Old school diagnosis, armature on a growler check out the manual : r/ Justrolledintotheshop
Mike] Shows Us How To Use An Armature Growler
Growler DC Generator Starter Armature Testing
Antique Armature Testing Growler [Restoration]
Armature Growler Tester Model 6054
Growlers
TESTING ARMATURES with a GROWLER #761 tubalcain sun commutator
Armature Growler Tester
Armature Growler Tester
Armature Growler Tester Model 6054
How a growler is used to test armatures
HOW TO USE AN ARMATURE GROWLER