Glo no more light for the night in my Kobo

The light of my Kobo Glo went out this night.
I can use the reader but there is no more light.
If i turn on the light nothing happen, I can manage the level, but nothing occurs.

I tried to reset with a pin.
I tried the hard reset without succes.

Is there a kind of electric bulb inside? Has anyone already changed it?

thank you for the help and sorry for my bad english.