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 Post subject: Hitachi 4TB HUS726040ALE614 No Power
PostPosted: June 19th, 2019, 14:58 
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Joined: March 24th, 2010, 21:08
Posts: 111
Location: California
Got a Hitachi 4TB HUS726040ALE614 from a G-Drive enclosure. PCB PN: 0J50178. No signs of life when power is connected. PCB has no signs of damaged or burned components and nothing heats up when power is applied to bare PCB. Thinking PCB + ROM swap. Suggestions? Thanks.


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 Post subject: Re: Hitachi 4TB HUS726040ALE614 No Power
PostPosted: June 19th, 2019, 15:52 
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I don't have firmware tools unfortunately. Here's a pic
Image


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 Post subject: Re: Hitachi 4TB HUS726040ALE614 No Power
PostPosted: June 19th, 2019, 18:03 
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Joined: September 8th, 2009, 18:21
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Location: Australia
Check that PUIS is not enabled. You can disable PUIS with HDAT2.

Check the TVS diodes and fuses.


Attachments:
TVS_fuse.jpg
TVS_fuse.jpg [ 77.6 KiB | Viewed 10091 times ]

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 Post subject: Re: Hitachi 4TB HUS726040ALE614 No Power
PostPosted: June 20th, 2019, 6:54 
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What is the function of the 2-strip component between the fuse and the tvs of the 5-volt line?

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 Post subject: Re: Hitachi 4TB HUS726040ALE614 No Power
PostPosted: June 20th, 2019, 7:12 
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https://docviewer.yandex.ru/view/454118 ... J9&lang=en


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 Post subject: Re: Hitachi 4TB HUS726040ALE614 No Power
PostPosted: June 20th, 2019, 14:39 
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fzabkar to the rescue once again. thank you for the tip! I should have caught that myself... next time.

12v fuse and 12v tvs diode were both toast. replaced them & bam, drive up and running. extracting the data now.

Thanks to everyone else for the other suggestions as well!


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 Post subject: Re: Hitachi 4TB HUS726040ALE614 No Power
PostPosted: June 20th, 2019, 18:06 
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mhp666 wrote:
What is the function of the 2-strip component between the fuse and the tvs of the 5-volt line?

That appears to be a Schottky rectifier diode. Often it exists on its own, without the parallel connected TVS diode, in which case it provides protection from reverse polarity. However, I confess that I don't understand why it is needed in this case since the TVS diode should provide the same protection and more. :?

BTW, automotive equipment often has "d*ckhead diodes" to contain the damage in case the user reverses the polarity of the battery.

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 Post subject: Re: Hitachi 4TB HUS726040ALE614 No Power
PostPosted: June 21st, 2019, 6:59 
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managerharry wrote:
That appears to be a Schottky rectifier diode. Often it exists on its own, without the parallel connected TVS diode, in which case it provides protection from reverse polarity. However, I confess that I don't understand why it is needed in this case since the TVS diode should provide the same protection and more. :?

BTW, automotive equipment often has "d*ckhead diodes" to contain the damage in case the user reverses the polarity of the battery.


hanks for the info.
I would have seen logic in a capacitor, as a low frequency filter.

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