Help with Theta Gen Va?

While doing some cleaning around my equipment rack, I noticed a slight buzzing coming from my Theta Gen Va. To make sure, I unplugged the Theta and the buzzing stopped. It is not loud enough to hear if more than a foot or so away from the equipment, but I'm still not sure whether it should be doing this.

This is probably the power transformer, but I don't recall whether it has always made this noise or is a something new. Can someone else with a Gen Va check for this sound and let me know what you find?

Thanks,