If the lamp does not turn on, this may be because, by default, Windows tries to disable a USB port when the HP ScanJet scanner is not in use in order to save power.

1. In File Explorer, right-click "Computer" or "This PC", and then click Properties. The "System Properties" window will open.
   
   
2. Click the Hardware tab, and then the Device Manager button. The "Device Manager" window will open.
   
   
3. Double-click the Universal Serial Bus controllers branch to expand it.
   
   
4. Right-click USB Root Hub, and then choose Properties. The "USB Root Hub Properties" window will open.
   
   
5. Click the Power Management tab.
   
   
6. Remove the check from the "Allow the computer to turn off this device to save power" checkbox.
   
   
7. Click OK, and close the "USB Root Hub Properties" window.
   
   
8. Close any other open windows.

Outcome

The scanner will power on.