Try swapping left and right coil stops. Then replace the one that buzzes.

My imve coils buzz all the time. Thought that was normal stern behavior. Hmm...

The Stern flipper circuitry essentially pulses the current on/off very rapidly when the flipper is held up, and this can make the flippers buzz. All Stern games using that type of flipper control circuit buzz to a degree.

It can get much worse if parts are loose or start to get worn.

RM

Normal to a point. If the buzzing seems loud or excessive, or if one flipper buzzes a lot more than the other, check for loose parts that need tightening or worn parts.

RM

This really amazes me that Stern can design a flipper assembly like this that has been humming for years and they don't seem to care to modify or redesign it to try and get the hum out. Many hum a little bit but some hum pretty loud and despite the replies you will get IMO it's a spotty, trial and error fix, it's not just changing 1 part and that solves it.

My NIB AC/DC buzzes. It is normal. Just one of the perks of owning a Stern I guess!

Normal Stern behavior, although you will find some machines do it more than others. My Rolling Stones buzzes in a faint manner, but my Ripley's buzzes like crazy (even after a full flipper rebuild). It could be a thing where the White Star machines do it more noticeably (RBION, LOTR, etc).

It lets them use a single-wound coil and only one voltage.

That's why they do it (I assume).

RM