Hi Dropped my hard drive with power on and it stopped working,so i opened it up plugged in with desktop with power from destop itself and i saw magical smoke coming out of PCB.
Can any one tell how i can replace this PCB and get hard drive working.
attached are Images of burnt PCb and hard drive

PCB defect probably will be the top of the iceberg. The chance to have motor jam is huge.
Replacing of PCB must be done with same number PCB, and you should move ROM from old PCB to new one.
I cross my fingers that the motor is OK.
But if no you should better send it to DR company, it is not DIY job.

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DataRecovery.bg

replacing a ROM ,I don't think so my soldering is good enough for that,Can't just replacing PCB will solve the issue??
OR
Any other way to get it working or at least recover data from it

These before and after photos are for a similar board:

http://www.users.on.net/~fzabkar/HDD/ST ... AS_TVS.jpg
http://www.users.on.net/~fzabkar/HDD/ST ... AS_fix.jpg

Your drive appears to have suffered an overvoltage on the +12V supply. The fix is to remove the shorted 12V TVS diode with flush cutters and then solder a wire from the +12V pins at the SATA connector to the diode's +12V pad on the PCB. However, after doing this you will no longer have overvoltage protection on the +12V supply, so be sure your power supply is good. If you wish to replace the diode, you can use an SMBJ12A. I can't advise you where to get one at Sim Lim, but RS Components should have it, or maybe GEIC at Jalan Besar Plaza.

Before removing the diode, use a digital multimeter to confirm that it is shorted. The only other cause I can think of for the burnt inductors is a possible overload at the motor.

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A backup a day keeps DR away.

yeah you are right its the 12v diode which has gone bad,I am still not sure weather the track on PCB is OK or not,Its burned and i can see copper strip coming out may be i will solder a small jumper from back side...How abt that ??? or i was thinking to go simlim square where someone can repair it for me and also repalce diode.

I can fix the diode for ya, but can't say for sure if it'll fix your hdd. Check your PM for details.