Execution order
1. Inspect the contact rings. If they have burrs, scratches, marks, traces of wear from brushes, etc., the rings must be ground. If the damage to the rings cannot be removed with sandpaper, turn the rings on a lathe, removing a minimum layer of metal, and then grind.
2. Check the rotor winding resistance with an ohmmeter by connecting it to the slip rings. The winding resistance should be 2.8–3.0 Ohms at a temperature of 20°C.
3. Check with a test lamp whether there is a short circuit between the winding and the rotor housing. Apply an alternating current of 220 V to one contact of the test lamp (you can use a battery and a 12V lamp). Connect the other lamp contact to the rotor body. Connect the second wire from the 220 V AC source to each contact ring in turn. In both cases, the lamp should not light. If the lamp lights in at least one case, then a short circuit occurs and the rotor or winding must be replaced.
4. Inspect the stator. There should be no traces of the rotor touching the stator on its inner surface. Otherwise, replace the rotor shaft bearings or generator cover.
5. Check if there is a short circuit between the stator windings and the housing. Apply 220 V alternating current to one contact of the test lamp (you can use a battery and a 12V lamp). Connect the other contact of the lamp to the stator winding terminal, and the second wire from the current source to the stator housing. The lamp should not light. If the lamp lights, there is a short circuit in the winding, therefore, the stator or winding must be replaced.
6. Check for a break in the stator winding. Apply 220 V alternating current to one contact of the test lamp (you can use a battery and a 12V lamp). Connect the other contact of the lamp to the housing. Connect the second wire from the current source to each winding terminal in turn. In all three cases, the lamp should light. If the lamp does not light in at least one case, then there is a break in the winding and the stator or winding must be replaced.
7. Inspect the generator covers. If cracks are found, especially in the places where the generator is attached, the covers must be replaced.
8. Check the ease of rotation of the bearings. If during their rotation there is play between the rings, rolling or jamming of the rolling elements, such bearings must be replaced. It is also necessary to replace bearings with damaged protective rings or traces of lubricant leakage.
9. Check the ease of movement of the brushes in the brush holder. If the brushes are jammed or move with difficulty, replace the brush holder assembly. The brush holder is also subject to replacement if the brushes have chips, cracks or other defects.
10. Check the size of the brushes protruding from the brush holder. If it is less than 5 mm, replace the brush holder.
[The text is based on materials from the website «AudiManual.ru»]