Hey guys I have My Book Essential Hdd with ac adaptor thatvgives output 12V 1.5A unfortunately , my friend plugged in alap adapter by accident which gives an output of 19V 4.25A , the Hdd wont start , i want to know if the hdd power is gone ? & can i change apower unit or any hardware to turn it on , since i need data on this hard drive

DIY has its risks, and not advised on drives which have important data.
Take professional help if data is critical to you.

The Bridge board ,SATA to USB, would have failed.
Check for visible faults.
Post a pic to identify common faults.

Connect the drive directly to the SATA Port of a PC and check if its detecting properly in the BIOS.
If it detects properly, then you will need a similar Bridge board (or rectify the original board) to access the data, because of possibility of encryption .(DO NOT format or do any write operations on the drive)

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