ONSITE SLIP-RING & COMMUTATOR RESURFACING AND SERVICING

The commutator surface under the brush should take on a darker bronze color after several hours of operation. This is due to self-generated film caused by normal commutation. This coloration should be even, without blotches or black areas. A shiny copper color or black streaks in the brush tracks are signs of improper commutation or contamination by a foreign material.