2 HDD's were pretending to be not there at a hazey time at 7am yesterday. The cables from the pc go through a wall to a work area, so I travelled back and forth 5-7 times fiddling with BIOS and PC connectors, doing advanced yoga positions of crouching and balancing, and I got confused, because, I plugged back the molex of the Y connector of two drives while the PC was running... I touched the 12v pin to the 5v, and my pcb is fried. The pc problem was probably a USB flash drive that makes drives dissapear to bios when it's plugged in.

Theoretically, it is an extremely difficult PCB to replace, as the BIOS is integrated into the marvell controller.
I hope i recover the seagate drive because this one is totally zapped? i feel very silly indeed, for frying 2 drives.

i happened to me once before when some lightning struck the metal stairs next to the pc room, it sounded like a car hit the wall, and 2 days later the power supply died and took a couple of hard drives with it.

What can i do?

Used proper Data Recovery service.

Well you clearly need a replacement pcb as the motor controller chip is burnt out!

You are correct in noticing there is no rom chip on your pcb so the rom info is in the internal flash. You will have to find a pcb supplier who can adapt the replacement and who has the capability to do that from the burnt out donor board or is capable to rebuild the rom info from the drive firmware.

Unfortunately there is another potential problem. The preamp inside the drive might now be damaged. This means the drive has to be opened and the heads have to be changed. I think there is a 50% chance of this happening.

This case is nothing for me if you want to do it for your self you need Donor with same Date code if you find this no need to work on ROM. If not you have to work with ROM... your first task should be correction of PCB problem.

There is much things missing in your experience may be you started work on new hdd's and have no clue about old technology. I don't want to share everything here... but that's good you don't know about this.

Thanks everyone, it's nice to know that there is someone here to help if i have to send the hdd out for pcb refitting.

Yes one of the smd chips is destroyed. The spark lasted a fraction of a second, until a TVS chip must have shorted and sent the PSU to sleep.

Indeed a technical description of the possible repair paths is very welcome.

What is the likelihood of the damage being only the PCB, if i put 12v in the pcb for 1/10th of a second?

This is a fun repair theory battle may the force be with you.

Can you accept a same challenge from me? I think you will run away...

i will pay you $250 USD. If you can't fix it you will pay me $2000 USD, OK ?