If the LED has gone off there is no way to reset or do anything.. it would not help anyway as the power supply is now dead.
If you have applecare on a computer.. (sometimes ipad is accepted and sometimes not), and the TC is less than 3 years old, Apple should replace it. They will not recover files or do anything, and you will get a refurbished one with same size drive as the old one.
Otherwise you will need to repair the power supply, replace it with external power supply or get a repairer to fix it for you.
https://sites.google.com/site/lapastenague/a-deconstruction-of-routers-and-modem s/apple-time-capsule-repair
I listed several repair methods.. some very cheap.. and some people around the world who can help if you are unable to do it yourself.