Hi All!

A colleague of mine came to me with a dead 2TB USB external HDD a couple of weeks ago - Naturally, it was choc full of absolutely irreplaceable data, not backed up elsewhere... I'm no data recovery expert, but as a sysadmin I'm expected to work miracles with all electrical goods in the department

Anyways, I stripped the HDD out of the USB enclosure (a Samsung HD204UI), and popped it into a PC I had on the bench - disk didn't spin up, not detected in the BIOS. After a lot of poking about with a multimeter I concluded that the PCB was dead, and that there was a reasonable chance that a replacement PCB swap would get the drive going again (PCB serial No is BF41-00314A).

After furnishing my colleague with my findings and the number of the PCB, he decided it was worthwhile and procured a second hand one from Hong Kong (his decision, not mine...) The board arrived today, nothing outwardly wrong with it, more or less identical as fas as I could tell. I fitted it to the HDD, and sure enough, no spin up and not detected in the BIOS. Great.

Removed the board, and out with the multimeter again. This board has a few more signs of life than the old one; the only thing I can find wrong with it is that the Vneg isn't present. Does anyone know what could cause this, and if it's possible to fix it? Any help is greatly appreciated.

Hi! Thanks for your reply. The data is "irreplaceable", but the guy isn't really interested in spending any more money in getting it recovered - go figure! I think he's pretty much given it up for lost, but if he can get it back cheaply then so much the better.

The drive doesn't spin up with either the new PCB or the old one, so I've not been able to listen for the usual clicking sounds that accompany failed drives.

I don't have an eeprom programmer, and I've made no move to swap over the ROM chip yet.

The native PCB did not have any shorts on it, when plugged into the PC it started normally. There was no voltage present at any of the points in the pic I attached on the leading post, leading me to think it was dead. Removal of the TVS diodes on the native board didn't improve the situation, and the 0 ohm resistor was not blown.

Any thoughts on the lack of V neg on the donor board?

Thanks,

Chris.

@chrisund123, was there any damage to the TVS diodes on the patient PCB?

What resistance do you measure between ground and Vneg when the donor PCB is installed on the drive?

_________________
A backup a day keeps DR away.

Thanks for the replies.

I dont recall there being damage to the patient tvs diodes, but I de-soldered them anyway in a "poke and hope" kinda way... I'll check them again on monday when I'm back at work.

I suspect the donor board is faulty personally. I did a little more poking about while my post was waiting for moderation, and I found that the diode where I was hoping to find Vneg seems to be shorted out on the donor board, but good on the patient board. Reckon I should try swapping them over?

Thanks for your help so far.

Did you measure the diode while the board was on the drive? If so, then a shorted preamp (on the headstack) would produce the same result.

_________________
A backup a day keeps DR away.

Happy to check it out here if you send it to me.

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Nope, I've removed the board from the drive for testing.

That's interesting. Assuming that it's not the capacitor that is shorted, then I wonder what killed the diode. You might like to place the patient board on the drive and perform the same resistance test, just to be certain that a bad preamp hasn't killed your donor. Otherwise I'd swap the diode and hope for the best. Test the board off the drive before trying it, though.

BTW, you may still find that the donor PCB could be incompatible, depending on the firmware version, but at least it should spin up the drive.

_________________
A backup a day keeps DR away.

Hi all!

Thanks very much for all your previous help. I relayed all my findings to the guy I was helping out, and he went back to the supplier of the PCB, who shipped out a replacement.

I hooked up the board to a PC and turned it on, and the correct voltages were present at the suitable points, so I attached it to the drive. The drive now spins up, but it's not detected in the BIOS and it had a lovely clicking sound... I'm pretty certain this means it's out of the hands of an enthusiastic amateur like myself, as the only thing I've not done is swap the ROM chip over from the original PCB to the donor.

Any thoughts?

Do not power it up again and send it to a data recovery professional if you need the data.
Clicking is not good.

Yep that was my thinking!

Thanks for all your help guys.