INTERNAL USE - NOT FOR WEB. (OK to share with customers in need of this info)

The internal fan has probably gone bad. This is rare, but it occasionally wears out.

The customer can easily pop the top off the unit, turn it on, and listen for the noise. they should be able t locate the noise more easily.

To be sure it's a bad fan, the customer should turn the unit off, trace the power wire from the fan to the power supply, and disconect that wire. If they turn the unit on and the noise is gone, it's the fan.

Presonus will usually send the customer a new fan free of charge. It is apparently quite easy to replace this fan.