Bob Deroeck
02-16-2012, 5:25 PM
I'm in the process of recommissioning a 1974 Powermatic 66 table saw I bought last year. I ran the motor for maybe 5 minutes before I bought the saw. Then it sat in my garage for a year while I built my workshop and ran power and gas lines underground.
In the last week I've done maybe 5-10 rip cuts on the saw while making a mobil base and support legs for the extension table. Today after making a couple of cuts, the motor wouldn't start. It hummed and the fan was oscillating a few degrees on either side of the shutdown position, but it wouldn't kick in. I quickly shut it down. Waited a few minutes and tried again. Same result. There was no smoke or burning smell from the motor. The motor is a 3 HP single phase Baldor, built in 1989. From reading posts from the SMC archives, it seems the likely causes of the problem are either the start capacitor, the centrifugal switch that shuts off the start capacitor after the motor attains a certain RPM, or the start windings.
I disconnected the power cord, put on rubber gloves and removed the cover for the capacitors. There was no oil leakage and no smell from the capacitors. I removed each connector from each capacitor and reconnected them. But, all connections were clean and tight, so I doubt poor connnections were the problem. Anyhow, I put it back together and the motor started right up 3-4 times with no problem.
What do you guys think caused the problem? Can start capacitors operate intermittently? My impression was that when they fail, they fail. Is this correct?
I also suspect that when the start windings fail, they fail. Is this correct?
I'm guessing the problem might have been with the centrifugal switch and that it was stuck in the open position when the motor wouldn't start and that my monkeying around with the capacitors (including tapping the capacitor cover with a rubber mallet to free it from the motor case) might have knocked the centrifugal switch closed allowing the motor to start. Does this make sense?
My current plan is to do nothing further and see if the problem happens again. If it does, I'm thinking of taking the motor apart to check the centrifugal switch, the bearings and inspect the windings and rotor. I've looked at the Baldor parts drawing and everything looks pretty straight forward. Are there any things I should be weary of if taking the motor apart, such as things going "sprong" and whizzing past my ear as I remove the guts from the motor case?
Any suggestions are welcome.
Thanks.
Bob
In the last week I've done maybe 5-10 rip cuts on the saw while making a mobil base and support legs for the extension table. Today after making a couple of cuts, the motor wouldn't start. It hummed and the fan was oscillating a few degrees on either side of the shutdown position, but it wouldn't kick in. I quickly shut it down. Waited a few minutes and tried again. Same result. There was no smoke or burning smell from the motor. The motor is a 3 HP single phase Baldor, built in 1989. From reading posts from the SMC archives, it seems the likely causes of the problem are either the start capacitor, the centrifugal switch that shuts off the start capacitor after the motor attains a certain RPM, or the start windings.
I disconnected the power cord, put on rubber gloves and removed the cover for the capacitors. There was no oil leakage and no smell from the capacitors. I removed each connector from each capacitor and reconnected them. But, all connections were clean and tight, so I doubt poor connnections were the problem. Anyhow, I put it back together and the motor started right up 3-4 times with no problem.
What do you guys think caused the problem? Can start capacitors operate intermittently? My impression was that when they fail, they fail. Is this correct?
I also suspect that when the start windings fail, they fail. Is this correct?
I'm guessing the problem might have been with the centrifugal switch and that it was stuck in the open position when the motor wouldn't start and that my monkeying around with the capacitors (including tapping the capacitor cover with a rubber mallet to free it from the motor case) might have knocked the centrifugal switch closed allowing the motor to start. Does this make sense?
My current plan is to do nothing further and see if the problem happens again. If it does, I'm thinking of taking the motor apart to check the centrifugal switch, the bearings and inspect the windings and rotor. I've looked at the Baldor parts drawing and everything looks pretty straight forward. Are there any things I should be weary of if taking the motor apart, such as things going "sprong" and whizzing past my ear as I remove the guts from the motor case?
Any suggestions are welcome.
Thanks.
Bob