Tips & Tricks / Troubleshooting
Tips & Tricks - #1
So Your Lincoln SA-200 Has Stopped Welding - For No Apparent Reason
The first thing to check is the obvious - your leads, or more precisely your lead connections. If you’ve put a whip on your stinger lead, be sure to check that too.
If those check out fine, meaning that they’re clean and tight then you’ll need to check the exciter next. Plug your grinder into the 115v receptacle and see if it has its full potential. Does it spin as usual, or does it take awhile to get up to speed? Or does it work at all? If it is working satisfactorily, then the problem is not in your exciter.
If your grinder doesn’t work or is slow, we need to check your exciter. The next thing to do is to shut down the engine, and remove the exciter brush cover (the little dome sticking out of the front). Inspect the two brushes, which are the carbon rectangles with copper wiring connected to them. Are they long enough? To check this you have to remove the load spring that keeps them pressed to the armature. Is the brush so worn that it lets the load spring ride on the brush holder instead of the brush? If so, it’s time for new brushes. These are components that you would be wise to have spares of readily available. (And not riding somewhere in the bottom of your toolbox, under all those heavy tools.)
If the brushes are long enough, and riding smoothly in the holder, the next step is to inspect the armature commutators. These are the copper bars that spin, that the brushes ride on. Are they black? Or just plain tarnished? If so, ideally you should take a stone to them. If no stone is available (or it was riding under all those heavy tools and is now chunks and dust) then some sand paper will suffice. Use real sand paper and not emery cloth. Emery cloth is coated with a metal oxide and can short your armature. Clean those commutators until you see some nice pretty copper showing. Install the brushes and start the engine.
When it’s running, it’s normal to see some light arcing under one of the brushes. If the arcing is heavy, or the sparks want to follow the armature around then you may have an armature problem.
This is just a quick field fix. If you still have no weld output, you need to bring the machine in to the shop or be comfortable with a DVOM.
Tips & Tricks - #2
So Your Lincoln SA-250 or Classic 300 Welder Has Quit Welding - For No Apparent Reason
It’s so easy to overlook the obvious that this can’t be over stated; check your leads first! Make sure those connections at your machine and at the ends are all clean and tight.
If your leads are ok, shut down the engine and remove the exciter cover. On the small body welders, this is the end that’s poking you in the belly when you’re starting your welder. There is one large pan sized cover. Remove the 4 screws that hold it in place and then pull it off.
On the big ‘boat sized’ SA-250’s you either have to remove the plate below the control panel, or, if you can’t get to the plate (as in a truck mounted welder) just work from both sides of the machine.
There is an upper and lower half to the cover that is over the exciter frame. There will be 4 to 6 screws holding these two covers in place. Remove the screws and remove the upper cover. Now BE CAREFUL when removing the lower cover that it doesn’t make contact with the battery, which is parked right underneath it.
Here you’ll be checking the brushes and the slip rings. First see if the brushes are worn down to the point where the springs are riding on the brush holder. If they are worn down, you’ll need to replace your brushes.
99% of the SA-250’s have an A/C exciter, so these have an exciter rotor instead of an exciter armature - so they also have slip rings. Now check if to see if the slip rings are highly tarnished, or are covered with goo. I’ve found that in the snow months the slip rings and armatures often get covered with a black ‘goo’ that prevents contact. This goo is from the magnesium chloride that is put on dirt roads. It gets up inside your exciter housing and when it gets heated up as you weld it spreads itself nice and evenly around your exciter armature/rotor, not allowing them to make electrical contact. In any case, if your slip rings are gooed up with mag chloride, or just tarnished you will need to clean them off.
The type of stone that I use for the rotors is different than the ones used on armatures, because the slip rings are brass instead of copper commutators. The stone for the armature is softer, and creates a dust that helps to seat the brushes; whereas the stone for the rotors has a coarse side and a fine side. You use the coarse side to clean, and then the fine side to smooth. This is done with your engine at its idle speed.
If you have a rotor, but no stone available (or it was in your toolbox and is now pounded to dust under all those heavy tools) you can use an emery cloth to clean off the slip rings - with the engine shut down, of course. After getting that brass to show its pretty face, be sure to blow off any of the material that came off of the emery cloth - and then reinstall your brushes, start your engine and check your weld output.
If it’s there, happy welding to you. If not, shut down the engine again and check the little fuse that is on the inside of your control panel at the lower right side (as you’re facing the panel). You’ll need to use a DVOM (Digital Volt Ohm Meter) to check this.
Park the dial of your meter in the ‘Ohms’ position (and if you have a DVOM that sings to you when it’s showing a short, so much the better). Check your fuse at both the connectors on either side of the fuse. It should read almost 0 on your meter. The reason I say to check at the connectors and not just to check the fuse is that corrosion can cause the fuse not to make contact with the connectors. If you read very high ohms, then pull your fuse and recheck it. If open, replace it. If it’s ok you’ll need to clean the fuse holder so the fuse can make the connection and let the current flow.
If the fuse and connector check out fine, then it’s time to go deeper. You are about to enter the rabbit hole, so only do this next process if you are genuinely comfortable and familiar with using a DVOM.
Beside the fuse that you just checked is a little box, about 1 inch square with 4 connectors on it. This is called a ‘bridge rectifier’ and those connectors are diodes; meaning that they only allow electricity to flow in one direction. On 2 of the 4 connectors are there yellow wires - these are for the A/C current that is coming out of the exciter. Leave these intact. The other two wires are the positive and negative for the D/C. You will be removing these one at a time in order to check the rectifier.
