Replacing PCB diode question - Samsung HD154UI

[peezey01]

Hi guys, my housemate accidentally plugged the wrong power supply (higher voltage) into my HDD enclosure which contained my Samsung HD154UI. There was a bit of smoke and now the HDD is dead.

From what I can tell (but I'm not entirely sure) it looks like one of the diodes on the PCB got burnt as it is has turned a bit brown and is slightly off-centre - shown in the picture below.

I did some reading about swapping the PCB but found that the chances of finding a perfect match for these new Samsung models is pretty slim, so that option probably won't work.
PCB label says:
TRINITY 32MB REV5
BF41-00206B R00

Then I read that the diodes near the SATA power connector might just be for overvoltage protection and that my drive may still work if I simply remove them with flush cutters... though it will no longer have any overvoltage protection. Any thoughts/ideas on this? And how difficult would it be to replace the burnt diode/s?





Thanks for your help,
Pete

[momo2010]

Hello peezey01
I have the same problem,
Before attempting to cut the diodes you better try to test them with a simple Multimeter tester (Very cheap, you can find it anywhere).
Set the diode mode test (Generally in the last resistance mode: 200 Ohm ->|-) If its okay it should conduct the current in one direction only (in the first you have 1, in the second sens you will have some value).
If its burnt its conduct current in the two direction and have 0 Ohm resistance.
For me i'm actually about swaping the EEPROM circuit.
Good luck

[peezey01]

Thanks a lot. I'll check them with a multimeter.

So if they conduct current in two directions and have 0 resistance it is safe to cut one or both of them off?

Do you think I'll have any problem plugging the hard drive in after that and backing up all of its contents to another HDD?

And regarding replacing the burnt diodes, where could I find matching diodes and how will I know what diodes I need to buy? Also, where can I find them and I how would I go about attaching them? Just a soldering iron?

Thanks,
Pete

[fzabkar]

The circled component is the 12V TVS diode. You can replace it with an SMBJ12A from Farnell, Mouser, Digikey. The diode to the right of it is the 5V TVS diode. It can be substituted with an SMAJ5.0A. To the right of the 5V diode is a zero-ohm link which sometimes goes open like a fuse.

[peezey01]

One of the diodes has 6.7 ohm resistance in both directions and the other has 0 ohm in both directions.
Which one/s should I cut off?

Pete

[fzabkar]

Neither number looks right. Are you measuring the resistances on the 200 ohms range, or 200K?

[peezey01]

At first I measured it with an auto-range multimeter and got the above results.

Then I went and bought one that measures on the 200 ohms range and I'm getting a similar result.
It reads 7.4 in both directions for one diode and the other diode gives no reading in either direction (ie. stays on 1).

What should I do?

Thanks,
Pete

[fzabkar]

When you say "no reading", do you mean that the "1" is indicating overrange, just it does when you hold the probe tips apart in the air? If so, then that particular diode is OK.

The one that reads 7.4 ohms in both directions is probably OK, too, although the low resistance is a worry. TVS diodes usually go short circuit (zero ohms) when they fail, so your resistance measurement may be indicating a fault elsewhere on the board. Carefully desolder and lift one of the diode's pins. Then measure the resistance of the diode on its own, and the resistance between the pads on the PCB. This will tell you whether the diode is responsible for the low resistance, or some other component on the same supply rail.

BTW, which diode is measuring 7.4 ohms?

[peezey01]

Ok I'll give that a go, thanks.

The diode that I circled in the image above is measuring 7.4ohms and the one next to it reads 1 exactly as the multimeter does when the probes are apart in air, yes.

[peezey01]

On second thought I'm thinking that might be too much effort and I may end up burning the board if I tried it.

Am I basically stuffed if the diodes are fine and it is something else on the board causing the problem?
If so, I might just cut the diodes off one by one and try connecting the drive. Which one should I start with? The 7.4ohms one which is slightly browned?

Thanks,
Pete

[fzabkar]

The 5V diode is OK. Did you test the "000" link to the right of it? It should measure zero ohms.

The 12V diode is the usual suspect in your case. However, it normally measures zero ohms after a failure. Measure it again, but this time remove the board from the drive. This will eliminate any low resistance paths through the motor or voice coil.

BTW, when you touch the probe tips together, what resistance do you measure?

[peezey01]

I ended up just ripping off the 12V diode before I read your post and the drive works fine now

Thanks!

[mz6xy6]

You replaced the 12V diode or just took it out???

I just had my son plug 19Vdc into the 12Vdc USB case connector. My Samsung drive PCB is layed out similar (at least the diodes) to yours. The 12Vdc may be slightly tinted brown on one end. I get the electrical smell when I plug it in. Can't see where the smoke is coming from or see any blown chips.
The diode on the left (12v) is thinner than the one on right (5v).

Mines a Samsung HD103SJ Rev A. 1TB 2009.10 (in a Verbatim USB case)

Also, did your USB PCB board in your USB case still work or was it fried too?

Thanks

[ROb]

Just remove the burnt diode and you are done copy the data Enjoy !!!!!

[jokersmile]

Hi ,

Firstly Sorry for my english.

I have the same HDD (HD154UI) too. And i have read this topic and remove 12V diode. And it works.

I try to change 12V diode but i dont find SMBJ12A.

But today it doesnt work anymore and no sound on HDD. What's the problem right now ?

[fzabkar]

@jokersmile, did you fix the original problem? That is, did you find out why the drive was overvolted? If not, then you may have overvolted your drive again, although this time it would have been unprotected.

[jokersmile]

@jokersmile, did you fix the original problem? That is, did you find out why the drive was overvolted? If not, then you may have overvolted your drive again, although this time it would have been unprotected.

@fzabkar i didnt fix the problem, cause i didnt find the diode in my country.

It has been worked without diode for few days. But now HDD looks like dead.

[fzabkar]

@fzabkar i didnt fix the problem, cause i didnt find the diode in my country.

It has been worked without diode for few days. But now HDD looks like dead.

As Spildit has said, the problem I was referring to is in relation to the external PSU.

If you wish to troubleshoot your board, measure the voltages at each of the two 4R7 coils, or upload a photo of your PCB. You can test the PCB off the drive. Use a different PSU, though.

[jokersmile]

My PCB photo is here.

Attachments

[fzabkar]

Can you measure the voltages at the indicated points? You can use any screw as your ground reference.

There appears to be a missing capacitor, but the photo isn't clear. Can you confirm if this is the case, and if so, did you remove it?

Attachments

5V_TVS.jpg (70.5 KiB) Viewed 20981 times