The AC adapter
This part, like the batteries, is an essential element of your machine and is also the cause of a great number of breakdowns. Indeed, one of the elements most fragile of your laptop is the AC connector, i.e. the connector female in which comes to plug in the plug of your AC adapter.
The repetition of these plug in and sometimes their useless violence ends regularly up tearing off the female connector of the motherboard.
That often occurs by stage, initially light poor contact, then as you move the cable in all the directions to find the current, the connector is torn off definitively, or the produced sparks roast the motherboard.