TROUBLESHOOTING & REPAIR
F-38 F-38
RANGER 305D
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BRUSH AND SLIP RING SERVICE PROCEDURE (continued)TEST PROCEDURE
1. Perform the Case Cover Removal
Procedure
2. Examine brushes and slip rings. The slip
rings, brush holder,and brushes should be
clean and free from oil or grease. The
brushes should be making good, continuous
contact with the slip rings.
3. The brushes should be of sufficient length
and have adequate spring tension.
Generally,the brushes should be replaced if
either brush has less than 1/4” remaining
before it reaches the end of its travel.
Spring tension should be sufficient to hold
the brushes firmly against the slip rings.
4. The brushes should be removed from the
brush holder and examined. The terminals
should be clean. The shunt, (braided lead
connecting the carbon brush to the terminal)
should be in good condition and firmly con-
nected to the carbon brush and to the con-
nection terminal.
5. If the slip rings are discolored, display evi-
dence of excessive sparking, or the brushes
have worn prematurely; these may be signs
of a grounded or shorted rotor. Perform the
rotor resistance test.
6. Check for evidence of sticking brushes.
Sticking brushes will normally result in th
slip rings being pitted and discolored from
excessive arcing. Another sign of sticking
brushes is instability or loss of both weld
and auxiliary output, but the machine may
begin to work properly,for a short time, after
being jarred or moved.
7. If there is any evidence that the brushes
may have been sticking in the brush hold-
ers, a new brush holder and brush assembly
should be installed..
Cleaning slip rings:
1. In the event that the slip rings have become
dirty,discolored or mildly pitted, it will be
necessary to clean them, using very fine,
500 or 600 grit emery cloth or a 220 or 320
grit commutator stone.
Seating Brushes:
1. If brushes have been replaced, repositioned,
or are not making full contact with the slip
rings, it may be necessary to re-seat them.
This can be done by placing a strip of 180
grit sandpaper between the slip rings and
the brushes, with the abrasive side against
the brushes. Pull the sandpaper strip
around the circumference of the slip rings in
the direction of rotor rotation only. Repeat
this procedure until the surface of each
brush is in full contact with its matching slip
ring.
2. Use a low pressure compressed air to thor-
oughly blow the carbon, commutator stone,
and sandpaper dust from the machine
before operating.
3. Perform the Case Cover Replacement
Procedure.
Note: See Figure F.9for general locations.