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Smoking Electric Lawn Mower

34442 Views 5 Replies 2 Participants Last post by  SABL
Hi all,

I have a Black and Decker MM275. When I plug it in and turn it on there's a slight hum and then smoke comes from the motor.

I opened the casing and flipped the switch again to see what the problem was. The smoke comes from the connection between the motor and a little plate pushed by springs that connects to the bridge rectifier. The metal immediately between the motor and the plate turns red hot and starts smoking. It only smokes on the positive side of the motor connection. But afterwards the brass casing holding the springs on both sides are hot to the touch.

I have attached a picture of where the problem is. It's not my mower but it's the same model.

I don't think the wiring has any problems but I'm not too familiar with motors in general so if anyone has any advice that would be great!


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Hi ftwow...welcome to TSF!!

With any luck you may not have damaged the armature (the portion that spins) in your motor. The parts you have noted in the picture are the brushes.... there should be no metal plate coming into contact with the armature. The brushes are made of carbon and do wear out (I've replaced many in my power tools). If not replaced before the spring makes contact with the armature the result will be motor failure and, most often, an expensive repair.

Part #242274-00 for the brushes @ $1.75 ea
Part #242028-08 for the armature @ $113.00

B&D Parts

If you are not familiar with electric motors I would suggest you find a local service center.
Well I don't think the brushes are damaged.

I tried turning the blade manually and it turns very roughly like there's rust or something jamming perhaps the ball bearing?

If the ball bearing is jammed would it cause the motor to start smoking?
Yes, a seized bearing will cause the same symptom. I was going by your description of metal coming into contact with the armature. Most bearings are sealed but you may be able to work some light grease into them if you can carefully pry the plastic seal off of the side of bearing....usually a black band that covers the steel balls. If any balls are missing the bearing must be replaced... there should be a number engraved on the side of the bearing and a good auto parts store can replace most bearings.
thanks so much for the advice! I'll give it a shot.
Good luck....let us know how it goes!!
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