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Multimeter help to test for table saw voltage

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Forum topic by ColonelTravis posted 06-23-2014 07:00 PM 1491 views 0 times favorited 31 replies Add to Favorites Watch
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ColonelTravis

1188 posts in 1353 days


06-23-2014 07:00 PM

Topic tags/keywords: sawstop multimeter voltage table saw

SawStop not working, motor doesn’t spin at all. Talked with customer service for a while. I can manually override the switch box and turn the saw on by pressing down on those two little rectangles in the middle there of my pic below. (SS guy talked me through this, I didn’t do it on my own.)

However, when I press those little things down the saw starts off slow, which could mean I need to replace a capacitor, which they are overnighting. But going through some other stuff on the phone, it could also be a bad switch box entirely, so he’s sending one of those along, too. Will have to wait and see tomorrow.

In the meantime, I wanted to check the voltage coming to the saw. It’s hooked up to a 20-foot 10 gauge extension cord. Obviously there’s current going to the saw, but could it be a cord problem? Got a multiimeter not too long ago, and I also want to know this for future reference. If you want to learn how to test a battery and outlet there are videos and sites out the yin-yang to test a battery and outlet – I can do that in my sleep. But testing live wires like this? I can’t find anything, totally ridiculous. Where do the multimeter leads go to check for voltage? This is the current (maybe, defective) switch box:

Bottom wires are going back to the saw, so would I put the black MM lead on the top black screw, red MM lead on the top white, and/or test top and bottom, and/or something else?

For the record, I’m not sticking leads into wires and outlets for the heck of it, etc. All I want to know for now is this.


31 replies so far

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Richard H

489 posts in 1140 days


#1 posted 06-23-2014 07:12 PM

What the HP of the motor?

That’s pretty good support to be overnighting you both a new capacitor and switch box.

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ColonelTravis

1188 posts in 1353 days


#2 posted 06-23-2014 07:38 PM

3 HP.

Yeah they were good to talk to, apologetic, helpful, etc. I’ve heard similar stories about how good their CS is and so far I agree.

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HerbC

1592 posts in 2319 days


#3 posted 06-23-2014 07:54 PM

Yes, to check the incoming voltage, with saw switch in the off position, put meter in AC Voltage scale, with the scale that includes the expected maximum voltage, put black lead on terminal (L1) which has the incoming black insulated wire and the red lead on the terminal (L2) which has the incoming white insulated wire.

Be careful!

Herb

-- Herb, Florida - Here's why I close most messages with "Be Careful!" http://lumberjocks.com/HerbC/blog/17090

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ColonelTravis

1188 posts in 1353 days


#4 posted 06-23-2014 09:16 PM

Thanks Herb. I got 122V from a 220 outlet. Should it not be the full 220?

View Fred Hargis's profile

Fred Hargis

3926 posts in 1953 days


#5 posted 06-23-2014 09:25 PM

It should actually be almost 240V. Re check you have the scale on the multimeter set correctly, and the leads in the right spot and re check. If you still read low voltage, test the outlet you are using and make sure you have 240V there (same procedure, one lead to each hot leg, on your outlet that would be the 2 flat openings.

-- Our village hasn't lost it's idiot, he was elected to congress.

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Richard H

489 posts in 1140 days


#6 posted 06-23-2014 09:34 PM

If your getting 120V are you sure the Extension code and wall outlet are wired right? You have three wires. 120V to Neutral, 120V out of phase to Neutral which creates a 220V difference between the L1 and L2 terminals. If the Neutral and one of the 120 leads got reversed it would cause you to only read 120V difference and have a hot Neutral which would measure 120V to one of the L terminals and 220V to the other.

Have you tried plugging the saw directly into the wall?

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ColonelTravis

1188 posts in 1353 days


#7 posted 06-23-2014 09:42 PM

Sorry, meant 240. Yeah, outlet is fine. Just tested the extension cord and it also read about 120. I didn’t think I wired it wrong but is that the culprit?

Can’t plug the saw directly into the wall, it’s a complicated story but I have to use the dryer outlet for now.

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Redoak49

1936 posts in 1448 days


#8 posted 06-23-2014 09:44 PM

Is this a new SawStop? Has it every worked correctly?

Have you used any other 220 volt tools with the extension cord?

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William Shelley

149 posts in 929 days


#9 posted 06-23-2014 09:48 PM

This is a pet peeve of mine so please forgive me…

220V DOES NOT EXIST

In the USA, the residential single-phase electrical grid is 120V or 240V ONLY.

With that being said, a double pole (240V) branch circuit does not necessarily require a neutral. It is entirely acceptable to have a 3-wire 240V circuit where L1 and L2 are both hot, and no neutral is present, just a ground. There will be a 240V difference between the two legs and typically a 120V difference from either leg to ground.

You’ll need to probe the receptacle the saw plugs into and ensure it’s at the correct voltage.

-- Woodworking from an engineer's perspective

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Richard H

489 posts in 1140 days


#10 posted 06-23-2014 09:50 PM

120V between what terminals? Maybe a picture of the end of the extension cord you plug the saw into with voltage measurements between terminals would help.

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ColonelTravis

1188 posts in 1353 days


#11 posted 06-23-2014 09:55 PM

The saw is brand new, never been turned on until this past weekend.
Extension cord plug that goes to the saw (this is where I got the 120ishV reading, like the saw terminals):

Plug that goes to the dryer outlet (two pics because it’s so big)

View Shawn Masterson's profile

Shawn Masterson

1297 posts in 1408 days


#12 posted 06-23-2014 10:02 PM

Green is ground, white and black are both hot. If you probe the green wire and the black or white wire there should be 120 volts. If you probe the black and white wire then you should read 240 volts, give or take.

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ColonelTravis

1188 posts in 1353 days


#13 posted 06-23-2014 10:07 PM

The black and white wires of the plug that connects to the saw (Photo 1 above) was the 120~ reading.

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Richard H

489 posts in 1140 days


#14 posted 06-23-2014 10:07 PM

What Shawn said but please be careful as some of those wires look exposed. You might want to test from the front terminals instead of the back wires to make sure they make contact though.

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Richard H

489 posts in 1140 days


#15 posted 06-23-2014 10:08 PM



The black and white wires of the plug that connects to the saw was the 120~ reading.

- ColonelTravis

What do you see Black to green and white to green?

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