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Folks,
Looking for some help trying to diagnose/repair.
Sometimes when I release the switch the saw brakes to a stop. Other times it needs to spin down and then the brake kicks on.
I am not sure how this safety brake works. I have a parts diagram and I see no obvious part that serves as a brake.
Is it done electrically?
any help?
Mark
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I have the same issue with my Bosch 12" box. Good question. I've been blowing out the switch with air, sometimes that helps but its not fixed the problem. Interested in the responses.
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This is interesting. My older DeWalt 715 has been intermittent nearly from day 1. In fact I feel like my brake issue has actually decreased over the years, which is weird. Nevertheless, it would be helpful to know if there's any sort of fix. This saw has been an amazing performer by the way - thousands and thousands of cuts and has held its settings. One of my best woodworking buys.
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Most miter saws use dynamic braking where the motor becomes a generator when voltage is not applied. Easiest thing to check are the brushes, make sure they are free and not worn out. A dirty commutator could also be a issue or the switch itself that applies a short or load when it is shut off. I know it is counter intuitive for the brushes to be the problem but check them first. Roly
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11-01-2018, 03:53 PM
(This post was last modified: 11-01-2018, 05:49 PM by Stwood_.)
(11-01-2018, 03:08 PM)Info on the I nternet Wrote: The DW 705 and 708 (most all Dewalts) use an electrical brake to stop the motor. This is usually another winding in the motor that is connected to the primary motor windings when the switch is released. The primary motor becomes a generator because of the collapsing magnetic field in the primary windings. The electrical energy goes through the switch (and brushes) to the brake winding to slow or stop the motor. I'd inspect the brushes, and replace them if they are worn. If not, then I'd replace the switch since it controls the starting and stopping. If that fails to correct the problem, the only items left in the brake system are the field and armature.
I've removed the handle covers and blew the surrounding dust out of the switch and that has cured 2 of my Dewalts. I also checked the wire connections while there. So not really sure what fixed them, but the brakes started working again.
Steve
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WaterlooMark 02/9/2020
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(11-01-2018, 03:08 PM)Roly Wrote: Most miter saws use dynamic braking where the motor becomes a generator when voltage is not applied. Easiest thing to check are the brushes, make sure they are free and not worn out. A dirty commutator could also be a issue or the switch itself that applies a short or load when it is shut off. I know it is counter intuitive for the brushes to be the problem but check them first. Roly
Roly,
"Dynamic Braking" who knew. When I did a search I found a ton of info. Not knowing what to call it was the problem. That is why having human beings to talk to will never go out of style.
I may try checking the brushes. Easiest first.
I'll circle back with results.
Thanks
Mark
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(11-01-2018, 04:51 PM)sawnuts Wrote: Roly,
"Dynamic Braking" who knew. When I did a search I found a ton of info. Not knowing what to call it was the problem. That is why having human beings to talk to will never go out of style.
I may try checking the brushes. Easiest first.
I'll circle back with results.
Thanks
Mark
Well that was easy.
I pulled the brushes and they had a lot of life left but they were a little crusted up on the business end. I cleaned them (sand-paper) and got to some better material.
It fired right up and I tested it maybe 5 times. Every time it acted the same. It took maybe 5 seconds to stop spinning but it is consistent. Before it was very inconsistent.
Thanks tons,
Mark
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(11-01-2018, 05:25 PM)sawnuts Wrote: Well that was easy.
I pulled the brushes and they had a lot of life left but they were a little crusted up on the business end. I cleaned them (sand-paper) and got to some better material.
It fired right up and I tested it maybe 5 times. Every time it acted the same. It took maybe 5 seconds to stop spinning but it is consistent. Before it was very inconsistent.
Thanks tons,
Mark
Well, that's what I gotta do. Thanks to all.
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(11-01-2018, 06:17 PM)Admiral Wrote: Well, that's what I gotta do. Thanks to all.
+1
I've had similar issues with my DeWalt. Good info!
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