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Brushes arc severly at point of contact with commutator. More than just brushes not seated. Comm. is round clean and looks good. Stator has been changed. Made no differance. Brushes are good.

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If the brushes are long enough, severe arcing is often CAUSED BY FAILURE of one of the windings on the armature, NOT the stator.

Either an open or shorted winding will cause this. Use an ohmeter between adjacent segments to check the resistance. The resistance can vary by say, 10%, but if you find one pair that is outside that a bunch, look for broken wire near the commutator that you might repair, but beyond that, you usually have to replace the armature.

Posted on Sep 04, 2009

Testimonial: "Thank you for input. Shorted armature is what I expected but I never had one act just like this before. Usually the motor won't get up to speed. "

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1 Answer

Fein Multi too FMM350Q. took it apart,checking for null on stator unit, and across the armature unit. What are the best contact points to assess if windings are good?


Greetings - The most common issue with this tool is the controller, next is the stator, then the armature.
https://vserv09.fein.bawue.com/spc/index.php?r=item%2Flist&id=8141
You can use a simple continuity tester to see if the field (stator) is good by checking continuity in each winding.
When the armature goes bad it is usually very obvious with a raised and burnt segment on the commutator - if this is the case you will need to replace the brushes as well.
If the field rings out and the armature looks good I would replace the controller.

Feb 11, 2017 | Fein Saws

2 Answers

When I run my Makita Impact wrench one of my brushes spark what is the problem


One can expect a small amount of arcing from a carbon brush. If one brush is arcing more than another, or if the arcing is following around the diameter of the commutator toward the other brush, the brushes need to be replaced and commutator cleaned with a commutator stone.

Apr 11, 2014 | Makita 6906 9 Amp 34Inch Impact Wrench

1 Answer

Bright sparks while motor is running.


the commutator culd just be dirty. Remove the brushes again and look into the brush tubes while slowly turning/pulling the blade and look for discoloration of the comm bars. If one is raised that is your problem. You can try and SEAT the new brushes before replacing the armature. If you do replace it I would recommend replacing the bearings also. Let me know and I will try and help more.

Jan 19, 2012 | Milwaukee Tool Saws

1 Answer

My 10 yr old son decided to "work " on my mixer ,


Jim, hi- um, you're reading this with your son, right?

Inspect the brushes carefully, be sure that the little copper wire is firmly attached to both the brush and the little disc at the other end of the spring. Clean the brushes well, allow no oil at all to contact them and if they have gotten oil on them (including cooking oil) clean them with a spray can of electric motor cleaner. If you use non-flammable motor cleaner you will have less of a chance of starting a fire, but it's much slower to evaporate. When you put the brushes in, look at the ends and turn the brush so that the hollow worn into the end fits properly to the commutator. The mixer will run with the brushes turned wrong, but it's simply good practice to fit them properly.

Dust and corrosion will accumulate between brushes and their holders, and it's very possible for a brush to not go all the way into position when reinserted. Again, the electric motor cleaner will help- spray a bit down the hole and on the brush, slide the brush in and out and note any stickiness as it reaches the bottom of the hole. Each brush must contact the commutator with the full pressure of the spring behind it and be free to move as the machine is used and the brushes erode. Note that cleaning the holders can take several tries, and if there is crud in the holder the condition will get worse before it gets better, so take note of how the brush moves, especially at the bottom of its travel. When it's clean you'll be able to hear it contact the commutator when you put it down the brush holder.

If you look down the brush hole you'll see the commutator- the copper bars of the commutator should have a pretty, burnished appearance and the insulation between them should be clean and not standing up above the bars. Black sooty looking deposits and/or pitting indicate that the brushed have not been advancing to the commutator with wear as they should, and arcing has been taking place. This will be caused by dirty brushes binding in their holders or by worn out brushes that are unable to advance or by the commutator bars wearing faster than the insulation between them- a condition referred to as "high mica".

Good luck, and buy that kid some tools- there's a lot more to discover inside that mixer..

lp

Dec 22, 2010 | KitchenAid Food Mixers

1 Answer

Carbon brushes burn out too fast


you possibly have an armature problem causing them to arc and burn fast. look at the commutator for unusual discoloration and raised comm bars.

May 16, 2010 | Bosch Brute Breaker Hammer 11304

1 Answer

I have a dewalt angle grinder 4'' that carbon are sparking and stator suddenly hot whats the problem


could be worn brushes a shorted armature or field issue. check the brushes first and the commutator would need to be cleaned to seat the new ones. that is the cheapest route.

Mar 15, 2010 | Dewalt Saws

2 Answers

Needs rebuilding, brushes arcing, loss of power,etc.


Pull the brushes out and sand them off lightly with a fine grade sandpaper. Then push a small piece down in the brush holder and hold it against the commutator while you turn the blade to clean the comm. It' s as good as new!

Nov 06, 2009 | Bosch 4000 - 07 Electric Table Saws

1 Answer

Just replaced the brushes on a WE14 150 Quick 6 Grinder and sparks now come from the brushes


From my own experience.

Are the strips of the commutator smooth and flat?
(Not to insult you. The part of the armature that the brushes ride on)

If they aren't, the brushes will bounce up and down.
I put one end of the armature in a drill, and have a helper run the drill. The other end of the armature rests in the front bearing of the grinder head, which is fastened down. (To a bench) Then I use a medium tooth, (B astard) file to dress the commutator bars flat.

I also put medium grade sandpaper in-between the brushes, and the commutator surface to dress an arc on the brushes. (Turn the armature by hand while keeping the sandpaper in place)
Brushes come with a flat surface. Putting a radius on them to fit the arc of the commutator, gives them a good contact surface to start from.

Be sure the springs are putting pressure on the brushes. Sometimes the brush mounts need to be cleaned, or the brush will not slide through the mount like it should. The brush will again, 'Dance' on the commutator. (Bounce up and down)

Sep 06, 2009 | Metabo WE14-150 Quick Angle Grinder

4 Answers

"CHANGING CARBON BRUSHES ON A DYSON VAC"


Solent Tools have a full range of Dyson brushes available. Tel 023 8057 8057. www.solenttools.co.uk

May 25, 2009 | Dyson DC07 Animal Bagless Upright Cyclonic...

1 Answer

Craftsman 10" table saw losing power


Depending on how much "arcing" you see it could be a couple different items. First some arcing is normal and usually runs across the brush edge, but if it is a lot and goes around the armature then it could be a brush spring that collapsed or worse the armature has an open or damaged segment on the commutator, I would take the brushes out first and look at them (unplug tool first) the edge that rides on the comm should both look the same and the spring also. If you can see then turn the blade by hand and look at the comm thru the brush tube for a different looking bar on it. Let me know the model number and I will pull up a breakdown and see if I can help you further.

Jan 26, 2009 | Craftsman Saws

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