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 Post subject: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: May 30th, 2020, 14:41 
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Location: Serbia
Hello,can you help me?

I have 2 HDDs:

First one is:

Hitachi
Model:HDT725025VLA380
P/N:0A33423
MLC:BA2367
Main controller IC:0A29626
PCB Label:
    0A53043
    BA2178_
    Xda733
    OCTH
Board number:F 0A29531 01

And second is:

Hitachi
Model:HDS721616PLA380
P/N:0A33932
MLC:BA2357
Main controller IC:0A29625
PCB Label:
    0A53039
    BA2178_
    Mda748
    9678
Board number:F 0A29531 01

First hdd pcb is fried and second hdd is full of bad sectors.
Is it possible to replace pcb on first hdd with pcb from second hdd (I know i will have to replace 8-pin chip)?



P.S. Sorry for my bad english.


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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: May 30th, 2020, 15:07 
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https://www.hdd-parts.com/17110243.html

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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: May 30th, 2020, 15:18 
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Quote:
1. As long as your board Sticker is 0A53047 and Main Controller Chip is 0A29626 and Board Number is 0A29531 ,our board is same as yours in hardware


Well i guess i can't use second hdd as donor :( .

tnx for help.


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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: May 30th, 2020, 15:26 
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What's wrong with the original PCB?

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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: May 30th, 2020, 15:32 
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fzabkar wrote:
What's wrong with the original PCB?


Attachments:
IMG_20200530_212755.jpg
IMG_20200530_212755.jpg [ 2 MiB | Viewed 8986 times ]
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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: May 30th, 2020, 15:53 
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That's the 5V TVS diode. It appears that your drive sustained an overvoltage on the 5V input. Hitachi drives aren't very well protected, so there is a risk that the preamp is damaged.

Do you have a multimeter? Can you measure the resistance of the diode, D4, and the adjacent resistor, R5?

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

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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: May 30th, 2020, 16:31 
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fzabkar wrote:
That's the 5V TVS diode. It appears that your drive sustained an overvoltage on the 5V input. Hitachi drives aren't very well protected, so there is a risk that the preamp is damaged.

Do you have a multimeter? Can you measure the resistance of the diode, D4, and the adjacent resistor, R5?

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


D4:
R5:


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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: May 31st, 2020, 14:33 
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Am I right in assuming that the drive now causes your PSU to shut down? If so, then remove D4 and your PCB will probably work again, albeit without protection on the 5V input.

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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: May 31st, 2020, 19:16 
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fzabkar wrote:
Am I right in assuming that the drive now causes your PSU to shut down? If so, then remove D4 and your PCB will probably work again, albeit without protection on the 5V input.


Yes PSU shuts down when i connect contacts of broken diode.

I checked resistance of diode D4 and resistor R5 again (with different multimer) and got -1018Ω for D4 and -1658Ω for R5???
A bit dumb question,but did i make some mistake or what?

Should i still remove D4?


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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: May 31st, 2020, 20:42 
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stefax2001 wrote:
Yes PSU shuts down when i connect contacts of broken diode.

What do you mean by this?

I wanted to know whether the PSU shut down when the broken HDD was originally connected to it. You didn't say how the drive came to be damaged.

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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: June 1st, 2020, 4:31 
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fzabkar wrote:
What do you mean by this?

I wanted to know whether the PSU shut down when the broken HDD was originally connected to it. You didn't say how the drive came to be damaged.

What i meant when i said:

stefax2001 wrote:
Yes PSU shuts down when i connect contacts of broken diode.

Was this:

Attachment:
File comment: Top plastic part of D4 is melted.
IMG_20200601_095236.jpg
IMG_20200601_095236.jpg [ 1.84 MiB | Viewed 8767 times ]

Attachment:
IMG_20200601_095243.jpg
IMG_20200601_095243.jpg [ 2.82 MiB | Viewed 8767 times ]

Attachment:
IMG_20200601_095231.jpg
IMG_20200601_095231.jpg [ 2.95 MiB | Viewed 8767 times ]


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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: June 1st, 2020, 19:53 
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Your statement implies that you connected a PSU to the diode rather than to the HDD, in which case it makes no sense. Or do you mean that you "reassembled" the broken diode and then reconnected the HDD to the PSU???

Whatever you did, your latest measurements indicate that the diode has gone open circuit, and resistor R5 is now also open. IIUC, this resistor is in series with the 5V supply to the preamp, so there is a real possibility that your preamp is shorted. You can test for this possibility by measuring the resistance between ground and R5, and then comparing the result with the PCB on and off the drive.

It goes without saying that you should check the 5V and 12V outputs of your PSU. Obviously there was an overvoltage on the 5V output, so either the PSU is faulty, or you have used the wrong modular cable.

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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: June 2nd, 2020, 10:43 
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fzabkar wrote:
Your statement implies that you connected a PSU to the diode rather than to the HDD, in which case it makes no sense. Or do you mean that you "reassembled" the broken diode and then reconnected the HDD to the PSU???

I normally connected PSU to HDD with molex and then "reassembled" diode.

fzabkar wrote:
Whatever you did, your latest measurements indicate that the diode has gone open circuit, and resistor R5 is now also open. IIUC, this resistor is in series with the 5V supply to the preamp, so there is a real possibility that your preamp is shorted. You can test for this possibility by measuring the resistance between ground and R5, and then comparing the result with the PCB on and off the drive.


When you said "PCB on and off the drive" you mean literally disassembling PCB from HDD?
Anyway i got -1003Ω for both measurements on and off.

fzabkar wrote:
It goes without saying that you should check the 5V and 12V outputs of your PSU. Obviously there was an overvoltage on the 5V output, so either the PSU is faulty, or you have used the wrong modular cable.

I already checked PSU and got: 5.27v and 11.70v


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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: June 2nd, 2020, 15:33 
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The resistor should have a value of 0.47 ohms.

I would measure the resistance to ground at the preamp end, if you haven't done so already.


Attachments:
R5.jpg
R5.jpg [ 199.22 KiB | Viewed 8649 times ]

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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: June 2nd, 2020, 18:59 
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fzabkar wrote:
The resistor should have a value of 0.47 ohms.

I would measure the resistance to ground at the preamp end, if you haven't done so already.


I got this.


Attachments:
R5.jpg
R5.jpg [ 60.29 KiB | Viewed 8623 times ]
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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: June 2nd, 2020, 19:44 
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You can try a donor PCB, but be prepared for a bad preamp, in which case you may be wasting your money.

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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: June 2nd, 2020, 20:53 
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Joined: May 30th, 2020, 14:18
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So donor PCB should be compatible?

stefax2001 wrote:
This HDD (with bad PCB):

Hitachi
Model:HDT725025VLA380
P/N:0A33423
MLC:BA2367
Main controller IC:0A29626
PCB Label:
    0A53043
    BA2178_
    Xda733
    OCTH
Board number:F 0A29531 01

Donor HDD:

Hitachi
Model:HDS721616PLA380
P/N:0A33932
MLC:BA2357
Main controller IC:0A29625
PCB Label:
    0A53039
    BA2178_
    Mda748
    9678
Board number:F 0A29531 01


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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: June 2nd, 2020, 21:08 
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They have different MCUs (0A29625 vs 0A29626). I'm not a DR pro, but I would think that the PCBs would be incompatible.

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 Post subject: Re: Replacing PCB on Hitachi HDT725025VLA380
PostPosted: June 3rd, 2020, 8:23 
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Joined: May 30th, 2020, 14:18
Posts: 10
Location: Serbia
Ok,thank you.


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