I would not operate it until everything is checked out. First thing I would do, besides replacing the rollers, is to replace the cord, even if it was replaced at some point it still likely needs to be replaced. I would also inspect the internal wiring, from the pictures that wiring is original, and some of them may be frayed or cracked and could cause a short. I love the ZW, but it is still quite old and things decay over time.
Thank for the pointers. I did replace the cord and will also install a modern circuit breaker. All of the other wiring seems to be good shape. Right now, my main concern is making sure the piece of plastic I installed beneath the secondary coil is safe and won't melt or cause harm to the unit.