Ask Max: USB hub intermittently functions
I recently bought a graphite iMac from you. I have added a [USB] hub. One day the hub will connect, the next day it will not. What is going on? I have an exact duplicate of the iMac at home with a hub that works every time I turn on the machine.
A USB hub can have connectivity issues due to a few different reasons. The connection point for the hub can be the largest barrier. A USB hub should be directly connected to the USB ports on the computer and not the keyboard or another hub. Also, not every USB port is equal, so try different USB ports to find the best connection. Another issue can come from the hub itself. Some USB hubs will have an external power adapter or have a port for an optional power adapter. This is because USB devices can be powered off a USB bus, but too many of these bus-powered devices will exceed what the computer can deliver. Without additional power the hub and the devices could stop working. A powered USB hub is a good thing to use, even if none of your devices are bus-powered. More hub problems can be caused by cables. USB cables can come in long lengths, but when connecting to a hub it is better to use cables 6 feet or shorter. Also some cheaper cables can fail randomly because of cheap metal wires or thin shielding. Try using known good cables for the main stretch between the USB hub and the computer.Hope that helps