warc s Fig B 43 Armature Test for Shorts vibrates armature is shorted Recheck after cleaning between the commutator bars If saw blade still vibrates replace the armature Armature Test for Ground Place one lead on the armature core or shaft and the other on the commutator fig 8 44 If the lamp lights the armature is grounded and must be replaced Fig 8 44 Armature Test for Ground Field Coil Test for Open Circuit Place one lead on each end of the field coils fig 8 45 If the lamp does not light the field coils are open and will require replacement Field Coil Test for Ground Place one lead on the connector bar and the other on the field frame fig 8 46 If the lamp lights the field coils are grounded Repairs Loose Electrical Connections When an open soldered connection of the armature to commutator leads is found during inspection it may be resoldered provided resin flux is used for soldering CAUTION Acid flux must never be used on electrical connections r Fig B 45 Field Coil Test for Open Circuit Turning the Commutator When inspection shows commutator roughness it should be cleaned as follows 1 Turn down commutator in a lathe until it is thoroughly cleaned CAUTION Do not cut beyond section previously turned 2 Undercut insulation between commutator bars 32 This undercut must be the full width of insulation and flat at the bottom a triangular groove will not be satisfactory After undercutting the slots should be cleaned out carefully to remove any dirt and copper dust 3 Sand the commutator lightly with No 00 sandpaper to remove any slight burrs left from undercutting Fig B 46 Field Coil Test for Ground