Hi everyone, I need help on this model.When it came there was lack of 19v and I realised Q533 and Q4 were shorted. I replaced and 19v appeared, together with 3.3v and 5v.When I powered on, lights came briefly and went off. then I realised that Q4 shorted(again),Q3,and EC1001. I replaced Q4,Q3,and EC1001(with 4x330uf).
Now, when I power on pc without CPU,all voltages are intact and the laptop stays on, but the moment I insert the CPU, the laptop powers on fully and screen lights up and gets to the 'No Operating System' prompt, then the laptop goes off and when I check, Q4 and sometimes Q4 and Q3 are shorted. I have replaced U501(TPS51260) and CPU but the problem still remains. Any help will be appreciated.

Well I had help from a different forum to check components from VBSTx pins of TPS51620 , I remember caps C552,C553,C534 were chipped off from the motherboard when it came in... so I decided to check today and found out that there was a dry joint between C534 and R522. Problem has been solved..