I have just purchased a slimline external Blu-Ray DVD/RW drive with a USB 2.0 port and a 5V socket. A second cable is supplied that connects a second computer USB port to the 5V socket.
When I try to power the device via it's USB port I get a USB power surge error message on the computer. This is also the case if I also connect the 5V socket to a second USB port for extra current supply.
The drive does work when I use a mains 1A USB power supply connected to the 5V socket.
I tested the drive USB port with PC Wizard and found that it uses an Initio SATA-USB bridge Chip. However the USB descriptor "Max. Power" entry reported for this chip is only 2mA. I know that this value is generally specified in 2mA increments, however even my USB mouse specifies 100mA (50 units).
If the computer USB port responds by limiting the current supply to 2mA, and reports a power surge if a greater current flows, this would explain the problem.
A second problem is that the drive starts to hunt (repeatedly makes a double click with periodic motor sound and flashes drive light) when the computer powers down or the USB cable is disconnected and there is a disc inside. This does not happen on an older 3-1/2" DVD/RW drive that I have.
Is there any way to fix the Max. Power 2mA problem short of getting a replacement drive ?
Should the drive continuously hunt if a USB connection is not made to the USB port ?
Although 5v should be available at a USB port, another factor to bear in mind is how many watts the device draws, and it's probably more than what is available without using a mains-powered USB hub. The only options you have therefore is to always use a mains-powered hub for that DVD drive, or buy one which comes with a mains-adapter which plugs into a mains power socket.