external drive was connected to a 20v notebook charger.
s/n 9vp5p01b Firmware CC44 on PCP: 100535537 REV A (back) seagate 2A94V-0 (front)

i measured no resistance along the 12v lane until behind the black diode(?)
unlike the 5v lane where the black unit on it is has about 30 kOhm in both direction

what else may i measure, replace or bypass? (stable powersource present)
thanks:)

The USB bridge board would be dead, so get rid of that, just hook the drive to your computer to get files off, but you might have blown the 12V Zero ohm resisters and a shorted 12V diod that you will need to fix. on the HDD pcb. I suspect the 5V connection will be okay on the HDD.

I would not get rid of any usb board until files are safely off. Sometimes you will need the old one, and better to be safe than sorry.

If it was a Western Digital drive then yes as it will use encryption, but Seagate drives should not. But its always good to keep the bridge board as HaQue says... just in case. When I said get rid of it I meant put it in a box and don't worry about it.

usb board works still unfortunately(intenso case without encryption) thats why i removed the pcb.
i saw people bypassed some of the first units on the 12v lane on this pcb type after they burned. Yet having no resitance already bypassing wouldnt possibly help?

As said 1. What units can i possibly measure or bypass or exchange? 2.to exchange whole pcb, i need to exchange what chips if any? Thanks:)

(USB is only on the picture just in case it helps guessing what may happen to the hdd power input/killed the hdd)

Remove the 12V TVS diode with flush cutters. In most cases that's the only problem. Just be sure not to overvolt your drive again. Retest the resistance after removing the diode to confirm that no short circuit remains. There appear to be several inductors to the left of the diode. Hopefully these have not burnt.

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