Sometimes fans just die. When they do, there can be an open circuit that will cause a hum. Replacing the fan will not only restore the airflow, but will often make the hum disappear again, as well.
If you're not afraid to remove the cover (make sure the unit is unplugged), these fans are very easy to replace, only being held in place by 4 screws and connected with a single connector on the circuit board.
You likely have already gotten this fixed, but if not, replacing a worn out fan is a fairly easy process, and a very inexpensive repair.
Answers & Comments
Sometimes fans just die. When they do, there can be an open circuit that will cause a hum. Replacing the fan will not only restore the airflow, but will often make the hum disappear again, as well.
If you're not afraid to remove the cover (make sure the unit is unplugged), these fans are very easy to replace, only being held in place by 4 screws and connected with a single connector on the circuit board.
You likely have already gotten this fixed, but if not, replacing a worn out fan is a fairly easy process, and a very inexpensive repair.
THere can be various causes, none of which will be user serviceable. Contact Behringer for the nearest service center. Here is the link-
Behringer Bugera Portal Starin Distributing