i suggest u find a new dc jack m8 🙂
it is a pain resoldering the old dc jack if the pins have physically snapped off
basically the black plastic block is called a 'dc jack', there is various pins on the dc jack based on laptop, what tends to happen is batteries die on laptops and the end user treats them like a mobile PC, moving em around with em plugged in, the stress and constant movement takes it toll on the pins and they tend to snap thus the laptop only charging when u fiddle with the power cable in the dc jack, eventually the laptop will not charge at all regardless of fiddling around
the bottom line is laptops are not designed to be moved when the power cable is plugged in, it is very very common fault atm as the end user cannot afford to replace the battery thus moving it around with it charging
also parents tend to give their kids laptops and expect them to be child proof when they are not
i personally do not do dc jacks as you quickly find out why they failed in the first place, then once repaired the end user comes back a few weeks / moths later moaning that the dc jack has failed again when clearly it is how the end user looks after the laptop
dc jacks are very time consuming and fiddly, for the cost of replacement many companies wont touch em due to the possibility of damaging other components