Is this the triple-coaxial plugs they use on Dells? The outer barrel is
gnd, the inner side of the barrel is +19.5 V, the center pin is some
resistor or something that classifies the power supply's capacity.
I'm not exactly sure what kind of contacts are in the laptop's socket, the
supply's plug doesn't have any springy parts in it. I'd guess the laptop's
socket contacts have gotten worn or lost their spring temper.
Jon