I have an Acer travelmate laptop which (by mistake) I dropped on the floor with the power jack side down, with the charger connected and it broke the DC jack from the inside of the laptop.
Then I unscrewed the laptop and soldered the DC jack back and then plugged it in and switched on the laptop without the batteries. It did switch on, that was before screwing everything back.
Then after assembling the whole thing back it does not power up. So I disassembled it again and just took the part which contained the DC jack (My laptop is like in two parts one contains the power jack which then sits on some pins on the main PCB) to a technician and he said that if you had connected this to a motherboard then it would have burnt cause the soldering was not right.
And then I checked with my laptop again by connecting everything the light (the charging light) comes on when I connect the power but it does not switch on.
Right now nothing is connected to the laptop; no HD, CD ROM, RAM , Battery. Nothing! Even then it does not power up.