I'm really surprised that you've not received a response yet...! Perhaps this question would've received more help on the Hi-Rail forum?
Anyhow, typically the buzzing noise associated with the rotating radar screen accessory is associated with the AC 60hz voltage being applied. This is essential for an accessory such as the radar device because you're trying to get the movable item...the screen...attached to a steel armature plate to 'bounce' on the rubber finger grommet, thereby creating the rotating motion.
More to the point of the noise, however, is that it can be exacerbated by a loose solenoid coil. In other words, if the coil (intended to be stationary) is not firmly attached to its base detail, it will 'bounce' itself, adding to the overall buzzing sound.
Ergo, I would check to be sure that the accessory feature(s) that attach the solenoid coil is(are) doing so as solidly as can be expected. I seem to recall that there is a large speednut which retains the solenoid canister to the upper platform. If this is not firmly in place such that the canister can move you likely will have extra buzzing...sort of as you describe.
There are other issues related with the solenoid coil...loose windings, loose tape wrap, etc....as well as something on the tower assembly vibrating in a 'sympathetic' manner that can create extra, unwanted buzzing.
Some accessories that have solenoids can be silenced by the application of DC voltage. The radar tower, requiring the 'bouncing' magnetic field interacting with the screen armature, is not one of them. It must have AC voltage.
OR!....as covered in another thread and as I did with my Disney version of this tower... I replaced the entire solenoid/armature plate device with a Faller slo-motion motor. No more buzzing and no more worn out finger grommets. But it's somewhat an involved project.
Then there are those for whom the cacophonic noises of trains and accessories in this O3R hobby are part of the 'schtick'....the more the merrier. Some folks have been known to turn up the stereo....or turn down the hearing aid!!!
FWIW, always...
KD
