It work fine with the battery but cannot work with the ac adaptor anymore which use not to be the case a day ago. And my problem is that my battery is dead so I only use to power on the computer using ac adapter but it has suddenly stopped working . No light at all on the computer when you plug in the adapter even though the adapter appears to be fine
How do you know the adapter is OK? If there is no light by the connector when you plug in the charger either the charge is bad or the laptop is bad. If the laptop is bad, a common problem is the power connector itself. Here's what I would do:
Plug in the charger to the laptop and gently press the connector sideways in several different directions. Hold the pressure for several seconds and see if the charge light comes on. If it does, either the plug on the charger or the jack in the computer is worn out.
Try to borrow a charger that is compatible with your machine and try it. See if that fixes it.
If it still doesn't work, time to take the machine to a repair shop.