Remove the first of the D/C (non-yellow) wires. With your DVOM, hold the positive lead onto one of the yellow wires where it connects to its spade, and hold the negative lead onto the vacant spade that you just took the D/C wire off of. This should read either very high ohms or very near to 0. Write down the reading. Next, switch the DVOM leads so that you are holding the negative lead onto the same part of the yellow wire, and the positive lead onto the vacant spade.
If you got a high ohm reading the first time, now it should read very near to 0. If it was near 0 before, it should now read very high. Write down the reading. Reconnect the D/C wire to the spade. Now repeat everything that you just did above for the other side - meaning both the other D/C wire and the other yellow wire. Remember to reconnect the D/C wire when you’re done. You should have gotten the same readings from this side that you got from the other side. If your meter read 0 or ‘Open’ on all the tests you need to replace the rectifier.
Tips & Tricks - #3
So Your Wire Feeder, Or Wire Feed Welder (MIG) Keeps Burning Back The Wire
This little tip isn’t brand specific because these types of welders all have the same basic components. If your wire feeder or mig welder keeps burning back the wire to the contact tip, and no amount of heat adjustment compensates for it, then you most likely have a wire feed problem.
In case you’re not familiar with how to set your drive tension I’ll go through a quick test now. First be sure that the wire coming out can’t make electrical contact with anything you’re working on. Now, with your machine running, hold your gun nozzle about an inch from either a work bench or the floor and press the trigger. As the wire comes out, allow it make contact with the bench or floor. The wire should come out, and after it hits the surface it should start to curl around. It should make that curl and just keep feeding. If not, then try and adjust the tensioner on the drive unit itself. This is located where the spooled wire goes through the drive wheels. Try turning the adjustment clockwise about ½ to 1 full turn to increase the tension, and then retest. If this worked, great! Happy welding to you. If not, then the usual culprit is the gun liner.
Gun liners are usually made of steel for steel wires, or nylon for aluminum wires. In either case the gun liner needs to be removed for you to check it.
Turn off the machine. Cut off the wire that is sticking out of the contact tip, and then remove the contact tip. Now release the tensioner. From here I personally prefer to reach in and turn the spool by hand to order to rewind the wire that is in the gun, though some people just cut off the wire behind the drive unit and then pull the wire out after they remove the gun. I quit doing it that way because I got tired of tripping over the wire that ended up on the floor after it pulled out, and was left to be picked up later.
When you wind the wire back onto the spool, be very careful to stop before you reach the point where it comes out of the gun. Move the spool very slowly, so you can catch the end as it comes out and then secure it to the spool. If you don’t catch it, you’ll end up with the spool rapidly unwinding itself. It’s almost like a practical joke you pulled on yourself, funny - but not.
Now, most manufacturers make it pretty easy to remove the gun. Usually it’s just a thumb screw right where the gun goes into the drive unit. Loosen the thumb screw, remove the trigger wires from the machine and remove the gun. The trigger wires are either independent plugs or they’re in a connector that needs to be removed also.
Now that the gun is removed, I usually clamp it LIGHTLY into a bench vise. There I can lay the gun out straight along the bench. Remove the nozzle, contact tip and gas diffuser from the gun. Note: some guns have a set screw in the diffuser that helps hold the liner in place, which will need to be loosened. If so, loosen that set screw. Next, at the end that went into your machine there will be another set screw or cap that also holds the liner in place. Loosen this also. Sometimes you will need a pair of pliers to pull the liner out of the gun.
After you have removed the liner it usually becomes obvious why the wire was not traveling out of the gun smoothly, as most of the time you’ll find a kink in the liner at one end or the other. If this is the case, replace the liner. You may want to try and straighten and reinstall it, but this rarely works because what looks straight to you still may not be straight enough allow the proper clearance for the wire to pass through unimpeded. And besides, a liner is relatively cheap to replace.
If you don’t find a kink in the liner, take your air hose and blow through the liner. If you see debris come out, great. If not, replace the liner. There is still something in there that is restricting your wire travel.
Be careful when you remove the new liner from the package! There are some wire ties that hold it in a loop for packaging purposes. When you are removing these ties, be sure to securely hold the liner ends. If you simply remove the wire ties without holding the ends they can whip around and smack you (or someone else). So be careful!
To install the new liner, carefully start it into the machine end of the gun and gently push the liner through. As it gets close to the actual gun end, you may start to feel some resistance. In this case I just rotate the liner as I’m applying pressure on it towards the gun. Most liners come in a length that is longer than your actual gun. I guess they just decided to make a ‘one length fits all’. Anyway, push the liner until it seats into the machine end, tighten the set screw, and then move to the gun end.
Hold the diffuser removed earlier next to the gun to check how much of the liner will actually get to the set screw once it is cut to length. You need to be mindful of this because if you cut it too short, you’ll be buying another liner. It’s better to cut it too long and trim it afterwards. After cutting off the excess liner, reinstall the diffuser and tighten the set screw (if it had one). Keep in mind that the set screw does NOT need to be cranked down super tight; you’ll distort that shiny new liner if you do so (and yes I have run across this!). Don’t reinstall the contact tip or nozzle at this time.
Reinstall the gun assembly back into your machine in reverse of removal. Thread your wire back into the drive and into the back of the gun assembly. Fasten your tensioner, turn the machine on and press the trigger. Let the wire drive feed the wire through the gun until it pokes out of the diffuser. Install the tip and nozzle. Now let’s recheck the tension.
As stated earlier, you will have an adjuster for the tension on the wire drive assembly. Back it off a couple of turns, then pull the trigger and see if the wire will curl, as we did at the beginning of this article. If not, then tighten the tensioner until it does. Ideally you want to tighten the tensioner until the wire just curls without any hesitation. This practice prolongs the life of your drive motor.
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