Roland UM-4 Owner's Manual page 42

Troubleshooting
Is a Roland USB-compatible product other than the UM-4 connected to your computer?
If the UM-4 Driver is installed when a Roland USB-compatible device (UA-100 etc.) is
connected to your computer, the UM-4 Driver may not be installed correctly. If you wish to
simultaneously use both the UM-4 and another Roland USB-compatible device (such as the
UA-100) on the same computer, you must disconnect the other USB-compatible device from
the USB connector before installing the UM-4 Driver.
Case 2: USB connections cannot be made correctly
Has the UM-4 been recognized?
Disconnect the USB cables, and then re-connect them.
It is possible that the computer has failed to recognize or initialize the UM-4. Leave the USB
cable connected to the UM-4, and restart Windows. If connection still does not occur, exit
Windows, and turn off the power of your computer. Then turn on the power of your
computer and start Windows.
Are your computer or USB hub (*) supplying sufficient current?
If insufficient current is being supplied to the UM-4, connection is not possible.
• Use a USB hub which contains its own power supply.
• The power conservation mode settings of your computer may be limiting the current
supplied to the USB, so check these settings.
What is USB hub?
A "USB hub" is a device that expands the number of USB connectors. Broadly
speaking, there are two types of USB hubs.
Self-powered hubs (USB hubs containing a power supply): The USB hub itself has
an AC adapter, which supplies power (normally 500 mA) to the added USB connectors.
Bus-powered hubs (USB hubs not containing a power supply): The hub does not
contain a power supply. The power supply of the connected computer is re-distributed
to the added USB connectors.
For details on the electrical current that can be supplied by your computer or USB
hub refer to the owner's manual for your equipment. If you have questions, please
contact the manufacturer or dealer for your computer or USB hub.
The UM-4 cannot be used with a hub that contains no power supply.
When a USB device is connected to a computer, the USB device tells the computer
how much electrical current it uses. If this value exceeds the current that the
computer is able to provide (maximum 500 mA), the device cannot be connected.
The UM-4 will request 150 mA of current when it is connected to a computer.
Most computers or self-powered USB hubs will have no problem with this current
capacity. If you are using a dual-mode USB hub (self-powered / bus-powered), be
sure to connect its power supply (AC adapter etc.) and use it as a self-powered
USB hub.
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