One is the usual LAPTOP JACK ISSUE. It's so prevalent that you can find businesses on the net that do just this one repair.
We also have dead adapters. But this is usually easy to test. The first test is with the Volt meter. Can't use that test? Replace the adapter and hope.
I have a Gateway nv5378u. Today it suddenly beeped to indicate that AC power had been disconnected, while it was still plugged in. Now it does not recognize that it is plugged in and will run on battery power only. When plugged in, the indicator light on the AC power adapter brick dims, and pulses, but returns to normal when unplugged from the laptop. Is this an adapter, battery, power connection, or motherboard problem? And how do i fix it? I've already done a power reset, and tried a different power outlet.