There is variety of DC jacks in the laptop market which is little bit confusing. Every laptop company makes his own DC jack models. And even from the same company we get different kind of DC jacks for different models. Good thing is that 99 percent of laptop companies uses 19V as power source. And we are fortunate enough that the laptop power jacks almost most of the come with the two pins for the plus and the minus pin.

The variety of implementation can be simplified to the one concept of a DC jack with a connector ow inner pin and outer pin. The inner pin always  is the positive and the outer pin is negative. There is special circuity in the laptop motherboard that prevents power to reach motherboard if it is connected incorrectly. Not in all but in most of the motherboards.

The DC jack is connected to the motherboard usually with 4 pins. One pin usually at the back of the jack solid pin is positive. and other pins including the shield if there is a shield of the jack are negative. This may be not the best design solution but this way designed most of the laptops except Apple and Toshiba and a few other models.

The bad thing about this king of design is  that it is difficult to solder this jack on the motherboard. Because the solid pin needs more heat to solder properly in usually it ends with cold soldering of the pin. And if we take in that the jack also is affected by the forces coming through the power cable as we move the laptop around no wonder DC jack often get loose and even burn out in the motherboards.

The burned place of the DC jack usually look like this and with even damages copper track on the motherboard. The other jack design that is located not on the motherboard also suffers from defects. We saw a DC jack with wires coming off because it became loose in his place and this was caused by loose hinges. But with hinges and the hinge fitting quality and design is another story.

DC jack fixed in two way. If it is not completely burned out on the MB and only the positive pin is lose we connect it wit a wire to the track on the motherboard. If it is completely burned out we desolder it with hot air gun and solder in a new jack.