It's the cord because when I plug the adapter to the source, it makes a
noise - and when I mess with the cable, the sound changes. The problem
seems to be at the origin of the cable near the adapter.

Anyway.. This case is dead. Dell won't help, because I'm in South Korea
and they don't support my Inspiron 9400/E1405.
I'll try eBay!
Thanks a lot!