Fried the diodes on two ST3500320NS, need help sourcing them

[Adrian_]

Hi guys,
To cut a long story short, I idiotically fried the diodes on two Seagate drives by using the wrong cable on a modular PSU. I have a third one purchased at the same time so I've been able to take a photo where the markings on the diodes are visible.

In the picture the diode at the bottom is the one that got fried on both hdd's. if you know what is the equivalent that can be ordered from Farnell or other similar shop please share, any help will be greatly appreciated

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[JGAN]

Where do these trace to? Ground? They might just be regular zener diodes for ESD protection, in which case you can just remove them for the purpose or data recovery.

[JGAN]

If not that logo is ST micro of some sort.

[Adrian_]

Thanks for the speedy answer, i was planning to try and repair the boards if it's only a matter of replacing these parts, as the hdd's were in pretty good shape. I have rather good soldering skills, due to a number of wacky projects, despite my utter ignorance in electronics.

As a matter of fact one of the hdd's still works, even if the diode is burned bad. The other hdd has the diode split in half with the pcb toasted where the connection point used to be.

Here is a wider pic.

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Last edited by Adrian_ on November 15th, 2016, 16:45, edited 1 time in total.

[fzabkar]

A 5V TVS diode can be substituted with an SMAJ5.0A.

A 12V TVS diode can be substituted with an SMBJ12A.

http://www.users.on.net/~fzabkar/HDD/TVS_diode_FAQ.html

[Adrian_]

THANKS a lot fzabkar, this is exactly the info i was looking for. Can you tell me which is which

[fzabkar]

I don't recognise the markings (DUI versus DUJ) but the 5V diode connects to the 5V SATA pins, and the 12V diode to the 12V pins.

http://pinouts.ru/Power/sata-power_pinout.shtml

[JGAN]

Nice resource fzabkar!

If the drive works just probe the voltage across each diode while the drive is on to figure out whether it's the 5v or 12v one.

I would be wary though of using these for crucial data storage, as from what I have read it is possible that the head preamps could be damaged by overvoltage. Although someone more knowledgeable than me might have a different opinion.

[Adrian_]

Thanks again

In case anyone else needs this info, the DUI is 5v and the DUJ is 12v. (checked 0 resistance to the left soldering pad of both diodes from the red and yellow wires of an old school SATA cable using a multimeter) Which makes perfect sense, considering the fact that what happened was basically swapping the wires due to different pinout on two PSU's.

A word of advice to anyone having in house a Coolermaster and a Seasonic PSU's : these have the same connector on the PSU for the SATA cables (5 in line) but the pinout is different.


Now one more question: on one HDD I now have a hole where the soldering pad used to be for the right end of the 5v diode. Can I solder a wire to the right soldering pad of the +12v diode? They are obviously connected on the PCB, is this the correct approach or is there a neater solution?

[Adrian_]

I would be wary though of using these for crucial data storage, as from what I have read it is possible that the head preamps could be damaged by overvoltage. Although someone more knowledgeable than me might have a different opinion.

I thought these diodes were basically designed to fry on a current spike so they protect the subsequent components?

[fzabkar]

Now one more question: on one HDD I now have a hole where the soldering pad used to be for the right end of the 5v diode. Can I solder a wire to the right soldering pad of the +12v diode? They are obviously connected on the PCB, is this the correct approach or is there a neater solution?

Both anodes are grounded, so that should be OK.

[Adrian_]

I was thinking of using a very thin piece of metal (maybe from another diode) to do a neater job.

Anyway, I fired up the HDD with the broken up diode and it works just fine. (even did some testing). I must confess I don't feel at my brightest point right now , probably the list of guys who managed to fry a working HDD on a very good PSU is quite short. Even if those guys at Coolermaster&Seasonic still need a hard kick in their butts for using totally black wires with the same connector but different pinouts on the PSU's.

Will come back with pics after I do the soldering job, hopefully I can find the diodes in a local shop. Was thinking about replacing the 12v as well, they may have heated up pretty bad due to proximity t the 5v ones. Just to stay safe.

[Adrian_]

Hi guys,

The only thing that I've been to purchase locally was the diode in the attached photo. The markings don't match anything I could google, but I've been told by the seller (who didn't sounded particularly sure) that this is indeed a 5v TVS diode.

Hopefully someone knows the logo on the diode and can point me to the right spec sheet. At this point I have some doubts about trying it up, as I may either solder something that doesn't offer protection or even worse, something that could mess things up.

According to this PDF the "BUZ" marking is indeed for the right diode, but only if it's made by ST http://search.alkon.net/cgi-bin/pdf.pl? ... =01973.pdf

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[Adrian_]

Just a quick notice, I added another post with a picture and a link to a pdf datasheet and it's now in moderation (spammer protection I suppose).

[fzabkar]

The logo belongs to STMicroelectronics, so it is a 5V TVS diode.

[Adrian_]

Thanks a lot.

Do you have some sort of logo catalogue for smd's? I did a lot of googling and couldn't find the damn logo on any of the various sites that deal with this domain.

[LarrySabo]

@Adrian, just Google semiconductor logos and you will find many suggestions. Here's an example: https://www.westfloridacomponents.com/m ... logos.html

[Adrian_]

Thanks for the suggestion but the problem is that I've googled trough many of tyese sites without being able to spot that particular ST logo. Hence my previous question.

Fzabkar was able to find it somewhere, so I was curious wether it was online or in some sort of professional catalogue?

[fzabkar]

Fzabkar was able to find it somewhere, so I was curious wether it was online or in some sort of professional catalogue?

I recognised the logo. ST Microelectronics is a major IC manufacturer.

There may be more comprehensive references, but here are the logo sites in my bookmarks:

http://elektrotanya.com/?q=hu/semilogos
http://www.aufzu.de/semi/gif/