I'm working on a Studio 1558 that was not charging.  I first installed a new power port inside the laptop.  When I connected the AC adapter to the new port, the light on the port would briefly come on then go off again.  At no point could I make it stay on continuously.  I also tried this with the old port, and got the same thing.  (Obviously, this is not a port issue.)

The specs on this genuine Dell adapter are 65W 19.5V 3.34A.  When I searched on the Dell site for a new adapter for this model laptop, the specs were supposed to be 90W 19.5V 4.52A.  

I ordered this new adapter but unfortunately, when I plug it in, the light on the power port does the exact same thing.  It flashes on very briefly.

Can anyone tell me what the problem is with this machine?
Thank you.