Check working surfaces of contact rings. On them there should not be agnails or chips.

Fig. 7.25. Measurement of diameter of contact rings

Measure by a caliper diameter of contact rings (fig. 7.25).

Standard diameter: 14,2–14,4 mm.

Minimum admissible: 12,8 mm.

If diameter of contact rings is less minimum admissible, the rotor needs to be replaced.