If it's out of warranty drop a line to ikenfixit.com and notefix.com Both have done board level repairs of the power supply area.
However if you have many year old batteries be sure to ask to send them in for a test since an old battery can overtax the charging circuit and cause a failure. It's been tough to get people to stop slipping in that old battery. They hope it will come back but it is more likely to damage the circuits.
My HP zd8000 notebook will not turn on. Not even one iota of noise or activity when I press the power button. Initially, the AC power adapter failed (the green LED on the power adapter did not come on). So I purchased a new HP replacement power adapter and verified that the green LED came on. When I connected it to my notebook, it would not turn on. I noted that the AC power light is on. Also, the battery light is on, however, it is blinking (which states that the battery has a low charge). Therefore, I assume the battery is not charging.
I followed instructions per HP troubleshooting article "HP Notebook PCs - Notebook Does Not Startup or Boot Displaying a Blank Screen". I re-seated the RAM, as instructed, and the notebook still does not turn
on. I corresponded with HP tech support. Aside from re-seating the RAM, they stated to re-seat the hard drive. I did this but to no avail. They said to send it in?of course, I can buy a new laptop for the price they will charge for diagnostic and repair!
Please note that when the AC power adapter initially failed, I had a spare battery (which had a charge) and continued using the notebook while waiting for the new AC power adapter to arrive until the battery died. Therefore, I can conclude that the notebook is operational but it cannot receive AC power to charge the battery.
Please advise. Thanks.