Rotor - Husqvarna DM 230 Workshop Manual

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ROTOR

Functional test
Preparations
Remove the inspection cover to the carbon brushes. Remove the screw to the
circuit board and fold this to the side to enable you to rotate the motor with
a screwdriver.
Remove the screws for the cable attachment to the carbon brushes. Put the
cable connections to the stator to one side ensuring these have no contact.
Connect a measuring cable to each carbon brush and connect to the measu-
ring instrument. The carbon brushes must be in good condition to make a
good contact to the collector.
Test cables
Use short test cables and lay these close to each other: the easiest way is to
twist them. Cables run in a coiled way give incorrect readings.
Inductance measurement – Henry (H)
Inductance measurement is applied to check the condition of the rotor. The
dimension is "Henry", abbreviated H (1H = 1000 mH). Resistance measure-
ment (ohm) produces no usable results.
Testing
Set the measuring instrument to measure mH. Turn the rotor shaft slowly once
ensuring you obtain the measured values for each winding of the rotor.
Measured values
A typical measured value for a whole rotor is around 12 mH. If any position
during the turn shows the values to be below 9 mH this indicates short-circuit
in the winding.
Bearing replacement
Lock the carbon brushes as
shown in the illustration.
Dismantle the gear box cover.
Warning!
You must not dismantle the
rotor by knocking the magnet
in the middle of the shaft!
Select a socket that fits the outer
ring and knock out the rotor.
Bearings and bearing holder
The ball bearing has a light force fitting to the bearing holder. This has two
O-rings that attach the bearing seat in the motor housing.
Refitting is facilitated by lubricating the O-rings.
Collector side – bearing
replacement
First remove the sensor. It has a
screw thread.
Bearing replacement
You do not need to remove the carbon
brushes. Lift up the carbon brushes as
shown in the illustration and lock the
carbon brushes with the spring lying to
the side.
Remove the four screws to the gear box
cover.
Warning!
The hexagonal magnet in the middle of
the shafts is the sensor for the motor's
speed control. You must not dismantle
the rotor by knocking the magnet.
Select a socket that fits the outer ring and
carefully knock out the rotor together
with the bearing from the motor housing.
Collector side – bearing replace-
ment
First remove the magnetic sensor in the
middle of the shaft. It has a screw thread.
Grip the rotor and remove the sensor.