When I press the power button the laptop doesn't display anything at all, plain dead. power and the drive LEDs turns on but drive LED goes off within 2-3 secs. I tried replacing the hard drive but didn't work. My laptop model is Samsung NP3505C-S06IN. Fan turns on but as well as the drive LED goes off, fan goes off too
Laptop dead...drive LED and fan goes off after 2/3 secs
The first thing I would do is to pull the charger and the battery out from the laptop. Then I would press the power button and wait for about 30 secs. After that I would try to boot my laptop with only the charger plugged in.
My advice to you, if the warranty of your laptop has expired would be to take out the hard drive and try to connect it to another computer through SATA-USB cable. If your hard drive spins up on a different computer and it is recognized there, but cannot power up on your laptop, then the problem is hiding probably in the power supply unit on your motherboard. While on another PC, I advise you to make a backup of your files just in case that you need to replace the motherboard completely.
You could bring your laptop to a technician to make a test of the power connector and/or the power jack center because they might have got damaged.