Jet JBS motor

[Bob Barris]

I have an old Jet band saw model JBS MW 14 and the motor burnt out, I mean it popped and smoked up the whole shop. Does anyone know where I can buy a motor for it ? I will also need a switch because the old one jammed. I could not find an original switch for it so I bought a heavy duty switch from a hardware and used it. I am afraid this may have caused the motor problem. I am not an expert on the electrical system of these old tools by any means. But I wonder if maybe the switch was not getting enough amps to the motor and caused the burn out. It was a good old saw, I used it for resawing. Thanks for any help.

[Bruce Wrenn]

Odds are that motor is a NEMA 56 frame, 1725RPM motor, and most likely either 1/2 or 3/4 HP, which is a little undersized for resawing. Problem may not be as bad as you think. When you said "popped and smelled up the whole shop," this tells me the start capacitor bit the dust. It is located under a "hump" on side of motor. When you open up hump, you will see a cylinder with two wires connected to it. Probably smell burnt and have some oil on it. Check values and contact a motor shop for replacement. If motor is truely trash, then most likely motor shop will have a rebuilt motor in the 1 - 2 HP range that will be a direct swap onto your saw. I don't see a location in your post which would help find someone close to you to trouble shoot your problem.

[Bob Barris]

Thanks Bruce what you are saying makes sense. The motor was really hot I could not hold my hand on it. I will check the capacitor today. The motor is a one horse and the saw has performed well for many years. This problem occurred within a month of replacing the on/off switch with one that was not a manufacturers exact replacement part. Could an improper switch cause this problem by changing the amps to the motor. I live in Belmont County in southeastern Ohio. Thank you for your help.

[Bob Barris]

I took the capacitor out and under the plastic cover on one end it does have a residue so it might have blown out. However it test OK on a swing meter, I am not sure that is conclusive. I will see if I can find one locally and change it. It is a Seika type 125, 125 VAC, 150 MFD, 35 x 61 mm. The motor is free and smooth with the belt off.

[Mike Henderson]

Hook up power to your motor (with the starting cap removed). As soon as you turn the power on, give it a good spin (in either direction). If it runs up to speed, and doesn't overheat when you run it for a few minutes (5-10), your problem is probably the starting cap.

If it won't run up to speed and gets hot, the motor is probably shot.

To give it a good kickstart, you can wrap some rope around the shaft and pull it to get it going good. Just make sure the rope will come loose and don't wrap it around your hand in case it doesn't. But most of the time, you can spin the shaft with your hand and that will be enough.

Alternately, you can give it a good spin and then turn the power on. Either way will work.

Mike

[Bob Barris]

Thanks for the tip. The motor started without even spinning it, but it ran less than 2 minutes and started smoking and the bottom got hot. So I guess I will be looking for a motor. This is my fault, I had to replace the switch and the one I used was not compatible with the motor. Pretty dang stupid of me.
Any suggestions where I can find a motor ??

[Mike Gresham]

Thanks for the tip. The motor started without even spinning it, but it ran less than 2 minutes and started smoking and the bottom got hot. So I guess I will be looking for a motor. This is my fault, I had to replace the switch and the one I used was not compatible with the motor. Pretty dang stupid of me.
Any suggestions where I can find a motor ??

I'm curious. Why would the switch toast the motor? That would have never occurred to me.

[Bob Barris]

Well it either had to many or not enough amps. I read somewhere that it will cause a motor to over heat and burn up.

[Mike Henderson]

Thanks for the tip. The motor started without even spinning it, but it ran less than 2 minutes and started smoking and the bottom got hot. So I guess I will be looking for a motor. This is my fault, I had to replace the switch and the one I used was not compatible with the motor. Pretty dang stupid of me.
Any suggestions where I can find a motor ??

One more thing to check before you give up on the motor. It's a long shot but worth taking.

Disassemble the motor (normally you just have to take one end off) and pull out the rotor. Check the centrifugal switch and make sure it will operate easily. Sometimes (not very often) the switch will get stuck closed and it won't open when the motor gets up to speed. This keeps the starting coil in the circuit and can overheat the motor.

While a "smoked" motor is bad, I've seen motors that got hot and once the problem was corrected, they ran fine for many years. But we're into the exceptions here.

Changing the switch almost certainly did not cause the problem unless you also inadvertently changed the motor from 240V operation to 120V operation. The motor has only two wires bringing power to it - whether it's 240V or 120V - and as long as you had the correct power on those two wires, changing the switch wouldn't affect the motor. I can't think of anything the switch could do to the power that would affect the motor, especially if the motor was not loaded when it failed.

Mike

[Bob Barris]

Thanks again Mike I will check the motor. It really runs nice and smooth until it gets hot.

[Bob Barris]

I took that motor apart and half of the windings are black and a couple are burnt clear through. I guess it is smoked.

[Mike Henderson]

I took that motor apart and half of the windings are black and a couple are burnt clear through. I guess it is smoked.

Sounds like it. Sorry.

Mike

[Bob Barris]

Thanks for all of your help. Now I go motor hunting.

[Peter Aeschliman]

Thanks for all of your help. Now I go motor hunting.

Bob, are you in the Seattle area by chance? I have an older jet bandsaw (the blue color) that I upgraded to a 2hp baldor motor a few years back. The previous motor has been sitting unused since then. Yours for free if you want it!

[Bob Barris]

Thanks for the offer Peter if I was anywhere close I would come after it but I am in Ohio.