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Old 09-26-2011, 08:17 PM   #1
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Miter Saw Tripping Breaker


Hello to the group. I found a Dewalt DW705 Compound Miter Saw on a curb. It was missing the brushes and brush caps. I ordered a new set taking a chance and when I put the brushes in, it will run but then trip a breaker. I can run it for 30 seconds max before the breaker trips.

I know you're supposed to run the motor to "break in" the brushes so the conform to the commutator. I should also mention there is no blade for this saw, I didn't want to sink more money into it.

Could it be the armature may need replacing or would the brushes not being worn in yet be pulling more current. Also I'm wondering if there is no blade that the motor may not be running correctly without the blade acting as a flywheel.

If the armature is bad, it may wind up back on the curb. For as much as I would use it, I can buy a new cheapie at Harbor Freight.

Any comments would be welcome and thanks,

Brian

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Old 10-04-2011, 07:12 PM   #2
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Miter Saw Tripping Breaker


take it to a service center to get looked over.

another thought is how new is the electrical in the house. the most recent codes for electrical call for afci outlets.. these will trip if they have a large draw through them, mainly required in bedrooms and living areas which will only ever have low voltage devices plugged into them. large items like saws will trip them everytime, ran into this problem on a house a couple years ago

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Old 10-04-2011, 08:06 PM   #3
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Miter Saw Tripping Breaker


Thanks for the reply. I was trying it through an extension cord, so that may be adding more current draw to the breaker. I'll try it directly to an outlet. The outlet I was using wasn't gfi, nor the breaker. Hopefully that'll take care of me. If not, I may just buy a harbor freight cheapie. I would use the saw maybe once or twice a year if I'm lucky.
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Old 10-04-2011, 10:08 PM   #4
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Miter Saw Tripping Breaker


Put it back on the curb. It was there for a reason. Once or twice a year usage is perfect for Harbor Freight tools.
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Old 10-05-2011, 06:45 AM   #5
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Miter Saw Tripping Breaker


Those have a history of failed shaft bearings on the blade side----spin the motor with your fingers and see if the bearing is shot.
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Old 10-05-2011, 06:49 AM   #6
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Miter Saw Tripping Breaker


Quote:
Originally Posted by Missouri Bound View Post
Put it back on the curb. It was there for a reason. Once or twice a year usage is perfect for Harbor Freight tools.
I disagree, there are only so many things that can go wrong, worst case being the armature.

I just replaced the armature and bearings on my 708, it cost $94. That’s a small price to have a good tool working again. More value for the buck than you’ll ever find at HF.
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Old 10-05-2011, 07:02 AM   #7
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I had one of those (bearings shot) --Nice light saw--Plenty of instructions available for repairing it.
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Old 10-05-2011, 08:44 AM   #8
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Miter Saw Tripping Breaker


The motor spins freely enough. Now that the weathers a bit cooler I can work on it some more. If the bearings are getting bad, I can do that no problem. If it's the armature, those cost around $100. Not sure if I want to spend that much. We'll see.

I found a nice Hitachi Table Saw, and a Husky Air Compressor in the same pile with the DeWalt, and the table saw works great. The rip fence is missing, but I have materials to make another one and it could use a new blade. The commutator on the compressor was really messed up (pitted), so that went back out.
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Old 10-05-2011, 09:04 AM   #9
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Miter Saw Tripping Breaker


As long as you're in there, I would take a look at the switch too. I haven't had to replace any for a while, but thinking back, I have probably replaced as many trigger type switches as brushes, not necessarily on miter saws, but electric tools in general.

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