This post is for those who purchased a Rocktron Velocity 300 power amp and noticed the cooling fans dont turn on when unit gets hot. I just bought a new one (and like it), but noticed the thing gets really hot after about an hour of playing. The fans never come on. I emailed Rocktron and they said to open the unit and check a wire coming from the main board going to the cover. This wire has a little white plug on the end of it and plugs into a tiny green circuit board located just on the inside of the lid where the fans are. They said the connector on some units became unplugged during the assembly process. Sure enough, mine wasnt fully connected. I unplugged then plugged back in to make sure it was securely connected. When I tested, the fans eventually came on. The unit gets really hot, but the fans do their job and they are quiet. IMPORTANT! Be very careful when replacing the cover. When I did, the connector came unplugged again. Not only that, the plastic coating on one of the wires was cut slightly by the edge of the black heat sink, exposing bare wire. Theres practically no space between the connector and the heat sink (youll see what I mean when you open yours). I had to wrap a little electrical tape around the wire to fix. When replacing the lid, do so by closing the right side of the lid first (side with the fans), watching the plug carefully as you close the left side. I had to practice closing the lid several times before I actually connected the wire and closed it for good. There are two types of screws holding the lid on philips and hex. This sucks. I dont know why some manufacturers do this. Makes no sense. Good luck!