Northern Industrial recipricating saw only hums-

8 years 3 months ago #1425 by ba_50
Hi,

This saw is just like new and only hums. Can I fix it? Model #143381 Thanks

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8 years 3 months ago #1426 by MTR-Admin
Replied by MTR-Admin on topic Northern Industrial recipricating saw only hums-
Thanks for the post!

A couple of things come to mind...

1. Loose wires connected to the switch or motor.

2. Brushes are worn down or are not touching the commutator on the armature (check to make sure the brush springs are in good shape, which put tension on the armature).

3. Make sure you have continuity throughout the tool. I would take a voltage meter and connect it to the power cord to confirm you're getting a good current.

You can watch a video on how to do just this below:



4. Make sure the armature gear and planetary gears aren't stuck/damaged. To confirm this you'd have to remove the gear cover, of course; I would check this last.

Hopefully this gives you a good starting point.

- MTR

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8 years 3 months ago #1428 by ba_50
MTR
Well I used an ohm meter to check the switch and believe it is ok and tightened the connections. It still hummed at a low power setting yet when turned up high there was a big flash of light at the armature and smell of smoke. Turned it back down and it hummed again. The brushes looked ok.

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8 years 3 months ago #1429 by MTR-Admin
Replied by MTR-Admin on topic Northern Industrial recipricating saw only hums-
I think there may be a section of the commutator (which the brushes make contact with) that's damaged/burnt or missing completely, causing this problem.

Check to confirm all of the copper sections of the armature's commutator are there; you may need to "dress" the armature to clean it up, and you can buy a product to do this at a hardware store, typically.

Make sure the field and armature windings/wires aren't burnt or missing as well.

- MTR

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8 years 3 months ago #1430 by ba_50
The commutator looks great. My brother bought the saw new and didn't use it much. Warranty was out.

The windings looks normal and shows no indication of burning. The commutator starts to move, stops, and starts sparking.

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8 years 3 months ago #1435 by MTR-Admin
Replied by MTR-Admin on topic Northern Industrial recipricating saw only hums-
It's hard to say, then, without having it to diagnose myself.

The problem with this is going to be obtaining parts; I doubt they're available through Northern Tool as it's probably an import saw private labeled.

The gears could be jammed, you may want to remove the gear case and take a look. If all of the electrical components look okay and the armature and brushes do as well, I'd look at the gears.

- MTR

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