I have not used my phase converter in a while. When I fired it up the
other day, the main Allen Bradley size 2 starter made a very loud
noise, like a old style 60 Hz door buzzer. Despite that, the converter
ran, but I decided to not use it and investigate.

This is a Size 2 starter starting a 10 HP motor.

So.

What would be the proper troubleshooting procedure here and what is
likely wrong? Any ideas?

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