A feignt buzzing indicates that either there is a blockage preventing the impellor from rotating or the motor start capacitor has blown due to constantly overloading the machine.
If on checking there is no blockage then without telling you to pop off to maplins and buy a 12 mf 440v ac motor start capacitor for a few pounds and installing it in the machine you will have to get a saniflo service engineer in ..
Mike
May 2012