1. If the brush springs are damaged or have lost elasticity, replace them.
2. Check the ease of movement of the brushes in the brush holder. They should move freely, without jamming. Replace worn or chipped brushes. When replacing, solder the leads of the new brushes to the brush holder.
3. Clean the collector with fine sandpaper if it is dirty or there are marks, scratches, etc. on it. If the commutator is badly worn or burnt, replace the armature or gearbox with electric motor assembly. If there are signs of jamming on the necks of the anchor, clean the necks with fine sandpaper.
4. Replace gear with severely worn or broken teeth.
5. Straighten bent rods. If this is not possible, replace the linkage assemblies.
6. If the splines or threads of the pins are damaged, replace the linkage assemblies.
7. Clean burnt or oxidized contacts of the self-stop mechanism with fine sandpaper.
8. Replace torn, cracked, or loose rubber pads and other rubber parts.