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Just bought a used 3hp, 230V (Marathon) Unisaw, '97 model in great condition. It ran just fine before I moved it. Unfortunately, the straps broke during the move and it tipped over. It didn't seem to have any significant damage but once I got it home and hooked up, it wouldn't run - not even a hum out of the motor. I checked the power source - all good - 119+ volts on each leg - and the switch and everything seemed good, but still nothing. Finally I hooked the motor up directly to the power source and still nothing. There was quite a lot of dust that blew around during the move so I used compressed air to blow out the parts of the motor I could get to without opening the case. No help. I then decided it must be the run capacitor or worse so I took the saw out of the cabinet so I could work on it more easily. The run capacitor appears to be okay. I checked it by putting my ohmmeter across the terminals to discharge it, then measured DC volts and got a reading that would slowly decrease. From what I've read in the web, that indicates that it's working. Told this story to a guy in a local motor shop and he said to check the continuity of the capacitor wires. I did (although I don't have great faith that I really understand which setting I should use within the continuity section) and it appears there IS NO continuity - by that I mean the meter gives a positive reading, not a zero. What now? Do I have to crack the case to trace the capacitor wires to see if there is, in fact, a loose connection? I can't find my gear puller so getting the pulley off may be a problem. I should probably take it to a pro (and probably will) but the nearest shop is an hour drive each way so I thought I'd see if anyone out there has any other thoughts first. Thanks in advance!!
 

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I would take it to a motor repair facility.









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Disconnect the capacitor from the motor. Discharge the capacitor by shorting the terminals. Place an ohm meter on the two terminals and you should have a complete circuit followed by an open circuit as the batteries in the ohm meter charge the capacitor. This happens quickly and is easier to see with an analog ohm meter. If you don't get a reading of a complete circuit at first you have an open capacitor which is bad. If it continues to show a complete circuit it is shorted and bad.
Tom
 

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please provide your motor info - frame number. is there one cap or two, how many microfarads? it may be a run or a start cap. you shouldn't have to crack it open to check the connections, all wires usually come out in the wire box (start windings, run windings, caps) and are connected there.

sounds like your cap test was successful. start checking the connections inside the wiring terminal box, you may have a drawing to go by on the motor.

problem sounds connection related.
 

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I just conferred with a knowledgeable electrical person and he suggested QUOTE: 119v on each leg doesn't necessarily mean 240v. He needs to see 240v on his meter. Sounds like one leg tripped a breaker or blew a fuse.
 

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I just conferred with a knowledgeable electrical person and he suggested QUOTE: 119v on each leg doesn't necessarily mean 240v. He needs to see 240v on his meter. Sounds like one leg tripped a breaker or blew a fuse.
that is correct, you need to read 240 volts from leg to leg.
nice point.
 

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If you aren't getting a hum out of the motor that indicates that you are not getting power to the motor. Did you get a hum when you hooked power directly to the motor? Can you post a wiring diagram showing how you hooked power to the motor? Also, how did you check the switch? That saw should have a magnetic starter.
Tom
 

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It's reasonable to me to have 119V on each leg. Voltage will vary from house to house. I've gotten anywhere from 110V on a leg to 129V. If there is 238V going to the motor it should run. It has to be the capacitors, internal start switch or the windings.
 

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Steve Neul said:
It's reasonable to me to have 119V on each leg. Voltage will vary from house to house. I've gotten anywhere from 110V on a leg to 129V. If there is 238V going to the motor it should run. It has to be the capacitors, internal start switch or the windings.
Depends where he got the voltage readings. Did he get them out of the wall outlet, before the switch or at the motor? I don't have a clue where he got the readings. I can't rule out the capacitor but I would not even consider it with the info he has given. Need more info.
Tom
 

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Depends where he got the voltage readings. Did he get them out of the wall outlet, before the switch or at the motor? I don't have a clue where he got the readings. I can't rule out the capacitor but I would not even consider it with the info he has given. Need more info.
Tom
In his initial post he tried the saw as originally wired and when that didn't work bypassed the switch and wired the motor directly to the power source with the same results.
 

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Steve Neul said:
In his initial post he tried the saw as originally wired and when that didn't work bypassed the switch and wired the motor directly to the power source with the same results.
That the reason I asked in a previous post to show a wiring diagram of how he wired directly to the motor. He sounded like he was unsure of what he was doing and just wanted to make sure it looked like he did bypass switch correctly. Not really disagreeing with what you said other than I would not rule out a lose wire bad switch etc.
Tom
 

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That the reason I asked in a previous post to show a wiring diagram of how he wired directly to the motor. He sounded like he was unsure of what he was doing and just wanted to make sure it looked like he did bypass switch correctly. Not really disagreeing with what you said other than I would not rule out a lose wire bad switch etc.
Tom
I see your point. Perhaps he missed the ground.
 

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Discussion Starter #14
Problem Solved!!!

First, thank you all for your prompt and helpful responses. It's nice to know there are folks out there who will help when help is needed. Turns out the problem was the power source. 120v on each leg does not necessarily mean 240v. A great lesson for me. I used a 2 pole breaker that only drew off of one bus bar contact rather than a 2 pole breaker that draws off of two contacts on the bus bar. Okay, I'm an idiot and admit it. At least I figured it out before I spent a lot of money to have someone else tell me I'm an idiot. Anyway, saw is purring. Thanks again to all who chimed in.
 

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Swiftowl said:
First, thank you all for your prompt and helpful responses. It's nice to know there are folks out there who will help when help is needed. Turns out the problem was the power source. 120v on each leg does not necessarily mean 240v. A great lesson for me. I used a 2 pole breaker that only drew off of one bus bar contact rather than a 2 pole breaker that draws off of two contacts on the bus bar. Okay, I'm an idiot and admit it. At least I figured it out before I spent a lot of money to have someone else tell me I'm an idiot. Anyway, saw is purring. Thanks again to all who chimed in.
Thanks for letting us know the problem. We have a lot of cases where a new person posts a problem like this and never comes back to let's us know the real problem was after several people have provided advice. I total understand your problem now. Also, welcome aboard.
Tom
 

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First, thank you all for your prompt and helpful responses. It's nice to know there are folks out there who will help when help is needed. Turns out the problem was the power source. 120v on each leg does not necessarily mean 240v. A great lesson for me. I used a 2 pole breaker that only drew off of one bus bar contact rather than a 2 pole breaker that draws off of two contacts on the bus bar. Okay, I'm an idiot and admit it. At least I figured it out before I spent a lot of money to have someone else tell me I'm an idiot. Anyway, saw is purring. Thanks again to all who chimed in.
Yea that would do it. Alternating current runs from + to - and without the other line the power would be just turning on and off. It needs the opposite line for the neutral.
 
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