Question HDD PCB swap mystery

Jul 2, 2020
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Hi all,

First off, I'm new to these forums, so I apologise if this thread is in the wrong place.

A while ago I took my two 500gb Hitachi Deskstar HDDs out of an old PC and was using them externally via a dock when I absentmindedly connected the wrong power supply to the dock and ended up frying the board of one of the hard drives. I only realised my error when I saw the smoke and by then it was too late. However, since the drives were identical, I swapped the boards over and the drive powered up, but my computer then refused to read it. The drive has some non-essential data on it, but my goal is to recover the files on there.

I got a pal of mine to help with soldering and swapped the BIOS chips in the PCBs from one board to the other - the computer then picked up the drive but it had to be activated, initialised, formatted etc. I saved the RAW data and then formatted the drive and now it works, but, as mentioned above, I would like to recover the data from it. Recuva hangs while scanning it and chkdsk is reporting a time of 900 hours to scan and fix bad sectors, tested on both my laptop and my PC. Every other test I've run, (sfc scannow etc.) comes back with no errors. The drive runs fine otherwise - no clicking etc.

Where do I go from here? What's the best path to recovering my data? Is it lost forever? Some sort of physical issue? My best guess is that in swapping the chips over the file tables don't match, but I am not sure how to fix this.

Thanks.

P.S. Images of hard drive attached.
View: https://imgur.com/a/1sFVqCC
 
Last edited:

ex_bubblehead

Champion
Moderator
Unless the replacement board is an EXACT match to the old you are out of luck. Exact match means just that, the boards must be identical in every respect, right down to the component level. Anything else will result in what you are seeing now. In addition, it's entirely possible that connecting the wrong power supply may have blown one or more of the heads. If you really need what's on that drive (why no backups of important data?) then a recovery service will be your only option, and, since you've attempted recovery on your own by partitioning and formatting, it's (extremely) likely that you've created a situation where even the experts won't be able to recover anything usable.
 
Jul 2, 2020
2
0
10
0
Unless the replacement board is an EXACT match to the old you are out of luck. Exact match means just that, the boards must be identical in every respect, right down to the component level. Anything else will result in what you are seeing now. In addition, it's entirely possible that connecting the wrong power supply may have blown one or more of the heads. If you really need what's on that drive (why no backups of important data?) then a recovery service will be your only option, and, since you've attempted recovery on your own by partitioning and formatting, it's (extremely) likely that you've created a situation where even the experts won't be able to recover anything usable.
Hi,

Thanks for your response.

As far as I can tell, the boards were an exact match. As soon as I swapped them, the HDD powered up again. They were two of the same model, make, size, amount of sectors etc., shipped in the same computer, so I doubt they would differ wildly. Take a look at the images I attached, they look identical to me.

If it had blown one of the heads, surely I wouldn't be able to use it as storage - as I am able to do now? (I loaded a few picture files onto it to test.) As for "why no backups" - apart from being an unproductive comment, this is what I was doing while attempting to power up the drive and you'll see that I did backup the RAW data on the drive. I didn't partition the drive, I did a quick format. In the past I have been able to successfully recover data from drives I have quick formatted fairly frequently.

My best guess is that in swapping the BIOS chips over the file indexes are misaligned, but I am not sure how to fix this. I tried to repair the file table but I am not sure if this worked.
 
@leem91, the usual result of an overvoltage is a shorted TVS diode. "LE" is the 12V TVS diode, "AE" is the 5V diode. Were these diodes shorted?

TVS Diode FAQ:
http://www.hddoracle.com/viewtopic.php?f=100&t=86

As you correctly state, the "BIOS" chip ("NVRAM", 93C76WP, location U5) contains unique information which must be transferred from patient to donor. You appear to have done this successfully.

This is a similar PCB:
https://sep.yimg.com/ay/yhst-14437584971410/hdp725050gla360-0a29734-0a53129-0a90026-0a35415-ba2653-oa29734-oa90026-oa53129-3-5-sata-hitachi-circuit-board-fw-1.gif

There is an additional "BIOS" chip ("ROM") at location U7. This location is unpopulated on your PCBs, which means that the ROM code is embedded within your MCU (U1). The ROM code version must match the NVRAM version. Since you were able to format your drive after transferring the NVRAM, it would appear that the donor and patient ROM versions are in fact matched.

What do you mean when you say "I did backup the RAW data on the drive"? Are you saying that you cloned the drive? How were you able to access the data if the OS was seeing the file system as RAW?

BTW, you should NEVER write on a drive whose data you wish to recover. By doing so ("activated, initialised, formatted, repair the file table, etc"), you have needlessly complicated the recovery. Whoever is dumping this "quick format before recovery" nonsense on the Internet is a dangerous fool.

Can you retrieve a SMART report with a tool such as CrystalDiskInfo or GSmartControl? Look for reallocated, pending or uncorrectable sectors.

I would clone your drive with a tool that understands how to work with bad media (HDDSuperClone or ddrescue), and then run data recovery software against the clone. My favourite tool is DMDE (US$20).
 
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