You should firstly check out the adapter' wire. You will find a plug at one end of the adapter and another lead connecting to itself at the other end. Make certain that whether these connections are tight or not. And you also need to check the pins in the socket. If it is damaged, you need to choose for a brand-new one. Besides the wire, you can find out the right malady be the LED adapter light. Most of LED light will illuminate the adapter is working. If you find out that the light isn't working, you need to take it apart to see its internal structure. In addition, you can test an HP AC adapter with a DMM device. And then you can easily see how much current is flowing through the unit.
If the wire of the adapter is broken, you need to find out breaks or frayed areas on the wire. Unplug the laptop in advance, and then you can cut the broken or frayed wire and reconnect it with solder. When you have finished soldering, you need to tape up the cable carefully. Proper insulation is very important, or you will get electric shock at some time. Moreover, you need to choose the solder with the matching color with your adapter's wire.
If you have not found any breakage on the external wire, you can check out the internal wire. If your adapters are assembled by screws, you can simply open it by removing screws. And some adapters are glued together; you need to take it apart with some special tools. It is up to you to open the adapter or not, but you need to do this carefully. You can get high quality laptop adapters at cheap price online, so you can absolutely change the existing adapter for a brand-new one.