Hello Frank,Sean ,Jared ,Luke Sir and everyone else ,

I too have had my own experiences with the Samsung Drives But not on the 025 but the 024's .I have initialized knocking drives with PC 3000 And then managed to clone even the head that was making the drive click .As Far As Head Replacements And Head Unstuck Issues Are Concerned These Drive Have One of The Most Solid Heads i Have Seen In Any Drive in My Experience Atleast .The Best Method To Unstick Them Is To Use a Head Unstuck Tool Like ertools ,But even Force Dragging To Ramp In More Then 75% Is success .Sometimes Even The Easiest Case Of Head Unstuck Will Have a Head Failure Mostly Top Head No 4 .If You Have a Powerful Magnifier You Can Inspect Heads Inside HDA Assembly Also ,Recently i Had a Case Where The Heads Would Not Go Back On Ramp And i Had To Remove Ramp ,Heads Inspect Them And Install everything And i Got Just 14 Bad Sectors In Cloning

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Regards
Amarbir S Dhillon , Chandigarh Data Recovery Labs [India]
Logical,Semi Physical And Physical Data Recovery
Website-> http://www.chandigarhdatarecovery.com

Thank you. I bought a brand new USB 2 TTL cable and tried, but was not successful. Maybe I'm wrong on something. I connected the green cable to the pin closest to the sata interface, which should be TX. The white one next, should be RX.
Then attached the USB cable to the PC. It shows up as /dev/ttyUSB0.
Used putty with 38400 baud, 1 stop bit, no flow control. The connection window spawns as i issua the open click but nothing gets shown.
Tried HE, LB but no response.
What do I miss?
Thanks for your patience!

I tried and connect the cable to the [donor SATA PCB + not spinning hdd]. At first i could not get the connection, but after a few hours (......) i realized that the TX/RX had to be inverted.
When the disk was connected to the PC (via a SATA2USB device) the communication took place at 57600 baud. At 38400 text was scrambled and unreadable.
Anyway, the pcb kept saying LED 2A01, which I learn is a mismatching PCB error.
So I swapped again to the [maybe damaged USB PCB + not spinning HDD], but now i'm stuck, because i cannot connect.
The voltage at the terminal points doesn't go higher than 0.78 V, and it sounds a bit strange to me because the SATA PCB terminals were at about 2.7V.
Any help?
Thank you very much. keep trying...
Marco

Actually, i realized that the voltage must be measured between TX/RX and GND. RX vs GND is 3.3V while TX vs GND is zero... sounds strange: i guessed they were to be equal.
Still many many things to learn...

I'm totally puzzled. The voltage between RX and the hdd chassis is 3.4V. Between TX and the chassis is 0.0V. Between RX and TX is 1.2V!!!!!!

It was the USB cable that provided the voltage. Once removed, the PCB is completely dead. I tried an USB 2 cable too without any changes. Now I'm pretty sure the PCB is dead and I need to find a donor, since the sata pcb I got from the bad sectored HDD seems not to be compatible though I managed to connect to it. I hope the drive itself has no spindle motor issue...

@centosette, I'd like to help you, but I need photos ...

http://ep.yimg.com/ay/yhst-144375849714 ... 6013-7.gif
http://ep.yimg.com/ay/yhst-144375849714 ... 6012-8.gif

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A backup a day keeps DR away.

Rear and front view. Here they are. Thanks a lot.

I've marked my best guesses as to the voltage test points.

_________________
A backup a day keeps DR away.

ISTR another thread where a user determined that there was a fault in the component that filters the output of the 3.3V bridge supply (see first attachment). I suspect that it may be a low pass T-type LC filter. The Murata device looks like it might fit the bill, although it is specified for signal lines rather than power lines. The same component appears to be used in the "unknown function".


NFL18ZT, Murata, T-type LC filter, EMI suppression for signal lines:
http://www.murata.com/en-us/api/pdfdown ... 107H1A3%23
http://www.mouser.com/ds/2/281/c51e-794816.pdf
http://www.murata.com/~/media/webrenewa ... ashx?la=en

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A backup a day keeps DR away.

I tested all of the checkpoints, but voltage is zero for each. I grounded both the PCB and the voltmeter to a common metal body (old damaged eide HDD).
Something is wrong with power supply, it seems. Is there a way to supply power bypassing the USB interface? I could try and provide 5v at some point on the PCB. I should find the right contacts on the available side, naturally, not the one facing the HDD. Or would it make sense to try and do that without screwing the PCB onto the HDD and connecting via the terminal?
Thank you!! Very kind of you helping me.

I found this thread and tried the checkpoint "Point A". It seems to be the same problem as it was for the guy.

https://forum.hddguru.com/viewtopic.php ... ile=mobile

Pushing slightly the solder of the black component causes the led to light up!! So maybe I only need to "reflow the solder". And here comes the problem: what does it mean? I think it means to heat up (not too much) the solder, cause it to become soft and stick again so that the contact gets back to functioning... am I right? you can laugh...

Yes, that's right. You can wet it with a little bit of fresh solder, if necessary.

Best of luck.

BTW, I don't understand how you were able to measure 3.3V at Tx/Rx if this component was open circuit.

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A backup a day keeps DR away.

I have added the test points for the TVS diode and associated components.


For the benefit of others, that "unknown" component could be a 3-terminal capacitor rather than an LC filter:

NFM18PC, Murata, EMIFIL 3-terminal SeriesFeed Through Capacitor for power lines:
http://search.murata.co.jp/Ceramy/image ... FM18PC.pdf


Here is a thread where a user replaced a similar part with an smd fuse:

https://forum.hddguru.com/viewtopic.php?f=1&t=29654
https://forum.hddguru.com/download/file ... &mode=view

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A backup a day keeps DR away.

I was surprised as well, then I guessed it could be the terminal cable itself that was providing the voltage. After disconnecting the USB 2TTL cable, everything was dead at the terminal endpoints. I didn't know that the cable could provide energy from the TX terminal (green cable)...

OK, so the cable was attached to the PCB when you took your measurements. That makes sense now. Sorry for the misunderstanding.

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A backup a day keeps DR away.

Ok, the trick worked great! I've resoldered the 0-ohm resistor (someone will explain what it is for... sounds like a zero-cash bank account) by keeping the soldering iron tip on one endpoint at a time for about 25 secs. I tried the first time keeping it less time because i was afraid to mess it all up and burn something, but it didn't worked. So i embraced my courage and that's it... it worked fine, being my first almost-soldering!
I really want to thank all of you and particularly fzabkar that has been such a helpful and generous guy! Hope one day i can repay you.
It's been my first hdd recovery and I had a lot of fun, after all!
Good night (for this side of the globe)!
Marco

The resistor is often fusible, otherwise the same position can be occupied by an smt fuse. It just depends on how cheap the manufacturer is feeling at the time.

When there is an overvoltage, or reversed polarity, on the +5V USB supply, the 5V TVS diode goes short circuit. This then causes the "fuse" to go open circuit. That said, such a fault is very unlikely for USB powered drives.

BTW, Samsung's HDD PCBs seem to have a lot of problems with dry solder joints, even in their 3.5" drives. I wonder if this may be due to the use of lead-free solder mandated by RoHS. Lead-free solder requires higher soldering temperatures than leaded solder.

Congratulations anyway.

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A backup a day keeps DR away.