesn't hinge but just kinda fits in there. The controls/color/top handle sans extension are the same.

Anyway, the problem I'm having is with the wire feed. When I start welding, sometimes it will not push out the wire and I get "burn back" where the wire is back inside the tip and the arc is blowing from the tip. It is like the wire is getting a lot of resistance in being pushed out. It still is pushing wire out but it is much slower than the setting. This leads to the wire sticking at the tip. I can pull/push on the wire and then squeeze the trigger and the wire will come out at the correct speed, but when I start welding, it slows way down again. Not always, though. Sometimes it will work right. I put my thumb on the roller mechanism (when not welding, of course) and tried to slow it down and it has plenty of power, but when the wire is stuck or slow, the wheels are not moving fast enough. That is, the wire is not slipping at the drive wheels. I tried a new tip, no difference.

What are the signs/symptoms of a liner that has gone bad? What else might it be? I'm wondering if the motor drive circuit is going/gone out.

The one pictured above is available for $180 on coupon right now. If I can't figger out what's wrong with this one, I'm debating getting that, but then I'll have to rig up a 220V extension cord, etc. I'd rather fix the one I have. I'm about 95% done welding on this: http://grassrootsmotorsports.com/forum/grm/europa-frame-progress/39635/page1/ and I need to get this back online.

One time it was cheap ass wire - I got a batch that must have been a smaller diameter in places because I ran out about 10' of it, cut it off and it worked fine for the rest of the roll. I have been buying good brand name stuff from the local dealer and have not had that happen again.

That said, It is typically a sign that it is time for a new liner. I start to notice when I have to keep the tube close to straight to make it feed (any sort of steep curve between the gun and the unit causes slip). It is around then that I remember I'm on my 3rd or 4th 11lb roll... so consistent with your usage. I have a Miller so the parts are readily available for mine... but I don't see why they couldn't be used on any unit if you can't find stuff for yours. It is just like a specific diameter bicycle brake cable sheath.

If your HF MIG is the same italian unit as the Astro, Cebora, Daytona, Napa, marquette and many others it will have a plastic liner that will indeed cause your problem. I replaced mine with a wire wound Forney liner from the farm store down the street. Just look for a liner with an OD that matches the plastic liner. All you have to do is cut it to length and slip it into the push-locs. $10 fix!

As bad of a reputation that those old italian welders have, I feel they are much better machines than the current harbor freight models.

I had the 240V version of the one you hotlinked and replaced it with my $20 20+ year old swap meet 110V "Astro power MIG" and haven't looked back.

Humm. It does have a plastic liner. So my S/S (signs/symptons) are consistent with a Dx of Failed Liner Syndrome (FLS).

Are these liners fairly universal in size? That is, will my Italian HF liner be about the same as whatever is sold by everyone else in the same small MIG welder range? Is this a standard in-stock Tractor Supply item? TS is open on the weekends. The welder is at home, I drive by the welding supply store on the way home. The welding supply store is, of course, closed tomorrow and I really wanted to finish the frame (except for a body mounting bracket or two) this weekend. I eyeballed the liner OD but if there's like 5 different sizes, I'll have to measure it better than with the eyeball method.

I just bought the liner for the wire size I use (.023-.30 is what I keep in it) intending to modify the welder if neccesary to make it fit and it happened to slip right into place like it was designed for it.

Plastic/teflon liners wear pretty quickly. It will feel like a new machine with a new liner in it.

Looks like TSC has these in their stores: http://www.tractorsupply.com/welding-metalworking/welders/mig-welding/mig-welder-accessories/hobart-welding-gun-replacement-liner-023-in-to-035-in--3898486

$30 for a five pack.

Sounds like you have a solution, but have you tried wire lube? I've seen a spray can of that in a welding store...

Although, if $30 is a real solution, rather hard to bet that.

alfadriver wrote: Sounds like you have a solution, but have you tried wire lube?

If it gets on the wire it will contaminate the weld

In reply to Giant Purple Snorklewacker:

I would think so, too, but when real welding shops have it- there must be soemthing to it.

Agree with the liner suggestion since you have a few feet of wire through the thing. However, check the free roller to make sure it still spins. The free roller is the ne that is not powered by the roller but just pinches it against the driven one. I had that gum up on my Italian Welder once upon a time. Even if it is not gummed up, good to clean it up and add a dab of lube.

Thanks, NOHOME, I'll check that too.

From what I've googlezed, it appears that a metal Tweco MiniMig steel liner can be made to work by whacking the ends off and maybe adding some shrink wrap to the gun end. Also, a Miller Cricket liner may work.

There's a whole set of threads on weldingweb.com where people have been "tooning" these things, adding better motor control circuits, readouts, filtering caps, inductors, etc. I thought I was hi-tek, y0, with my muffin fan.

How do you like the HB Welder?

I have my eye on one from HB, or one from Eastwood

17 YO Italian Welder with FLS.

As a followup, I can confirm the diagnosis of FLS. I bought a Tweco metal liner at the local welding store on the way home yesterday, $20. I pulled the plastic liner out and put the new metal liner in, cut the ends with a cutoff wheel, smoothed them up, put some heat shrink on both ends and got it all back together. Welds better than new. And I have enough extra liner for an entire extra MIG, as I doubt I'll wear this one out in the next 25 years.

TIG, you mean the HF welder? I like mine. Go through the weldingweb.com site and see what others think. The Eastwood is probably the same with a different paint job. I used a Hobart Handler once and it had nothing on my HF, which, incidentally, is the 70 amp 110V input model.

Success! Great news and even better news that I wasn't wrong

Sadly the last US source for the wire drive parts for these seems to have dissappeared. I made a new tensioning/guide piece for mine out of steel and plan on doing the same to any other plastic pieces that crumble.

I got some Teflon tubing from the lab where I worked years ago to replace the crappy plastic liner that came with my Italian (Cerbora) made Daytona Mig. Wire fed like a champ after that.

I always use a wire cleaner/lube pad which really helps.

Wire cleaner thingies!

I've read of people using ear plugs to clean the wire. My wire is 308, so I'm pretty sure the rust level is quite minimal but non-existent.

I like the PTFE liner idea, but the PTFE store here is closed.

Thanks for all the help, guys. I'm almost done with the frame. Just a few more gussets and a bracket or two.

In reply to Dr. Hess:

Yep, the Harbour Freight. I have a new welder and air compressor on my wish list to buy this winter.

Thanks for the input.

The Harbour Freight store in Knoxville is my new friend. I bought a light weight aluminum jack there last year since I can't roll the heavyweight one around anylonger (back). Its great. I bought a winch for my trailer there also. Expected it to pull slow - but better than expected for $99.