Inspiron 15r SE (7520) does not boot

The laptop was operating as normal and suddenly it shut down.

I had bought it on Sep 2012, so it's out of warranty.

When the charger is connected its light is off. If I disconnect it from the laptop it goes on again and as soon as I connect it, it goes off again.

I found several posts which were saying about removing battery-hdd-ram and the power cord and holding the power button for several seconds. I tried these steps but no luck.

Is there anything else that I could do? Is there any chance that my dc power jack is the cause of the prob? Or it is the motherboard's problem?