I have a generator that I am attempting to fix, and I am getting readings that are out of spec on the rotor brushes. Per some instructional videos I found, I should be measuring 5V AC on the rotor brushes. I am measuring 65-70V AC. The video I was watching said that a high voltage reading (Assuming the brushes were good) indicated a bad rotor.
How can a rotor go bad (besides bearings and I'm sure I would notice other physical issues with the operation - the motor runs fine) and what are the electrical properties that cause it the voltage to read so much higher than nominal?
Edit: Per the question in the comments, this is a Duromax xp10000e (10000W peak) generator. The video I mentioned can be viewed here. I intentionally did not include that information originally because I was attempting to better understand the theory and principles at work, not just information related to my specific generator.