I have a Dell M6400 laptop. Up till yesterday, it functioned perfectly. Yesterday morning, I noticed that I was running on plug in power adapter. But today, when I got home, It was turned off, I check the power and it was plugged in. I unplugged the power adapter for 30 seconds and replugged back in, the green light was on and I checked the laptop and it showed charging, but hear some buzzer noise that came out from the power adapter. After plugging in about 5 minutes, the green light on the power adapter was off and it showed no charging. If I unplug and replug it will be working for another five minutes again. I don't know what's going on, if anyone know how to fix this problem, please help. Look like the capacitor inside the power adapter is not working well.