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Lincoln SP-125 Plus wire feed problem

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  • Lincoln SP-125 Plus wire feed problem

    A good friend of mine was given an old SP-125 that wasn't quite working right. He replaced the gun, but now that I'm back I've checked it out and here's the issue. When you pull the trigger, you'll only get it to attempt to feed for a few seconds before it stops, even though you still have the trigger pushed in. Furthermore, while it is driving, you can adjust the speed dial all you want but it does not affect the speed at all.

    So I am guessing that it is a component on the circuit board. Any of you repair experts know which one, and is it something I can replace myself?

  • #2
    The code and serial number is 10260-U1970715354.

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    • #3
      Does it happen to have the spot/stitch panel?

      Anyhow, after a little reasearch, I can't bring up the board schematics as it is an obsolete machine, suprize, suprize. However the the board is still availble for it it's # is 9SG2314-4. Should be had for around $250 US.

      Lincoln Cleveland has a bunch of them.

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      • #4
        I know you said you have a new gun, but for my composure, remove the machine to gun trigger connector and jumper those terminals out with a piece of wire or a paper clip.

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        • #5
          Don't spend $$ yet

          Apologies if you have already done this but I'd check the mechanical components first. I have an SP135+, a slightly newer version of the 125+. It usually feeds OK but every once in a while it will go in fits and starts. The problem is usually too much pressure on the nut (maybe a wing nut) that holds the wire spool in place. But check the whole feed path - only takes a minute or two.

          The feed goes from the wire wheel through a nozzle looking thing that aligns the wire with the feed roller. The bottom roller has grooves and the top roller is pushed down on it to apply enough pressure so when the roller turns the wire gets forced through the gun.

          On mine the top part of the feed roller is a wing nut pressing down on a spring to apply pressure to the top part of the roller. This has to be screwed down enough to pull the wire off the reel and into the gun. If it is too loose it can cause the problem you have.

          As for the wire spool nut -- this has to be tight enough to keep the spool from turning when you stop pulling wire. If it is too loose you get a birds nest, if it is too tight you get fits and starts.

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          • #6
            It's not a tension or spool problem because I conducted my tests with the tension roller hinged away, so all it had to do was turn the drive roller.

            I will test with trigger bypassed and report back. I'll probably take the sheet metal off and see if anything is obvious.

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            • #7
              It does not have a spot/stitch panel.

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              • #8
                With trigger wires completely bypassed, the problem remains. In fact, it's worse now and the drive rolls will barely move now.

                At $250 for a new board (assuming that's the problem) I'm better off telling him to spend $160 more and just get a recon HH140 from Toolking.

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                • #9
                  Really better off sending to a good repair facility and getting them to verify the problem, or your just chasing your tail.

                  It's usually just a zener diode that blows open (A $0.01Cent part).

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                  • #10
                    I've seen those motors suck enough grinding dust into it to slow/stop it. My Lincoln pro mig 175 did that and it made the cooling fan grind to a halt, but I noticed the dust on the drive motor on another occasion after I dropped a wingnut and it got sucked onto the drive motor.

                    First, see if the drive wheel will turn with a couple ft-lb of torque. It's geared down, so don't apply any more torque than this. If it doesn't turn, or sounds gritty when it turns, take the motor assembly off and clean the grinding dust out.

                    My drive was sounding labored and loud before I did this, after a few years of heavy use. This fixed it right up and taught me to shut off my machine before grinding.

                    80% of failures are from 20% of causes
                    Never compromise your principles today in the name of furthering them in the future.
                    "All I ever wanted was an honest week's pay for an honest day's work." -Sgt. Bilko
                    "We are generally better persuaded by reasons we discover ourselves than by those given to us by others." -Pascal
                    "Since we cannot know all that there is to be known about anything, we ought to know a little about everything." -Pascal

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                    • #11
                      Were all on a miller site right? LOL!!!

                      A lincoln SP? Poor fella!

                      Just a lil kidd'n around!

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                      • #12
                        The latest is that there is a local guy with some experience replacing the "usual" component that causes this symptom, so he's taking a look at it for us.

                        If it comes to a $250 board, it'll get sold for parts, or stored while I look for a parts machine, and I'll get him a recon Hobart for when he's not able to use my machines.

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                        • #13
                          Originally posted by cruizer View Post
                          Really better off sending to a good repair facility and getting them to verify the problem, or your just chasing your tail.

                          It's usually just a zener diode that blows open (A $0.01Cent part).
                          I know this is an old post but can anyone elaborate on the location/sze of the zener diode that causes the feed problem? With the tension bar up and off of the wire, the feed wheel will turn when the trigger is pulled as long as the speed is 3 or less. When the speed is turned up past three the feed will move about an eighth of a turn and then stop while the trigger remains depressed. Very frustating

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                          • #14
                            Originally posted by cruizer View Post
                            Really better off sending to a good repair facility and getting them to verify the problem, or your just chasing your tail.

                            It's usually just a zener diode that blows open (A $0.01Cent part).
                            Good advice. What I would do and before spending $250 plus for a circuit board is disconnect from the power and examine both sides of the CB with your glasses on or a magnifying glass. IF there is a blown diode or other part you can usually see it cracked, burnt or otherwise. Find out what the specs are on the part and either pay someone to replace or get yourself a really small soldering iron (15-25 watt) at Radio Shack and some .032 rosin core solder.

                            Your circuit board may have a coating that prevents you from soldering or de-soldering anything. I usually use a small screwdriver sharpened to remove that coating.

                            Find a old PC board someplace and practice on before trying on your good one. Solder wick works great for removing the old solder. I usually just cut the defective part in half with a small pair of side cutting pliers and de-solder each lead. IF Its a diode there is a right and wrong way to put it in.
                            Last edited by wmgeorge; 08-25-2014, 08:24 AM.
                            Miller MultiMate 200 MIG/ Stick/TIG
                            Retired
                            Journeyman Refrigeration Pipefitter
                            Master Electrician
                            Amateur Home shop Machinist & Welder

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                            • #15
                              Originally posted by wmgeorge View Post
                              Good advice. What I would do and before spending $250 plus for a circuit board is disconnect from the power and examine both sides of the CB with your glasses on or a magnifying glass. IF there is a blown diode or other part you can usually see it cracked, burnt or otherwise. Find out what the specs are on the part and either pay someone to replace or get yourself a really small soldering iron (15-25 watt) at Radio Shack and some .032 rosin core solder.

                              Your circuit board may have a coating that prevents you from soldering or de-soldering anything. I usually use a small screwdriver sharpened to remove that coating.

                              Find a old PC board someplace and practice on before trying on your good one. Solder wick works great for removing the old solder. I usually just cut the defective part in half with a small pair of side cutting pliers and de-solder each lead. IF Its a diode there is a right and wrong way to put it in.
                              Thank you for the reply and advise. I will give it a good examination.

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