Lincoln Electric SVM194-A 24TROUBLESHOOTING and REPAIRF-24, Procedure, Cleaning the Slip Rings

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F-24TROUBLESHOOTING AND REPAIRF-24

BRUSH & SLIP RING SERVICE PROCEDURE (continued)

(Exciter/Auxiliary Power Alternator)

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PROCEDURE

1. Remove the round end cover from the exciter.

2. Examine brushes, slip rings and brush holder.

• Brushes should be clean and free of oil and grease.

• 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 itʼs travel.)

• Brushes should be making good, continuous contact with the slip rings, and should be rid- ing near the center of the slip rings. (The brush holder bracket may need to be slightly bent to achieve acceptable alignment.)

Note: If slip rings are very dark in color, display evidence of excessive arcing, or a have worn prematurely, these may be signs of a grounded or shorted rotor. Perform the

Exciter Rotor Resistance and Ground Test.

3. Check for evidence of sticking brushes. Sticking brushes will normally result in the slip rings being pitted and discolored from exces- sive arcing. Another sign of sticking brushes is instability or loss of both weld and auxiliary out- put, but the machine may begin to work proper- ly for a short time after being jarred or moved. 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 the Slip Rings

In the event that the slip rings become dirty, discol- ored or mildly pitted, it is necessary to clean them using a very fine 500 or 600 grit emery cloth.

CAUTION

A 220 or 320 grit commutator stone may be used. Commutator stones should only be used by expe- rienced technicians who have the knowledge and proper equipment to use them safely.

Seating Brushes

If brushes have been replaced, repositioned or are not making full contact with the slip rings, it will 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. Make sure the abrasive side is against the brushes. Pull the strip around the circumference of the slip rings in the direction of the rotor rotation only. Repeat this procedure until the surface of each brush is in full contact with its matching slip ring.

Use low pressure compressed air to thoroughly blow the carbon, commutator stone and sandpaper dust from the machine before operating.

Securely connect the leads to the brush terminals (see wiring diagram) and replace the alternator cover if testing and service is complete.

CLASSIC® 300D & 300G