Brother “Unusable Device” Message
The machine's USB host/direct interface detected a USB device that is unsupported, defective, or drawing more power than the port allows.
Error meaning
The USB host/direct interface detected an unsupported, defective, or excessive-power USB device.
This meaning is tied to the reviewed family/platform and subsystem below; do not reuse the number or wording by itself on a different printer family or protocol.
Applies to
Brother current color-laser models explicitly listed for Unusable Device
- HL-EX470W
- HL-L3295CDW
- HL-L8245CDW
- HL-L9410CDN
- HL-L9430CDN
- HL-L9470CDN
- MFC-EX670W
- MFC-L3765CDW
- MFC-L3780CDW
- MFC-L8395CDW
- MFC-L9610CDN
- MFC-L9630CDN
- MFC-L9670CDN
Common formatting
These are formatting/lookup aliases for this reviewed condition, not separate error pages.
- Unusable Device
- unusable-device
What usually causes it
- A USB flash drive or other device type is not supported by the printer's direct USB port.
- The connected USB device is damaged or malfunctioning.
- The device draws more power than the printer's USB host port is designed to supply.
What to try
Remove the device from the printer's USB host/direct port
This message concerns the printer's accessory/direct USB connection, not the USB cable between a printer and computer.
Restart the printer with that device disconnected
Confirm the message clears before reconnecting anything.
Check whether the USB device type is supported
Use Brother's model documentation for supported direct-print/storage devices. Do not assume every USB accessory can be powered or used by the printer.
Try a known-good supported device if you need the direct USB feature
If another supported low-power device works normally, replace the original USB device rather than changing printer drivers or network settings.
After each corrective action
Retry the same operation that produced Unusable Device. If it now works, stop there rather than changing unrelated printer, network, supply, or service settings.
If the code returns
If Unusable Device appears with nothing connected to the USB host/direct interface, or with multiple known-good supported devices, record the exact model and port condition for Brother support.
When service may be needed
Do not bypass USB power limits or use adapters intended to force an unsupported device. Persistent errors with the port empty or with supported devices may require Brother service.
Continue with guided troubleshooting
If the printer still is not working after the reviewed checks, carry this verified error context into the guided troubleshooter.
Related information
Verified source
Official Brother FAQ defines unsupported, defective, or excessive-power USB host/direct-interface causes and supplies a Related Models list.