Brush motor for shark vacuum

Thread Starter

Wireman10

Joined Dec 30, 2022
6
The brush motor on my shark vacuum stopped turning. I have 120v getting to the PCB. I checked both limit switches for the recline position of the vacuum and for the brush shield and both are functioning correctly. The brush motor has 4 leads going to it. A brown and white which are about a 16ga wire and a black and red which are about 20ga. All 4 come from the PCB. Brown is labeled M1, white is labeled M-, I cannot read the red and black. When I turn the vacuum on I am only getting 60 volts across the brown and white wire. The motor nameplate is for 120V. I’m confused why there are 4 leads to the motor and why there is only 60v across two of the leads. Does this motor use brushes? Are two leads going to the stator and two for the rotor. Why would I only have 60V. Any explanation on the theory behind this motor is appreciated. There is 11 ohms across the brown and white leads and 59k ohms across the red and black leads. Thanks,
 

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PaulEE

Joined Dec 23, 2011
474
Man, this is gonna be a steep hill to climb to figure out what is going on with this thing. I'm sure someone knows, but they're normal and celebrating new year's somewhere. I am not, so you're stuck with me! :)
If you do your ohm measurements like you did, when you got 56K, does that reading change when you slowly turn the shaft of the motor?

Paul
KI5VNH
 

MisterBill2

Joined Jan 23, 2018
17,777
The appearance of the motor is that it is a brush type of DC motor, and the brushes may be worn out, that does happen.
But the first question is about the rest of the system: Does the main vacuum blower motor run? Does any portion of the device operate correctly?
The most common failure is that the brush mechanism becomes jammed and will not turn at all. So the first question is if the motor turns freely.
A 120 volt DC motor should spin at 60 volts if it is free to rotate and the brushes are OK.

In the photos it looks like there might be some smoke stains on the circuit board, although that might just be poor lighting. All that I see in the board are capacitors and one thing that looks like a power transistor. To accurately evaluate the motor you will need to unplug it from the circuit board to check the resistance with your ohm meter.It should be much less than 56K ohms, probably just a very few hundred ohms.
 

shortbus

Joined Sep 30, 2009
10,044
The appearance of the motor is that it is a brush type of DC motor,
Guess you never heard of universal motors, their in many, many small appliances and most corded power tools. But then again I'm wrong and throwing stones for bringing up your knowledge level.
 

MisterBill2

Joined Jan 23, 2018
17,777
Certainly this could also be a universal motor, no doubt. BUT the applications that include a circuit board and filter capacitors often have DC brushed motors. I did go back and examine that first photo and it does show the label that does state 120 volts AC.
In addition, even a field coil universal motor should turn a bit with no load and 60 volts applied . And now I see that it is the stall detect device that is 56K and the motor winding is 11 ohms.
So you did get me on this one, Shorty.
So once again, does the motor spin freely? If it stalls then the stall detect should reduce the power.
 

MaxHeadRoom

Joined Jul 18, 2013
28,507
We have a Shark Vacuum and that is the beater-bar motor, it is marked 120v 60Hz and a brushed motor, so certainly a Universal version.
Not sure if it is the same model as the OP's?
 

Thread Starter

Wireman10

Joined Dec 30, 2022
6
The motor spins freely by hand. I pulled the belt to take away any load from the motor to make sure that wasn’t the issue. The only thing I find odd with spinning the motor shaft is that it doesn’t spin “smoothe”. I work with larger 3 phase motors and those motors turn very smooth unless they have a bad bearing. This motor turns but it doesn’t feel great. It doesn’t feel like a bad bearing necessarily almost like the shaft turns free for 20 degrees and then finds a “notch” and then turns good for 20 degrees, etc. Should a small universal motor feel like this when turning the shaft?? If it was a larger motor I would immediately say there is a bind on the shaft but I don’t have a good feel for these smaller motors. What is a stall detect device? I am not familiar with that. I guess the question still remains, should I replace the motor or control board? I am leaning towards the motor because of how the shaft feels when I rotate it BUT I cannot make sense of why the control board would only supply 60V to the motor?? The windings on the motor seem good, 11 ohms across them which for a small motor like this seems reasonable to me. Thoughts?
 

Thread Starter

Wireman10

Joined Dec 30, 2022
6
Still waiting for the picture of the underside of the board :)
Paul
KI5VNH
Right. Sorry about that. I very much appreciate the help and knowledge sharing. This is fun stuff. Underside of board pics attached. It might be helpful to know the components going to this board. There is a set of LED lights for the vacuum, a limit switch for the recline position, a limit switch for the brush guard and the brush roller motor. I don’t see any visible damage to circuit board, no burned areas or anything like that, nothing obvious.
 

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Thread Starter

Wireman10

Joined Dec 30, 2022
6
There is a brush indicator light on the board as well. The light doesn’t come on. No green, no blinking red, just nothing
 

PaulEE

Joined Dec 23, 2011
474
My gut reaction when I saw your first images was a DC motor being fed by pulses of rectified AC.

I have no idea whether this is ever done, but man…that’s A LOT of business on the back of that board for a simple motor.

I’m also wondering about that 3-pin power device with a pin going over a slit in the board. My gut reaction to that was a TRIAC or high-side switch.

The motor, honestly, sounds OK to me. It sounds like the typical “indents” you would feel on a brushed motor. Sounding okay and being okay are two different things, though.

Forgive me if you mentioned this already, but when you measure windings, are you attaching the meter and slowly turning the motor to get 11 ohm readings?

Paul
KI5VNH
 

MisterBill2

Joined Jan 23, 2018
17,777
It seems to me like it should be possible to temporarily disconnect the brush bar motor from the circuit board and see if it runs. Given that it is rated for mains voltage that should be simple to do. But leave the motor mounted and connected with the drive belt so that any mechanical issues will be revealed. If the motor operates correctly then it is not the problem. The problem would either be on the PCB or the external on/off switch for the motor. Or some other motor control part.
 

MisterBill2

Joined Jan 23, 2018
17,777
One more suggestion and then a second . Put the belt back on and see how well it turns. Then disconnect the motor from the PCB and power it directly from the mains, 120 volts. If itruns, then you know the problem is not the motor. A simple and cheap test that does not need many tools and needs no measuring devices.
 
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