All,

A friend brought me an external iomega 2 TB hdd which wouldn't spin, just rapidly flash LED. I opened it and found Samsung HD204UI inside, and moved it to another external HDD enclosure which I know is fine - again same results.

After some reading, I think it might be faulty TVS diode, but I'd like to ask expert opinion before trying to remove it.

When I set my digital multi-meter to "Omega" (Ohm) mode, I get these readings:

1st TVS - 16 Ohm both directions
2nd TVS - 1.4 K Ohm both directions

When I set it to the "Diode" mode:

1st TVS - 0.009 (no units displayed) both directions
2nd TVS - 0.487 one direction, 0.401 the other direction (no units displayed)

Is 1st TVS faulty?

Really appreciate your advice. Here's the picture of the PCB (reusing one from somebody else's post): http://forum.hddguru.com/download/file.php?id=5531&mode=view

Thanks!

Aud

try to remove it and test.

From the readings, both of the TVSs should be bad. But it somehow seem strange .

First, usual disclaimer : if the data is important, take it to someone specialized. By working with componentes in the pcb you can destroy it and also the drive.

I marked the TVS in the picture, just to be sure you tested the correct ones.

First, can you try connecting the hdd directly to a computer ? Inform us of the results.

All the tests should be made with the hdd disconnected from anything. Only power it up when directed to do so.

If you remove both of them , then measure continuity from their terminals to the screw holes. Inform results.

Also, the drive should work without the TVS diodes, so you can remove them (both) and for a test connect the drive directly to a computer ( with a really good power supply, using all the necessary care. Remember the hdd will not be protected agains power surges without the tvs diodes ) . As always, it is your risk, so do not skip steps and power up things before you ask and clear any doubts. Also, if you are not used to working with a soldering iron, better to request the help of a friend or some local AV/TV repair shop.

Rogfanther,

Thanks for the quick reply!

I tried connecting the HDD to the computer, as instructed. I used a 6 year old Dell Zino, which only has space/connection for a single internal drive. Results were so strange that I thought I damaged the computer - pressing power button made the main PC fan constantly tick (a few times per second), as if tried to spin but something was kicking it back. There was no output on the monitor, no beeps, and the power LED stayed off.

However, when I took out the bad HDD and put the good one back in, PC came back to life without any issues.

Before removing TVS and trying HDD without them, I would like to ask what is a "really good power supply". My Dell Zino is always on for 6 years and never destroyed any PCB. Is it good enough? Is there a way to test it?

TVS which I measured are in red rectangle in the attached picture.


Thanks!

Hi,

If with the hard disk your Dell computer didn´t power up, then the TVS diodes ( and maybe other parts ) that have a problem.

By good power supply, I meant something from a good brand, with some adequate wattage. Some other person has a thread in the forum where he has a 300W PSU in a computer where a 500W would be recommended.

I think your Zino is ok .

If you can get both TVS diodes replaced before trying, it would be better. That way, you don´t risk increasing the damage to the disk.

And again, if the data is important, search professional recovery. There are well known and respected members of the forum that should be in cities near you.

I think I'll give one shot - try replacing the TVS and seeing if it starts working. If it doesn't - I'll look into professional recovery services.

Based on multi-meter readings, you believe both diodes are bad right? I should get SMBJ12A and SMAJ5.0A?

Thanks!

From the readings, yes. Even considering some strange intereference like some problem with the multimeter, as these are cheap parts, it doesn´t hurt if you replace both, "just in case".

Just get the right parts, and get it done with care.

Right parts are SMBJ12A and SMAJ5.0A, correct? I can't tell by looking at the PCB, there are no codes on them. I got SMBJ12A and SMAJ5.0A from other posts in this forum.

I ***think*** they are, but the best option would for you to get some kind of magnifier and look at the codes in your disk. Also, take care to replace them in the correct positions.

ISTM that diode #1 (the 12V diode at the LHS?) is bad, in which case the zero-ohm resistor (ooo) would probably measure open circuit. This is typically what happens when a user connects the wrong adapter to the external enclosure. You can flow a blob of solder over the resistor.

_________________
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