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 Post subject: Seagate Barracuda 7200.10 - suspected TVS damage
PostPosted: March 25th, 2017, 11:05 
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Joined: March 25th, 2017, 10:31
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Location: UK
Hello

I've got a 500GB Seagate Barracuda 7200.10 drive which I have accidentally damaged by using the wrong SATA cable with my new modular PSU (grabbed a cable that belonged to the previous PSU!). When I pushed the power button, there was a fat spark and the magic blue smoke escaped from something (looked like the SSD, which is also dead).

From the research I've done online, I suspect the 5V TVS diode has shorted.

  • The PC will not boot with the drive connected (brief flicker of life and then stops)
  • Hot-plugging the drive when the PC is on shuts off the PSU
  • The diode highlighted in red (see attached picture, QE R805) presents a single figure resistance (reading 005 - 008).
  • The same diode presents either no voltage drop or a very small value (0.001 V) in both directions when using the diode test mode.
  • The diode next to it (blue, BUX C749) presents a voltage drop of 0.75 V in one direction and OL in the other. It also presents significant resistance (OL until 20k setting).

I've read a number of articles / posts online suggesting that the TVS diode can be safely removed (for a given value of safe!). I trust the PSU to remain stable (Seasonic M12), but I am aware that there is a risk if the voltage fluctuates.

I've been quoted £150 - 200+ as a guide price for professional recovery. The drive contains many GB of photographs that I would prefer not to lose. The drive has not been inspected but both companies advised that they would likely replace the PCB.

  • Are there any other tests I can do DIY to confirm the problem? Any other components I should check?
  • If I remove the TVS diode, is there any potential to cause damage other than through overvoltage?
  • Is this drive one where I could replace the PCB with an identical one and operate it, or would it need ROM chips etc swapped over?

Many thanks
Ben


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SeagateBarracuda7200.10.jpg [ 3.04 MiB | Viewed 14566 times ]
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 Post subject: Re: Seagate Barracuda 7200.10 - suspected TVS damage
PostPosted: March 25th, 2017, 11:26 
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Joined: October 16th, 2013, 13:21
Posts: 713
Location: Brazil
Get the pinous for the sata power connector, and test continuity between the 5V, 12V and GND pins. You will probably find that the 5V is shorted to GND and (maybe) the 12V not.

That being the case, you can carefully remove the corresponding TVS diode. It would be better if you can get another old hard disk to donate a replacement before connecting the hdd to the power supply.

It is your drive, so it is your decision to risk it and the files in it. **Probably** it is just the TVS, but after removing the TVS, check again the 5,12 and GND pins for continuity between them. If the short you observed before disappeared, chances are the problem was only the TVS. If the short remains, you may have other components damaged.


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 Post subject: Re: Seagate Barracuda 7200.10 - suspected TVS damage
PostPosted: March 25th, 2017, 11:45 
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Joined: March 25th, 2017, 10:31
Posts: 7
Location: UK
Thanks for the quick response! That's really helpful :D

Quote:
Get the pinous for the sata power connector, and test continuity between the 5V, 12V and GND pins. You will probably find that the 5V is shorted to GND and (maybe) the 12V not.


My multimeter does not have a continuity test mode, but I've checked the resistance at the 200 ohm setting and got the following:

  • 3.3V - GND: OL
  • 5V - GND: 0.8
  • 12V - GND: OL

That would seem to agree with what you're saying.

Quote:
It is your drive, so it is your decision to risk it and the files in it.


Absolutely. I would like to understand what the risks (and mitigations) are before deciding whether it's worth just paying for professional recovery.

As I understand it:

  • Overvoltage - can be avoided by replacing the TVS with a donor part. Does this need to be an exact replacement (QE R805) or will any TVS of similar spec be sufficient?
  • Damage to PCB during TVS removal - am I better to de-solder or clip it off?
  • Damage to PCB during TVS replacement - how heat sensitive are the other components? Do I have to be quick and precise to avoid damage?
  • Damage to other components - re-test continuity after removing / replacing TVS to confirm 5V is no longer shorted to GND.
  • Any other risks I should consider?

If I'm going to buy another identical drive for it's TVS diode, am I easier to swap the entire PCB and avoid any risks from soldering etc?


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 Post subject: Re: Seagate Barracuda 7200.10 - suspected TVS damage
PostPosted: March 25th, 2017, 11:49 
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Joined: September 8th, 2009, 18:21
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If you would prefer to replace the PCB, then you can puchase a replacement on eBay for a few dollars. Just make sure the firmware matches yours.

