from your earlier post where you stated that the unit fell with the cord plugged in my guess would be the coaxial socket on the n800.
I have fixed laptops with the same problem by soldering wires to the charge input pionts and tieing a knot in the wire to keep it from pulling out through charging port. then attach a female in-line coaxial plug and replace the tip on your charging cord with one that fits the plug.

not elegant but functional.