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220 Volt, Table Saw Switch Question

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Forum topic by BTKS posted 09-05-2010 03:58 AM 3335 views 0 times favorited 6 replies Add to Favorites Watch
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BTKS

1984 posts in 2931 days


09-05-2010 03:58 AM

Topic tags/keywords: question

All,
I am wondering about my table saw switch. It was making a humming or buzzing noise today when the saw was turned off. The sound reminded me of an electric motor that won’t start, just locks up and buzzes. I pulled the plug and the noise stopped. It was real faint, I only heard it when everything in the shop was shut off and no background noise. The thermal breaker did not trip and there were no abnormal functions.
Hope someone knows if my switch is about to go kaput or if it might be normal.
Thanks, BTKS

-- "Man's ingenuity has outrun his intelligence" (Joseph Wood Krutch)


6 replies so far

View snowdog's profile

snowdog

1158 posts in 3449 days


#1 posted 09-05-2010 02:05 PM

I am no electrician but sure do tinker.
Sounds like a short. If you took the switch apart and do not see anything wrong (wires, dust, moisture) I would consider changing (replacing) the switch. Is the polarity correct?

-- "so much to learn and so little time"..

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lew

11347 posts in 3222 days


#2 posted 09-05-2010 03:52 PM

The switch is probably a “magnetic starter” type. There are electromagnets in it that may be vibrating. This could occur if their mounting screws get loose. You could pull the plug, open the the starter and tighten any MOUNTING hardware. There are ADJUSTMENT screws that should NOT be turned!

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View MedicKen's profile

MedicKen

1610 posts in 2929 days


#3 posted 09-05-2010 04:21 PM

I agree with Lew that it most likely is a magnetic starter. I would check to see that all of the wiring connections are tight as well as the mountings. A loose connection can cause the noise as well as a fire hazard. Magnetic staters also have a set of contacts that over time can become pitted and corroded. take a look at the contacts and see if they are burnt, they can be cleaned up with some disassembly and filing/sanding. If you dont feel comfortable in disassembling and or cleaning the contacts call a qualified electrician. Here is a short article on cleaning the contacts.

-- My job is to give my kids things to discuss with their therapist....medic20447@gmail.com

View BTKS's profile

BTKS

1984 posts in 2931 days


#4 posted 09-05-2010 05:53 PM

Thanks all,
The switch is a magnetic starter. Power is interrupted to the saw, the switch defaults to the off position. I’ll give it a try. Either way the worst case scenario is replacing the switch.
MedicKen, Thanks for the link, going there now.
BTKS

-- "Man's ingenuity has outrun his intelligence" (Joseph Wood Krutch)

View lew's profile

lew

11347 posts in 3222 days


#5 posted 09-06-2010 12:27 AM

Grizzly has some pretty reasonable replacement magnetic starters.

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View EEngineer's profile

EEngineer

1061 posts in 3080 days


#6 posted 09-06-2010 02:50 AM

It could indeed be a magnetic starter. I looked at a few of these to determine how they work. The Delta unit I looked at, to give flexibility with a wide range of voltages, used a step-down transformer to energize the contactor. Rather than changing the contactor coil for different motor voltages, you just moved a tap on the transformer to adjust the motor voltage down to 24 VAC (IIRC) to drive the contactor coil.

The transformer is always driven even if the motor and contactor are not. If the laminations on the transformer are loose then it will buzz. It doesn’t necessarily indicate a faulty transformer or anything dangerous.

-- "Find out what you cannot do and then go do it!"

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