Replacing the Braun MultiQuick 9 Type 4200 motor brushes

ID: 194563

Description: Replacing the carbon brushes (motor brushes)....

It may be possible to do this without a knife, simply by squeezing. Alternatively, you can use a knife without a serrated edge to avoid damaging the rubber seal and the housing.
Carefully squeeze the mixer in a vise using soft wooden jaws. Insert the knife 2–3 cm and pull it back out.
Then rotate the mixer 5–10°, squeeze it again, and reinsert the knife. Repeat until you have worked your way all the way around.
Slightly press in the buttons at the two attachment latches so that the knife can pass by them.
Markers: Red = knife tip, Green = approximate location of the seal, Blue = pressure from the vise.

Once you have worked your way all the way around, remove the mixer from the vise.
The motor should then be easy to pull out of the housing.

Now inspect the carbon brushes. If the contact spring is resting on the housing of the rotor, the carbon brush is completely worn; there is about 3 mm left. The spring can no longer press them against the commutator of the rotor, and the motor stutters. A "good" carbon brush still has about 3 mm of spring travel remaining.
New carbon brushes have the dimensions 6 x 3 x 8 mm (L x W x H), perhaps 6 x 3 x 9 mm. They must not be 10 mm, because then the tip of the spring would stand too high and might scrape against the housing or be pushed away during reassembly. 6 x 3 x 8 mm brushes are available from coffee machine spare parts retailers, approx. 8 €/pair.
To remove the carbon brushes, take the spring out of the slot in the shaft and, for example, wedge a small flathead screwdriver underneath to hold it away from the shaft. Remove the carbon brush with tweezers or, if it is too short to grip, carefully tap it out upside down.
Inspect the contacts of the commutator through the empty shaft; rotate the motor from the front to do this.
If you have removed the motor and the PCB, clean everything of carbon dust.
If you have only managed to pull the motor out of the housing and the shaft is still closed at the top, try to blow the whole thing out thoroughly (outside!) with compressed air. To do this, remove the cover on the front handle (around the trigger); it is only clipped on. Then the dirt can come out there.

When reassembling, pay attention to the orientation of the PCB: On one side, it has a contact surface that matches the pin contacts on the motor, and on the other side, there is only a notch. It is actually difficult to assemble incorrectly.
If you only managed to pull the motor out of the housing, pay attention to the orientation when reinserting it and aim as precisely as possible along the axis towards the connections so that the contacts are aligned.

Find suitable screws; 2 are probably enough, I used 4. For example, from salvaged children's toys or any simple devices. The main thing is that they are small, for plastic, approx. 3-4 mm long, with a thread diameter of approx. 1.5 to 2 mm.
Place them on opposite sides of the housing. I used the edges of the locking buttons as a guide. Position the holes approx. 1 mm above the edge of the locking button surround so that the seal is hit well.
With the motor inserted, carefully pre-drill (e.g., using a 1 mm drill bit for a 1.5 mm screw). Remove the motor and check that the holes have properly hit the seal ring on the motor. Test with one screw, check the depth, and shorten the screw if necessary.
When everything fits, insert the motor and screw it in tight.
General tip: Always insert screws into plastic by first turning them up to 1 turn backward (i.e., counter-clockwise!) until you reach the position where the screw noticeably "drops" into the existing thread in the plastic. This ensures you align with the correct thread again. Otherwise, the screw will cut a new thread, which might work 1-2 times, but then it will never hold again.

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