Why wont my laptop charge with a functional power supply? It is the right voltage and everything.?

My laptop was dieing so i plug the power supply into the DC plug and thinking it was charging i keep doing my own thing when my laptop just shuts down as if it didnt charge, i check and notice the light telling me the laptop is being charged isnt on, so i unplug the power supply and replug it gives me green light but when i plug it into my laptop the green light goes off and a beeping sound comes from the PS so i think to myself this PS is a goner and i go out and buy a new one....its a universal PS, i set it to right voltage switch it to the right plug. I plug the powersupply into the wall lights up everything loooks good then i go to plug it into laptop and same think happenes as my last PS light turns off and it makes a beeping sound....which means something is wrong with my laptop. This happen to anyone before or they know whats wrong? The model is Acer Aspire 6920g if it helps.