Switching pcb between 2 hdd

[Chriss]

Hi!
I found one of my old 80G hdd where the electronic is bad.
I wish to backup the data from, but I cant find anymore the exact hdd to interchange the pcb's to try to
get my data on a safe place.

Here is my ide:
I found to buy in my areal almost the same hdd like mine, just this one is 160G.
The electronic is the same 100% like mine.
Probably I could use the electronic from the donor 160Ghdd on my 80G, but here comes my question:

As the two pcb's are identical, I can probably use the donor electronic on my hdd.
The difference is in the volume size.
the original hdd (bad one) is 80G, the donor is 160G, I have an eeprom on both of them, the same label on the eep 93C76
Do I have to put the original eep on the donor electronic before I can use the donor electronic on the original hdd?
So to say I clone the donor pcb...

What is a "must meet" situation when I searching for a donor pcb?

Would my idea work?
Here are the labels of both hdd.

thanks.

[shakalnokturn]

Hello.

Sorry, no clue if your swap will work, swapping HDD PCB's used to be easy back in the '90s.
As years go by I have less and less success with operations like the one you're considering.
You may get more attention on the eevblog forum in the computing section but I believe the really knowledgeable people on the matter hang out here:
https://forum.hddguru.com/
Or here:
https://forum.acelab.eu.com/

[coromonadalix]

normally  it can / could work if you have the same firmware  BUT  .... youll have to try ??   because  on some boards, the platters and other specs are saved and you need a perfect match  to make it work ?? tried only once on an old 160 gig hdd, it worked to some extent

[mqsaharan]

Search the internet for a similar problem you are facing with your hard drive. If you can find a solution there that might be better than what I am presenting here.
I am in no way an expert but I can tell you the most basic thing that needs to be done.
I went through a similar problem more than a year ago with my laptop hdd. And I learned the hard way that matching the front labels is not very helpful at all.

Make sure that the electronics is bad and not the mechanical parts.
You need to match the numbers and revision on the pcb of both drives. Many different models sometimes use the same pcb.
Assuming that the donor board is OK, you need to replace the bios on the donor board with your original hdd pcb's bios.
And then hope for the best.
Recover your data first before doing anything else.
I am attaching two pictures taken from an ebay auction for more clarification about numbers on pcb and bios.

[fzabkar]

You need to transfer the "ROM" and "NVRAM" chips from patient to donor. The NVRAM contains drive specific information. Some models combine both chips in one.

https://www.hdd-parts.com/13041902.html

There are two smt fuses and TVS diodes near the power connector. I can show you what else to check, if you need help.

The web site is broken, but this article may help you to understand why a straight PCB swap won't work:

http://www.hddoracle.com/viewtopic.php?f=56&t=2600&p=20702#p19090

[Chriss]

Thanks folk for this valuable infos.
The data on my old hdd is nothing important, I'm just wanna give a try, learn something totally new for me. :-)

When I saw the 93Cxx eep I was almost 101% sure does there must be some calibration data and ither important data.
So probably I need to program or change the eep on the donor pcb.

For now, I will give a try to identify the problem on my hdd and try to repair if possible.

The problem is, when I connect the hdd to any pc, the pc wont power on.
I assume something is in short on the pcb.

I have to check.

Is there out any place maybe where I vould find se schematics for hdd electronic?

I'm totally new to this type of electronics and have no practice but I have almost everything in my lab to even change the cpu too if needed. :-)

[fzabkar]

Check the TVS diodes (D4 and D3).

https://sep.yimg.com/ay/yhst-14437584971410/hds721010kla330-0a29689-0a29470-0a29636-0a33863-ba2469-oa29689-oa29636-oa29470-3-5-sata-hitachi-circuit-board-fw-4.gif

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

Q1, Q2 and Q3 would be the pass transistors for the linear regulators. The emitter terminal (BCE) would be Vout.

L3 and L1 are part of a Cuk converter which generates the -5V supply for the preamp on the headstack.

Tutorial - Linear and Switchmode Regulators used in HDDs:
http://www.hddoracle.com/viewtopic.php?f=59&t=231

[Chriss]

I found 1 diode in short.
The label on the diode is:
ST VU
BBE
GP747 ( on the pic I made a typo error, it is GO on the pic, but should be GP )
Does somebody know what type of diode is this?
I asse this is a TVS diode.
The 12V rail is in short to gnd through this diode.

If I just remove the diode and try to power on the hdd for moving the data to another hdd, is this a smart option or a suicide option? :-)

Thanks.

[fzabkar]

That is a 12V TVS diode. If there are no other problems, and if your PSU is good, then the drive can be operated without this diode.

SMBJ12A, STMicroelectronics, TVS diode, 600W, 12V, marking BBE:
https://www.st.com/resource/en/datasheet/smbj.pdf

If you intend to replace the PCB, then you may face one complication. In addition to a mandatory transfer of the NVRAM IC (U5), you will need to ensure that the donor PCB has compatible firmware. That's because the "ROM" code is embedded within the MCU (U1) rather than U7 (which is unpopulated).

My approach would be to remove the shorted diode and then power up the PCB on its own. Measure the voltages at the emitters of Q1, Q2 and Q3. I expect you will find +3.3V, +2.5V and +1.2V.

Then measure the voltages at the capacitors in between the two coils. You should find -5V somewhere, unless the MCU has switched off this supply rail.

Edit:

If you have the appropriate tools, it would be prudent to dump the NVRAM contents to a backup file.

[Chriss]

Thanks for this nice explanation, I can r/w the NVRAM, I will give a try...

[Chriss]

So, the task is managed.
The shortening was related to the tvs diode.
I removed it from the pcb and the hdd was working again.
I fid a backup of the hdd and now is everything ok.

Thanks to everyone for the help.
I really appreciate your help and time.