Question about Dewalt Chop Saw D28700

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My Dewalt chopsaw is loosing power and sparks heavy in brushes

I took the whole thing apart and blew it all out w, high air pressure air then with 600 grit sand paper I clean up the armature and then the actual brushes them selves. It seemed to of helped but I think that maybe moisture in the brushes could be the problem but not sure.

What could be the problem or what is the problem?

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I worked at a tool rental center while attending college and learned to repair tools such as yours. Damage to the armature occurs mostly during low power situations or overloading the motor. The damage is usually visable. Notice burned looking copper windings or commutator bars. You can test with growler or meter. We would turn the commutator on an armature lathe to true the surface of the bars. If the commutator is not perfectly round the brushes will bounce thus cause the sparking that you see. Also you must clean the groves between the bars with a blade to clean out all metal filings that can cause short between bars. (Broken hacksaw blade ground to fit the groves will work fine)Sanding with sandpaper may not be perfect enough to stop sparking assuming the armature is not shorted. Moisture will not effect the brushes, and sanding them square is ok but you can put the curve back by cutting fine sandpaper into strip and wraping it around commutator and insert brush into holder against sandpaper. Not necessary thou because all new brushes are square. New brushes however will increase the tension of the brush against the commutator preventing bounce due to new spring and longer carbon. Good luck enjoy

Posted on Dec 18, 2008

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  • Master
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If it sparking heavily usually that indicates a brush or armature problem. I think after looking at the armature windings for cuts in the wire that I would replace the brushes. Sanding them takes the curve out and they can't seat on the commutator properly.

Posted on Dec 16, 2008

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Dewalt chop saw blows breaker after a few minutes of use. Bearings bushes and armature ae good. Is the gear box dragging so much that it powers off and blows the circuit breaker? Where in San Antonio, Texas can I have it fixed or where can I locate parts to it? Thanks, Romeo

Posted on Jul 28, 2009

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