I do not think it depends on the power supply. After doing some tests now works, in practice I think it is dconf-editor or the panel of the management of the various parameters that has some problems (such as automatic mounting of the usb) when the installation of the operating system on hd-usb takes place (at least I think). They are bugs that unfortunately are very difficult to solve because the cause is uncertain. You can help me to preview images and files. The solution on the desktop has not been resolved nor even on the notebook.
Thanks for the attention.