I inherited a large 220v Sanborn Compressor. I started it several times and it seemed to work fine so I ran air lines through out my garage and shop. When it was done, I flipped the breaker and ..... nothing. I got a humming sound for a few seconds and then it went silent. I've hit the reset button to no avail. If I turn off the breaker and then on within a few minutes, I don't get the humming sound until it's been off for a while. I'd like to turn the motor over by hand but I can't do that until I've removed the open cage protecting the pulleys and belt. Before I take off the cage, does anyone have any suggestions on what's going on with the unit?