The power cord light does not lightup any more and will not charge the battery or run off A/C power.The light on the power pack box is lit and when I take a volt meter to the end plug there is no power when I touch one lead to the center electrode and the other lead to the outside of the plug.  There is a reading of 19.5v when I touch the lead on the volt meter to the outer plug and the inner part of the plug surface but not the center electrode.  I did notice the other day since I have battery bar I noticed it had showed it connected and disconnected on and off before it stoped working.  Is this a power cord issue or something more serious like the main plug on the laptop or mother board?