Replacing PCB on Hitachi HDT725025VLA380

[stefax2001]

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.

[fzabkar]

https://www.hdd-parts.com/17110243.html

[stefax2001]

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.

[fzabkar]

What's wrong with the original PCB?

[stefax2001]

What's wrong with the original PCB?

Attachments

[fzabkar]

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

[stefax2001]

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

D4:0Ω
R5:0Ω

[fzabkar]

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.

[stefax2001]

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?

[fzabkar]

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.

[stefax2001]

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:

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

Was this:

Top plastic part of D4 is melted.

[fzabkar]

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.

[stefax2001]

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.

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.

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

[fzabkar]

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

[stefax2001]

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 (60.29 KiB) Viewed 32058 times

[fzabkar]

You can try a donor PCB, but be prepared for a bad preamp, in which case you may be wasting your money.

[stefax2001]

So donor PCB should be compatible?

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

[fzabkar]

They have different MCUs (0A29625 vs 0A29626). I'm not a DR pro, but I would think that the PCBs would be incompatible.

[stefax2001]

Ok,thank you.