There is a quick way to boot the device to maintanance mode and telnet into it. This would make sure if the problem is indeed the screen or if the device does not boot at all. Get my MOSLO based maintanance boot from svn repository; "svn co https://toosa.swagman.org/svn/sillykbd/TRUNK/moslo", and have a look at the README file for details. If you can telnet to the device you can be sure it's just the screen that is broken. Also, you can manually export your mmcblk partition via the USB connection to take backup on external PC, if you for example need to send the device for repair.
[38569.715228] usb 3-1: new high-speed USB device number 20 using xhci_hcd [38569.738659] usb 3-1: New USB device found, idVendor=0421, idProduct=0105 [38569.738664] usb 3-1: New USB device strings: Mfr=1, Product=2, SerialNumber=5 [38569.738667] usb 3-1: Product: N9 (Update mode) [38569.738669] usb 3-1: Manufacturer: Nokia [38569.738672] usb 3-1: SerialNumber: 357923049514963 [38570.162778] usb 3-1: USB disconnect, device number 20