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Rusty

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I have an electric motor on a 1958 Craftsman band saw that just hums. I assume it is a capacitor. Do I have to split the motor case to replace it?
 

Jeff Handy

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Pictures would help.

Also picture of the info plate, showing model, serial number, amps, etc.

Don’t assume you already know why it won’t run, that limits the feedback and helpful hints you will get.

Maybe the brushes are bad?
 

JoeD

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The capacitor will be on the outside.
A more likely cause of your problem is a stuck start switch.
 

kok328

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The capacitor will be on the outside.
A more likely cause of your problem is a stuck start switch.
I would think this motor would be capacitor start, which would not have a start winding like a shaded pole motor. The capacitor will be mounted on the motor and readily accessible to test and/or replace.
 

pjones

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You probably have a PSC or a CSCR motor.

PSC (Permanent Split Capacitor) motors often have the replaceable cap under a bulge like cover attached to the outside of the motor.

CSCR (Capacitor Start Capacitor Run) motors will have two of those bulges. One for the run cap and one for the start cap. When the motor is stopped the internal centrifugal switch should be closed so the start cap is in circuit. If it is stuck in the open position and if the capacitor does not have a bleed resistor on it then the capacitor may remain charged and is a SHOCK HAZARD. I’m making that bold because it is a safety issue to be aware of. You can use an ohm meter to check for continuity once the capacitors are discharged and removed, to check the switch and windings.

If your motor has an open winging this can allow one or both capacitors to remain charged and present a SHOCK HAZARD.

Capacitors fail often. They are replaceable for a reason. Just be careful when you do it to discharge the capacitor first and replace it with like for like.

I suspect with a motor that old you have worn bushings. Usually not worth fixing for a small band saw type motor. End to end play is normal for bushing type motors (ball beating motors do not have end to end play), but side to side play is the killer. Disconnect the drive from the shaft and give it a firm push and pull in all directions. If you feel nothing that’s good. If you feel a tiny click click then your bushings are worn and your rotor is probably contacting your stator when the magnetic field energies, Time for a new motor.

Your bushings May also have dried up. Those motors typically have oil ports for servicing. If they’ve gone dry and this is your telling sign then the damage is already done and you will waste your time trying to fix it (ask me how I know)... so many unsuccessful attempts...

While your drive is off, grip the shaft and pull while spinning it. Is it smooth? If not then you have bearing damage or debris lodged causing a restriction. Fix or replace based on your findings.

Good luck, be safe.
 

pjones

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I should add, some motors do not use capacitors and instead the start switch disconnects the start winding once it gets up to speed. Induction start Induction Run, they don’t have a capacitor on them at all. If that more closely resembles your motor then the motor is most likely done and will require replacement if the start switch is not stuck in the open position.

I can’t think of any motors off the top of my head that have capacitors built into them that require the removal of the end plates to access them. Not only is there just physically not enough room for a capacitor inside the motor to store a capacitor, but a capacitor hates heat and being installed inside the motor would result in reduced thermal transfer to the ambient air and cause them to fail faster (plus it would not be serviceable then).

Based my speculations I am guessing your motor does not have a capacitor. A picture would help confirm the information that is being assumed and eliminate any doubt.
 

Rusty

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Sorry, I have been too busy to get out into the shop. It does not have a bump on it, so from what you posted I assume no capacitor. The only inspection plate is a small one that shows the electric connections.
 

68bucks

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Have you tried oiling the bushings? I have a 1959 craftsman table saw and had that problem. Mine has a capacitor though. I oiled the bushings and worked the motor by hand, did that a few days and that took care of the problem. I did replace the capacitor first thinking that was the problem but that didn't initially fix it. My motor had felt packing to hold the oil.
 

Rusty

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Have you tried oiling the bushings? I have a 1959 craftsman table saw and had that problem. Mine has a capacitor though. I oiled the bushings and worked the motor by hand, did that a few days and that took care of the problem. I did replace the capacitor first thinking that was the problem but that didn't initially fix it. My motor had felt packing to hold the oil.
I will try that. I have been so busy after I posted I haven't had a chance to get back to it. It ran once after I bought it and has just hummed since. I don't really need this saw bought it as a backup. I have a modern 14" Craftsman and a 12" Grizzly. I just hate to have anything that doesn't work. (reminds me of one of my kids)
 

pjones

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Is it wired up for the correct voltage? Sometimes the motors have a dual voltage rating but you need to connect the wires differently depending on what voltage you are supplying to it.

Sounds like your motor simply doesn’t have a capacitor, or there are two brown wires that extend from the motor that get connected to a capacitor. If those got capped or cut then that could be the problem.

You could also check the start switch inside the motor. Honestly though it’s not a common problem to have them stick open so it’s unlikely. Doesn’t mean it can’t or won’t happen though.

Sounds like the saw is old but the motor is new and recently replaced? Could you post the specs of the motor that you see on the nameplate?

I have a hard time following this forum ever since they stopped supporting tapatalk so unfortunately it’s hard and for me to keep up with topics on the go. I’ll do my best to check back in a timely manor while you work on this motor.

If you remove the belts and hand spin the motor what does it sound like and feel like? If it’s whisper quiet then an open start switch can be more of a possibility. It it has a dragging sound then less likely. If it has quite a bit of resistance then it points to other issues than the start switch.
 

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