Need help troubleshooting old Black And Decker Circular Saw

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  #1  
Old 11-21-05, 12:34 PM
ROcHE
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Need help troubleshooting old Black And Decker Circular Saw

Hi,

My father has an old Black & Decker Circular Saw (~30 years old). He loves it but it's not working right anymore. Blue fire comes out of the motor and the whole unit becomes very hot and is not powerful.

I have replaced the brushes but it is still the same. I've heard that the motor might be failing. There is two part (the armature and the electromagnet (or coil??).

How does one test an electric motor? The armature is rather costly (100$ ) and I'd like to test it before buying a new one.

Thanks for any inputs!
 
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  #2  
Old 11-21-05, 04:18 PM
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The commutator is what the brushes make contact to on the armature.
The wires get loose that connect to the commutators copper segments.
as the wires get looser you will start seeing flames that follow the circumference of the commutator.

The centrifugal force pulls the wires loose, I have tried to repair some without any good results.

If you were to measure the resistance from one copper segment to the next one, all your readings will be the same on a good armature.

You need a new armature.
But if you over heated the field/coil that's not good.
 
  #3  
Old 11-21-05, 04:34 PM
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why would you evan think about putting 100 in a 30 year old saw ?
 
  #4  
Old 11-21-05, 05:47 PM
ROcHE
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So basically it's the armature for sure? Is it possible to test the coil?

Droping 100 on a 30 years old saw is crazy. That's why I want to make sure it is not an easy fix. My father already bought a new one but he says he prefers the old one
 
  #5  
Old 11-21-05, 07:33 PM
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" So basically it's the armature for sure? "
97% yes its bad.

In my first post, you can use an ohm meter and check the resistance if you have any doubt.

"Is it possible to test the coil? "
Yes.

Most people don't have the equipment to properly test the coil 100%
You can test the resistance, but knowing that the saw turns that test is not going to tell you anything.

The best you can do, look at the color of the varnish on the coil, if it looks burnt that's not good.
if the varnish flakes off the coil, its not going to last.

The varnish is the insulation for the copper wire.
If its a shiny uniform color, then its more then likely good.
 
  #6  
Old 11-21-05, 07:48 PM
ROcHE
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Thank you for your help.

I will look into that.
 
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