Hi there

I have a Seagate Barracuda 500GB (Firmware KC45) 3.5" HDD. I was using it on my PC and took it out to do a backup and I very much regret doing this

I connected the HDD to USB 2.0 to SATA adapter and didn't notice that the adapter was already plugged into the power outlet. While plugging the power from the adapter to the HDD, I believe a power surge occurred which in turn fried the board I guess because I could smell something burning. I quickly took out the power but it was too late. I had killed my HDD with all my data. Put it back to my PC and even the adapter but HDD couldn't power on. I suspected the board had been fried so I changed the board with another Seagate Barracuda 500GB HDD with the same firmware (Firmware KC45) and model number (ST500DM002). Infact I bought these two HDDs the very same day from the very same supplier. Most of the details of these two HDDs are same except for the "Site Code" which I believe is the place where product was manufactured. The one with the fried board is made in China and the working one is made in Thailand.

Once I changed board, HDD came on again (can hear it spinning) so I connect it back to my PC using the USB to SATA adapter. Nothing comes up in my computer so I go to Disk Management under Computer Management. As soon as I went to Disk Management, I got a prompt "You must initialize a disk before Logical Disk Manager can access it". This was the disk that I had just plugged in and it was giving me two options for Partition Style: MBR and GPT. Initially I cancelled this but I noticed that Disk Management shows my disk as Unknown, Not Initialized and was only 3.86GB instead of 500GB !!!

So I took the disk off and connected it again and this time when the "Initialize Disk" prompt came up, I chose MBR and clicked on OK and I get "Data error (cyclic redundancy check).

I tried few of the partition recovery software (DiskInternals Partition Recovery, R-Studio, EaseUS Partition Recovery, MiniTool Partition Wizard Home Edition, TestDisk) but all of them were showing my disk size as 3.86 GB except for TestDisk which wasn't even detecting my disk.

Can someone please help me out. I've lost alot of important data

Your computer is not detecting the drive but only pcb informations.
The reason is that the pcb swap is not enough for this type of drive, you need to swap also the rom from native pcb to the good pcb.

To do this you need an eprom programmer, if you don't have it i can do this job for you but you have to ship the drive to Italy.
Where are you from?

P.S.
Also, it might be possible to repair the native pcb, if you are able to fix it you will not need any rom swap.
Check about "TVS diode" on this forum

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My firmware database:
https://mega.nz/folder/O01DkBRI

I suspect that there will be burnt inductors in addition to a shorted TVS diode. You can repair the board by removing the shorted diode and bridging the inductors.

See http://hddrepairing.com/downloads_n_vid ... airing.pdf

http://www.users.on.net/~fzabkar/HDD/TVS_diode_FAQ.html
http://www.users.on.net/~fzabkar/HDD/ (photo clips)

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A backup a day keeps DR away.

I have the same Barracuda 500GB same firmware. It Works when connected directly to SATA or eSATA, but it doesn't work correctly connected to an USB port 2.0 or 3.0 (Using StarTech.com HDD dock station). I will try another SATA to USB bridge.