Hi,
Does your tab perform correctly if you have it connected to the charger and the charger is switched ON?
If not can you try another charger? If the new one works your old charger is faulty. Allow the new charger to charge the battery and then see how it works on battery alone.
If it does work on your old charger, then you either have a faulty battery or a faulty charging circuit in your tab.
If this is the case suggest you check your warranty and if still valid contact the manufacturer.
Here is a link to the service manual if you are interested.
http://h10032.www1.hp.com/ctg/Manual/c04495010.pdf