Why is printer still not coming on after replacing power adapter?
4630 Printer does not power on
If you have replaced the power adapter as in the cable the plugs into an outlet check to ensure that the cable is the correct voltage for the printer. HP is pretty good about putting the required voltage on a sticker near the DC plug of the printer
If the cable is correct check to see if there are any LCD indicators illuminating on the printer after you press the power button. If there is still no power, this may be the power supply which is underneath the LCD screen. If you haven't already replaced this part, this would be the starting point. Since the power supply is what circulates power throughout the printer.
Your printer may be under a warranty to have the printer replaced so check to see if you do on HP's website