p58

Definition:
an electrical measuring instrument in which instantaneous voltage and repetitive voltage wave shapes are viewed on the screen

What can you find with an oscilloscope that you would miss without it?

Alternators
Shorted or open stators and/or diodes in both the trio and rectifier assembly
A very slight drag from the rotor on the stator
If used properly the cycle time (on/off) of the regulator.
Bouncing brushes
Intermittent connections

Starters
Shorted armatures
Open armatures
Armatures that need to be re-soldered
A one lamination drag on the pole piece by the armature
The armature touching the hot brush lead

The scope is like adding another person to your company and their job is to catch what you’ve been missing.