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 Post subject: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 21st, 2021, 10:18 
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Joined: June 21st, 2021, 10:07
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Location: UK - yorkshire
Hi,
My Dad is building a PC and he plugged in 4 x 14TB WD HD's. The PC had already been booted using an SSD which has the OS.
The HD's didn't show in BIOS or on boot so I had a look for him even though I am no expert at computers.
You can see the drive in disk management but it will not make a partition table etc. – ‘The request failed due to a fatal device error.’
First thing I found was that the drives didn’t feel like they were spinning. I checked the power connections and found that the 6 pin to SATA he used was NOT from the Corsair Power kit! Someone much have swapped a connector and returned it or something as the connectors are clearly different to the others.
As I said I no expert on PCs or HD’s to the level of advice offered on this forum, but would I right in saying this might have reversed polarity? And does this mean the end? :shock:
Thank you for you time.


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 Post subject: Re: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 21st, 2021, 10:53 
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Modular PSU's a gift that keeps giving - https://forum.hddguru.com/viewtopic.php?f=1&t=41389

You may be lucky and need just need to clip/replace the diode or you may be unlucky. WD protection is better than others according to those who understand.

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 Post subject: Re: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 21st, 2021, 11:28 
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Thanks you so much for the reply. I will buy a small torx set and look tomorrow.

The HDs are the ones you linked so i think the image at the bottom must be be the underside.


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 Post subject: Re: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 21st, 2021, 11:38 
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If you don't have one grab a cheap multimeter too (just a beer money one), to test the diodes and the fuses.

Test with one drive first and BEFORE applying power again especially if you clip the diode, make sure you have the correct power cables.

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 Post subject: Re: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 21st, 2021, 15:46 
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TVS Diode FAQ:
http://www.hddoracle.com/viewtopic.php?f=100&t=86

Since the HDDs do not shut down the PSU, I suspect that one of the fuses must be open circuit.

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 Post subject: Re: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 22nd, 2021, 12:15 
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Joined: June 21st, 2021, 10:07
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I opened today but looking at the diodes everything looks OK which I am guessing is not a good thing?

I have attached some images, if someone could check it would be much appreciated. I am not sure really what I am looking at.

Thank you


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 Post subject: Re: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 22nd, 2021, 12:51 
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Unless something went really wrong you're not going to visually see anything. You need a multimeter to check the diodes and resistors/fuses bottom left. Meter in continuity/diode mode and a probe on each side of each component.

fzabkar suggests that one of the fuses is blown, I'd be looking at the one on the 5v rail first.

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 Post subject: Re: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 22nd, 2021, 13:05 
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I have just tried testing everything with a mulitmeter. Again I dont really know what I am doing but I guessed I would try both red/black on either side of anything that looks like a diode.

The tiny one i have marked in red does not appear to be sending anything. The other tiny one to the right of it does (as you look on this pic).

The purple ones also did nothing but i dont know if they are meant to?


EDIT - just seen your reply. Thanks. So the one I marked in red is suspect?


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 Post subject: Re: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 22nd, 2021, 13:16 
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Ignore the purple.
It there's no continuity on the red one - you have probably found your problem :D

Unlike the TVS diodes you can't just clip it off, you will either need to replace it or bridge it, how good is your soldering ?

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 Post subject: Re: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 22nd, 2021, 13:25 
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Excitement turning to apprehension brother.

Excited we might have found the issue, but not too sure on my soldering! The last time I soldered I was in school and I picked it up like a pencil and then cried for a few hours :lol:

How much can I get wrong by having a go :?


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 Post subject: Re: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 22nd, 2021, 13:27 
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Do I need like a little wire over or something, or just cover it in a blob of solder!


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 Post subject: Re: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 22nd, 2021, 13:48 
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You should also check the diodes on the rail (they're just above) - they should have continuity only in one direction just in case it's more than just the fuse.

What you do now really does depend on what you want to do with the drives afterwards. If you're just recovering data in an emergency a solder blob would do. If you want to put them back into service you really should replace it with a new fuse (I think from a quick google that it's a 2A SMD fast blow littlefuse) I'm sure someone will confirm this and the smd size.

These aren't easy components to work with and Id do it under a microscope with a hot air rework station.

Best not to get it wrong :wink: Do you have a friendly local phone repair shop - they'll probably do it for beer tokens.

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 Post subject: Re: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 22nd, 2021, 14:26 
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This isn't an emergency in the sense of lost data - only £1000 worth of new HD's my Dad was going to use in a new build. As such it is defo. worth the money I guess to get the fuse replaced.

I will see if anyone can confirm the '2A SMD fast blow littlelfuse' and then I will make a call to some repair places and get some prices.

Thank you so much again for your help Lardman.


Attachments:
File comment: [quote="Lardman"]You should also check the diodes on the rail (they're just above) - they should have continuity only in one direction just in case it's more than just the fuse. [/quote]

Is this the rail?

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 Post subject: Re: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 22nd, 2021, 15:01 
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The TVS is just above the fuse.
Attachment:
wd14_TVS.PNG
wd14_TVS.PNG [ 300.91 KiB | Viewed 3372 times ]
This is the diode to check, hopefully though it's just the fuse.
It's not financially viable (or sensible ) for most of us to offer a board only service.

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 Post subject: Re: WD 14tb Hard Drives - Reversed Polarity?
PostPosted: June 22nd, 2021, 15:36 
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You can flow a blob of solder over the fuse, if that is the only problem. It reduces the protection, but it's probably something that you would be capable of.

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