Lincoln Electric VANTAGE 400 Service Manual page 86

F-38
BRUSH AND SLIP RING SERVICE PROCEDURE (CONTINUED)
SLIP RINGS
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 suffi-
cient 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 connected to the carbon
brush and to the connection terminal.
5. If the slip rings are discolored, display evidence
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 the slip rings
being pitted and discolored from excessive arc-
ing. Another sign of sticking brushes is instabili-
ty 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.
TROUBLESHOOTING & REPAIR
FIGURE F.8 – BRUSH & SLIP RING LOCATIONS
VANTAGE® 400
BRUSHES
#201
7. If there is any evidence that the brushes may
have been sticking in the brush holders, 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 neces-
sary to clean them, using very fine, 500 or 600
grit sand paper 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 thorough-
ly blow the carbon, commutator stone, and
sandpaper dust from the machine before operat-
ing.
3. Perform the Case Cover Replacement
Procedure
Note: See Figure F.8 for general locations.
F-38
#200A
#200B