Ok here goes. the charger must supply at least 5.3 volts dc in order for the tablet to show that it is charging properly. The higher the current rating the better but the voltage is what tells the tablet that it has a proper supply. That's all there is to it. Try to use a charger that supplies at least 2 Amps or 2000 miliamps. If yours is 1700 miliamps or 1.7 amps then that's ok too. The higher the current the faster it will charge. If the voltage is not at least 5.3v then the tablet will throttle charging at about .5 amps (500ma) which will take forever and show a red X on the battery icon. The charger does not need to be samsung but samsung makes their chargers run at 5.3 volts on purpose. If you have a samsung charger and your tablet still shows a red x then the charger is faulty by not supplying the required 5.3v. Google 5.3v 2 amp charger to find a suitable one. I hope this helps. Cheers!
btw.. usb ports on laptops and other types of computers are regulated at 5.0v. Which means that your tablet will charge but show a red x and charged at a much lower rate. Some chargers are unregulated which means they do not supply the same voltage. Even if they are made by the same people. they could be 5.0v, 5.1v, 4.9v etc.. the tablet needs to see 5.3v minimum before it will use all available current from the charger.
If your tablet is dead and switches between a battery and blank screen periodically then all is ok. all you need to do is plug in the charger for 10 seconds and unplug. repeat this about 20 times. What you are doing is supplying the full current of the charger before the tablet cuts current to a 'safe minimum'. this is sort of a boost charge to get things going. Once this is done the tablet will begin to charge normally (if the charger is not 5.3v then charging will resume with red x).