Re: WorkCentre 6515 is making buzzing noises when inactive
If you're in the UK, call 0370 900 5501 and they should be able to schedule an engineer visit. They need to swap out part no. 105K31091 (LVPS PWBA 220V (SCC)), replacing it with the previous version of that part that doesn't have coil whine.
You first have to register the printer with Xerox before you can arrange an engineer visit. You can try to register online. That didn't work for me and it took several emails with the vendor and Xerox to get it registered so I could then arrange the engineer visit.
The engineer switched out LVPS PWBA for the previous part that was less energy efficient in standby but has no coil whine. After it was fixed all is good.
If you have driver problems (programs crashing when selecting the printer), then uninstall all drivers and software, then reinstall with the not recommended options (previous gen), e.g. choose Type 3 print system instead of type 4 print system. Same with PCL.