Lincoln SP-125 Plus wire feed problem

[MAC702]

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?

[MAC702]

The code and serial number is 10260-U1970715354.

[cruizer]

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.

[cruizer]

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.

[gangel99]

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.

[MAC702]

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.

[MAC702]

It does not have a spot/stitch panel.

[MAC702]

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.

[cruizer]

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).

[Bodybagger]

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.