Need a little help with a ST32000542AS with burnt TVS...

[MadOCer]

Hi guys,

I have a ST32000542AS here with a burnt TVS. In the following pic you see a quite big burn mark. BUT, that's not where the TVS used to be. The TVS is the bigger chip right next to the burn mark.

http://www.hs-augsburg.de/~ingmar_k/ST32000542AS.jpg

Now my guess would be that the two parts that went up in smoke right there were some smd capacitors. I would just like to have some confirmation from someone with a ST32000542AS or just any other drive with the same or very similar PCB.

Thank you very much in advance for any help! It's highly appreciated.

Greets

Ingmar

P.S.: The TVS is shorted to GND, so it's very likely that with a new TVS and the replaced parts, this disk should be as good as new, if I'm lucky.

[jono-ats]

You won't be lucky. There are traces that are burned open. Better to start with a fresh PCB.

[networkpc3000]

try to replacement TVS and solder cable connect with which circuit are burned open. good luck.

[MadOCer]

Ah,thanks, I didn't realize that the one furthest down was a complete trace and not just two solder pints, like the two above it.
And nevermind, soldering won't be the problem. I just wanted to be sure what it was that went up in smoke. So if you have such a PCB, please post a pic. In the meantime I'll remove the TVS and see what I can find out with a little measuring.

[MadOCer]

OK, thinking about it, there were no visible leftovers of any parts, so it seems that just this one trace burnt/melted and the 4 solder-pads above it were empty to begin with. Probably just pads for some extra small filtering smd caps that were left out due to cost. Anyway, that would make sense. The pads above the trace probably just were affected by the heat of the burning trace.

[jono-ats]

Well, you don't know at this point if there are other downstream components that have gone bad, etc. It's YOUR time. Have fun.

[MadOCer]

I know. I only do this for fun. I neither need the drive, nor do I need the data on it.

BTW, I just removed the TVS and cleaned up the burn marks.

http://www.hs-augsburg.de/~ingmar_k/ST32000542AS-2.jpg

As can be seen, the 12V planes (the three traces on the bottom) are all disconnected from the circuit. That's why the drive didn't do anything when connected. And one can also see that what burnt up was not a trace, but actually it was some part (the solder pads can still be seen) that connected the 12V planes to the circuit.

The question is: what was used by Segate?

Two possibilities: Either zero Ohm resistors, or inductors to further filter the 12V line. My first guess would be that it were inductors, because those are current limited and probably burnt up because of that fact, when the short circuit, caused by the TVS happened. Unfortunatel the same thing applies to resistors.

Anyone with further details?

[MadOCer]

Reconnected the 12V plane and the Seatools scan is running right now. Let's see what the outcome will be.

[MadOCer]

OK, the disk seems to be absolutely OK. Let it run with Seatools over night. No problems at all. As soon as the new TVS is here the disk will be put in a external e-Sata box and will be used for uncritical storage on my 3 systems. Nice to have it up and running again.

[DrFaustus]

good job, welcome to the world of patience & perseverance

[cangavi]

Hi,
exactly the same happened to me as well, same hdd, the TVS burnt out but seems that the rest of components in the surrounding area are OK.
MadOCer, can you let me know the specs, P/N of the TVS and where to find one, Farnell maybe?
Thanks in advance

[fzabkar]

Hi,
exactly the same happened to me as well, same hdd, the TVS burnt out but seems that the rest of components in the surrounding area are OK.
MadOCer, can you let me know the specs, P/N of the TVS and where to find one, Farnell maybe?
Thanks in advance

The 12V TVS diode can be substituted with an SMBJ12A, and the 5V TVS diode with an SMAJ5.0A. Farnell should have both.

[cangavi]

Thank you fzabkar, best regards.