I have a 4s that won't boot. It will show the apple logo but then the apple logo dims for a second then turns off. ITunes will recognise then phone but when I try to restore it will die just after the loading circle. Right before the progress bar is supposed to appear. I can force the phone out of recovery mode but it just starts the boot crash loop Has anyone got any ideas how to sort this? I can get into dfu mode but nothing changes.