hp z5000 Power Supply problem

Light charging indicator keeps going off and on and at some point I would run out of battery power, I bought a new power supply and had the same problem, I read some threads and following some advice I replaced the DC JaCK, still the power goes off and on, I can make it go on by Unplugging the power supply and plugging it back in it charges for (2) seconds and it goes off again, I cant keep doing this, What else can it be? Im now at a loss , Please someone Help.
Thanks