The first thing to check is the output of your AC adapter. you should get DC19.5V 4.62A. If that works, you need to disassemble your laptop and check the DC jack. Your model uses a DC jack that plugs into the logic board. Check the wires and the connector to make sure it is properly seated and that the pins are in good working order. You can get the service manual [http://support.dell.com/support/edocs/systems/studio1555/en/sm/index.htm|from here]. It will show you how to work on your laptop. Hope this helps, good luck.