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 Post subject: Re: Seagate Barracuda 7200.10 - suspected TVS damage
PostPosted: March 25th, 2017, 13:52 
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Joined: March 25th, 2017, 10:31
Posts: 7
Location: UK
fzabkar wrote:
If you would prefer to replace the PCB, then you can puchase a replacement on eBay for a few dollars. Just make sure the firmware matches yours.


Thanks. I've ordered an identical (working) HDD on eBay and will pull the PCB from it. It was cheaper to buy a used drive than a PCB - there are no UK sellers listing a compatible PCB, and all international sellers were charging as much for postage as the board itself.

I've removed the TVS diode from the existing board and the 5V line is no longer shorted to GND. I'm going to wait and replace the PCB though, it feels safer since I have no idea what other damage the board might have sustained. I'd be happier to power this board up if I didn't have data on the drive!

Hopefully the drive will work with the new PCB and I'll be able to copy my data off.


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 Post subject: Re: Seagate Barracuda 7200.10 - suspected TVS damage
PostPosted: March 25th, 2017, 14:15 
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Joined: September 8th, 2009, 18:21
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After removing the 5V TVS diode, measure the voltages at V1, V2, and Vneg. If they are OK, then the PCB is most probably working. Do this with the board disconnected from the drive.


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 Post subject: Re: Seagate Barracuda 7200.10 - suspected TVS damage
PostPosted: March 25th, 2017, 14:31 
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Joined: March 25th, 2017, 10:31
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Location: UK
Thanks!

I take it I should supply power via SATA connector from the PSU in the normal way.

Am I measuring the voltage between each of these points and GND, or across the components?

What voltages am I expecting to see for each one?


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 Post subject: Re: Seagate Barracuda 7200.10 - suspected TVS damage
PostPosted: March 25th, 2017, 14:42 
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Joined: September 8th, 2009, 18:21
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Location: Australia
Apply power to the SATA connector, but confirm that the SATA voltages are correct before you do so.

http://pinouts.ru/Power/sata-power_pinout.shtml

Measure the voltages between each test point and ground, eg a screw hole.

I expect that you should see -5V for Vneg, +3.3V for Vio and somewhere in the range of +1V to +2V for Vcore. I'm not sure which of V1 or V2 corresponds to Vio and Vcore, but your measurements will tell us.

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 Post subject: Re: Seagate Barracuda 7200.10 - suspected TVS damage
PostPosted: March 31st, 2017, 17:59 
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Joined: March 25th, 2017, 10:31
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My spare drive arrived today, so I have a PCB with a working TVS diode now.

I tested my original PCB and got the following voltages:

V1 = 1.27
V2 = 3.35
Vneg = -4.91

That seems to match what you predicted. Is there anything else I should check before connecting the drive? I've read about possible pre-amp damage, is there anything I can do to check for that?


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 Post subject: Re: Seagate Barracuda 7200.10 - suspected TVS damage
PostPosted: March 31st, 2017, 18:07 
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Location: Australia
You could install either the patient or donor PCB onto the drive and measure the resistance between ground and each of +5V and Vneg, in the absence of power. This will tell us if either of the preamp's supply voltages are shorted to ground. If there is no short, then you should be OK.

If your donor is a match, then I would use its PCB rather than the patient's.

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 Post subject: Re: Seagate Barracuda 7200.10 - suspected TVS damage
PostPosted: March 31st, 2017, 18:29 
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Joined: March 25th, 2017, 10:31
Posts: 7
Location: UK
Thank you very much - I fitted the donor PCB.

Both the +5V pin on SATA connector and Vneg read infinite resistance to the GND pin on the SATA connector (using 200 ohm setting).

Just out of interest, I fitted the patient PCB to the donor drive and measured with the same results.


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 Post subject: Re: Seagate Barracuda 7200.10 - suspected TVS damage
PostPosted: March 31st, 2017, 18:47 
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Location: Australia
Good luck.

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 Post subject: Re: Seagate Barracuda 7200.10 - suspected TVS damage
PostPosted: April 1st, 2017, 8:35 
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Joined: March 25th, 2017, 10:31
Posts: 7
Location: UK
Success!

Recovered everything - 376GB of data.

I can't thank you enough for all your help. I will certainly be taking much more regular backups from now on.


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