I can't post a link to the imgur gallery of "screenshots", so you'll have to add this a/0y7Ia manually
Came across a 1520 which seems to be stuck in some sort of boot loop. It turns on, allows you to go in to a diagnostics/test mode, then restarts and brings you back to the beginning. I don't know the history of the phone, so I can't provide anymore helpful information. I've tried both Nokia Care Suite and Nokia Software recovery tool, but neither tool will recognize the device. Any ideas?