Hi guys! I´m into the task of getting my mom´s files back from a death HDD. This drive is a Samsung HD502HJ with a PCB version BF41-00352A (on the back, on the front it says F3_1D rev. 05). I have a donor HDD, same model, same PCB numbers in the back and front BUT, they have different electronic components soldered on them. The situatuion is like in this pictures. The damaged one has those in the bottom right and also on the left of the memory chip. I have seen this in other PCB revisions of this model (Rev 01 for example). The question is.... The donor PCB (which works fine) will work in the damaged disk (I´m sure the issue is in the PCB) having these differences despite being exact same PCB model? I plan to do the BIOS IC swap. I know that doing this with a good PCB should work, provided is the same PCB model, but I couldn´t find info about these same PCB models that are not really the same. Also, what does these components do? Seems something optional, at least, I hope so. Thanks!

I wanted to do some more comments regarding the faulty HDD. Before dying, it started to spin up and down and being recognized by Windows sometimes. Files were accessible once it spinned up and worked fine. I thought it was a faulty power connector due to a recent PSU change, but once I took it out from my mom´s PC I couldn´t make it work in another PC in order to do the backup. The drive does nothing, not even gets hot, chips are, at most, warm but definitelly not hot. There is no obvious visual damage, and the 12V and 5V TVS diodes seem fine, also the 0 ohm resistor. (I have been reading and learning from other posts before posting). So far I found that there is no -5V where it should be, I think I meassured 0,2V there. 18V is not there either, 10v or 12v, i don´t remember exactly, I´ll come back with more precise meassurements if you think it´s woth to find the culprit. Asso the HDD spins up if a change the PCB, it just not get recognized at boot (no BIOS swap yet) Thanks again!

Those extra components are shock sensors and operational amplifiers. I haven't yet heard of any case where a difference in this area has resulted in an incompatibility issue.

It's a Seagate drive, and it's a different sensor, but here is a case where the firmware update for the AS (no G-sensor) and ASG (G-sensor) versions of a particular model are byte-for-byte identical.

https://web.archive.org/web/20230731131249/http://www.users.on.net/~fzabkar/Dell_AS_ASG_FW.jpg

Therefore, I expect that the firmware would be able to autodetect the presence of these sensors and make appropriate adjustments.

I could be wrong, though.

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A backup a day keeps DR away.

Thanks fzabkar. I knew you will answer, I also added info about the faulty drive but that post vanished. I´ll come back to check if it shows up and we can continue discussing the issue with that one. Thanks again!

Does the drive still spin up with the original PCB? If so, then the problem is most likely internal, not PCB related.

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A backup a day keeps DR away.

No, it does nothing. It does spin up with the new PCB, just it doesn´t get recognized by BIOS. Chips dont even get hot, warm at most and there is no visible or obvious damage. What I have found by comparing good drive vs bad, and also a good Rev 1 I have, (also reading other posts with your contributions) is that there is no -5V (where it should be) nor the 18V next to the motor IC. TVS diodes seem fine, 0 ohm resistor looks good too. I made a more detailed explanation about what happened but like i said before, that post vanished. I´ll come back with more detailed meassurements. Thanks.

I took notes on the picture while I was measuring, so, to be clear:
north 4R7 coil measurement points: 1,02 V
south 4R7: 2,55 V
Bottom right capacitors of the MCU ( meassured to the right of both): top 11 V (should be 18 V right?)
bottom 11,6 V (should be 12 V no?)

The anode of the diode adjacent to the 2R2 coil: 0,2V (should be -5 V?)

I think 18V may not be present until the motor is spinning. The -5V supply probably needs to be switched on by the MCU.

I believe this is one of those models that may be affected by FIPS errors in the ROM. This will result in a no-spin symptom.

You can use a USB-TTL serial adaptor to capture the diagnostic messages from the UART port.

How to connect a terminal adaptor on a Samsung drive ?
https://www.hddoracle.com/viewtopic.php?f=116&t=189

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A backup a day keeps DR away.

Thanks fzakbar. So if a make the IC BIOS swap it wouldn´t work, I´ll be carrying the FIPS error with it.

Yes. A FIPS error can be repaired, though.

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A backup a day keeps DR away.

Thanks fzabkar. A friend of mine has one of those USB-TTL adapters. I did some research and his adapter uses a CH340 chip (5v and 3,3V), also I can buy one with the Pl2303 (5v and 3,3V too). Which one is better for this task? Also, PUTTY will be enough or I need a more advanced tool?

The I/O voltage for your PCB appears to be 2.5V. Therefore it would be better to find an adapter with a selectable voltage -- 1.8V/2.5V/3.3V.

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A backup a day keeps DR away.

Hi fzabkar. While waiting for the new adapater, I was wondering if the BIOS could be in a fail-safe state that I have to reset. The way the disk failed is what makes me think that. It started right after a power supply change and the disk spinned up and down getting detected intermittently. I´m not familiar with all this and the FIPS error, I don´t know if that is a clear symptong of a power issue or the error mentioned.

I don't know the reason, but there is a small section in the ROM that sometimes becomes corrupt. This section has a "FIPS" header.

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A backup a day keeps DR away.