Hello all
I am new here and found this page while hunting for an answer. Hoping you all can point me in the right direction.
The issue:
Business surveillance DVR no longer accepts internal HDD. HDD is a 4tb Seagate ST4000VX016
When DVR powered on the system just beeps indicating a hard drive issue. HDD does not spin, click, gyro, or make any noises. When I disconnect the drive from DVR, DVR main menu pops up.

What I've done thus far:
Purchased a donor HDD with the same PCB numbers. I have switched the BIOS chip from source drive to donor PCB and reinstalled modified PCB.
The DVR no longer beeps, initialized, and allowed menu access. However when searching for events DVR says there is no DATA.

Am I missing something? Should I copy the BIOS with a BIOS chip reader and just flash the donor PCB?

I'll try to include PCB pics and BIOS chip pics

Thanks for any direction

Perhaps there is a unique encryption key in the MCU ???

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A backup a day keeps DR away.

I connected it to a write blocker and I would think I would still see 1s and 0s and encrypted binary, correct? Maybe?

DVR drives often have customised firmware. I would try to repair the original PCB, or at least narrow down the faulty component. You wouldn't need to reinstall the original ROM to perform some basic measurements.

_________________
A backup a day keeps DR away.

Test points.


DMP2040USS, Diodes Inc, P-ch Enhancement Mode MOSFET, -20V, -7A, 33mOhm Rdson, marking P2040US, SO-8:
https://www.diodes.com/assets/Datasheets/DMP2040USS.pdf

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A backup a day keeps DR away.

Funny enough before you posted this. I was testing the 12v lines and they were grounding out. Whent down the line and found one of the diodes is shorted. Compared to the donor board that was providing good forward and reverse basis. I should be able to remove this diode and replace from donor or leave off?

You can remove the 12V TVS diode. The drive will work without it, albeit without overvoltage protection. Also check the zero-ohm resistors near the shock sensor and DMP2040USS MOSFET.

_________________
A backup a day keeps DR away.

I fixed it! 12v diode removed, I did replace with donor diode. I switched the bios back and it booted up with all data intact. Thanks for your help and walking me through this