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 Post subject: External drive dead due to improper powering
PostPosted: January 29th, 2022, 12:05 
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Joined: January 29th, 2022, 11:20
Posts: 2
Location: Italy
Hello,
I recently did a probably dumb mistake and killed a WD RED 8 TB only 6 months old. I don't care about data inside but I would like learn something from this pricey mistake and maybe gaining some knowledge trying to repair the drive. Thanks in advance for your time and patience.

In 2008 I ran for years an external drive (usb 2.0) by powering it from the 12V of a 4 pin molex of the pc ATX PSU. Fast forward 14 years and I thought to do the same thing, this time using the output of the 12V VGA PCI-e cable on the PSU.

I prepared the connector and double checked it for shorts and correct polarity.

When I connected it to the external drive and as soon as I inserted the plug, pc shutted down immediately like if I had triggered psu protection circuits.
Considering polarity was correct, I though it was the inrush current of the external drive (even the wall brick makes a spark when connecting the drive) so I restarted the pc with the plug inserted (very dumb idea). After few seconds there was clearly a smell of burnt electronics and I immediately shut down everything. The pc now won't start, I suspect of a dead motherboard.
PSU is an evga supernova G3 550W and looks perfectly working.
Motherboard is an Asus P7H57D-V EVO.
The smell of burnt electronics comes from the usb 3.0 ports on the motheboard (that has no sign of burnt chips) and from the SATA to usb PCB of the external drive (who also has no sign a burn chips).
The HDD connected to this PCB was a WD80EFAX-68KNBN0 air filled drive. Now it doesn't spin up even when connected by SATA. Another external drive that was connected (but unpowered) to the usb 3.0 of the motherboard has now the SATA USB converter not working, but I shucked the box and extracted the disk and it seems to be safe and sound.

Can anybody explain to me why powering external drives this way is bad and why in the past worked without issues? I think I created some kind of loop between the 12V line and the 5V line of the usb, but I always thought they referred to the same ground of the PSU.

Considering the drive, would a PCB replacement fix my drive or may I have killed something inside? I found the correct replacement PCB on AliExpress and I have good soldering skills but not for smd components, so transfering the bios chip is a bit scary to me

Thanks to everybody who will have some time to dedicate to me, I really appreciate it


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 Post subject: Re: External drive dead due to improper powering
PostPosted: January 29th, 2022, 19:34 
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Joined: October 3rd, 2005, 0:40
Posts: 3878
Location: Hungary
I can't see a problem with the method if it is done properly, 12V is 12V, GND is the same on the USB and the supply cable, so i think there must be some other mistake. Given the situation i would test every component separately, ie, the external drive with its own PSU, the PC PSU on its own and the mobo with a different PSU, but first find out what's responsible for the smoke...

pepe

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 Post subject: Re: External drive dead due to improper powering
PostPosted: January 29th, 2022, 19:59 
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Joined: September 8th, 2009, 18:21
Posts: 14030
Location: Australia
I wonder if the OP swapped cables between different modular PSUs?

Warning: do not interchange modular PSU cables:
http://www.hddoracle.com/viewtopic.php?f=56&t=2545

It might be worth confirming the pinout:
https://allpinouts.org/pinouts/connectors/power_supply/pci-express-pcie-8pin-power/

The damage to the HDD may be confined to the protection components, in which case there may be a simple, no cost, DIY fix.

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

PCB Protection devices - electronic fuse:
http://www.hddoracle.com/viewtopic.php?f=100&t=1615&p=8872#p8872

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 Post subject: Re: External drive dead due to improper powering
PostPosted: January 29th, 2022, 21:05 
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Joined: January 29th, 2022, 11:20
Posts: 2
Location: Italy
fzabkar wrote:
I wonder if the OP swapped cables between different modular PSUs?

Warning: do not interchange modular PSU cables:
http://www.hddoracle.com/viewtopic.php?f=56&t=2545

It might be worth confirming the pinout:
https://allpinouts.org/pinouts/connectors/power_supply/pci-express-pcie-8pin-power/


I used the original cable that came with the PSU. Before plugging the connector to the external hard drive i doubly checked the value and the polarity with a DMM: it showed +12.2V center positive like the original PSU, so I thought I was ok

fzabkar wrote:

The damage to the HDD may be confined to the protection components, in which case there may be a simple, no cost, DIY fix.

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

PCB Protection devices - electronic fuse:
http://www.hddoracle.com/viewtopic.php?f=100&t=1615&p=8872#p8872


If this is the case it would be amazing, tomorrow I'll study this stuff, thank you!

pepe wrote:
Given the situation i would test every component separately, ie, the external drive with its own PSU, the PC PSU on its own and the mobo with a different PSU


PSU looks ok, I replaced the main board with another old one and the system is working fine. Except for checking output voltages I have no instruments to deeply test the PSU

I plugged another PSU to the motherboard but it doesn't power up, I removed every peripheral and the CMOS battery and in the next day I'll retry. I double checked and there are no signs of burnt components. Only the usb 3.0 ports if smelled closely the smell of burnt electronics, but there are no signs of smoke

The pcb of the external drive looks visually ok in every component. Upon a close inspection I saw that one of the pins of the mini usb 3.0 connector looks a bit burnt, and it's the only sign of burnt stuff I've been able to find.

I don't know if the pcb still works because I starts a disk only when plugged tu a PC and I don't know if it is now safe to connect it to a PC and to a hard drive.

Thank you very much for your inputs!


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