1. INSPECT ROTOR
(a) Check the rotor for open circuit.
Using an ohmmeter, check that there is continuity between the slip rings.
Standard resistance: 2.3 - 2.7 W at 20C (68F)
If there is no continuity, replace the rotor.
(b) Check the rotor for ground.
Using an ohmmeter, check that there is no continuity between the slip ring and rotor.
If there is continuity, replace the rotor.
(c) Check that the slip rings are not rough or scored.
If rough or scored, replace the rotor.
(d) Using vernier calipers, measure the slip ring diameter.
Standard diameter: 14.2 - 14.4 mm (0.559 - 0.567 in.) Minimum diameter: 14.0 mm (0.551 in.)
If the diameter is less than minimum, replace the rotor.
2. INSPECT BRUSHES
Using vernier caliper, measure the exposed brush length.
Standard exposed length: 10.5 mm (0.413 in.) Minimum exposed length: 4.5 mm (0.177 in.)
If the exposed length is less than minimum, replace the brushes and brush holder assembly.
3. INSPECT BEARING
Check the bearing is not rough or worn.
If necessary, replace the bearing (CH-1 1).