Hello all,

First post here - hi everyone.

Would really appreciate any help / advice.

I have stupidly managed to use the wrong power source with my external hard drive, and it would appear I have overvolted the unit.

Having done a bit of research, I'm hoping I can remove the TVS diodes to allow the unit to function, even temporarily, to allow me to retrieve some important files.

Can anyone tell me where the TVS diodes are, and give me some diagnostic procedures to check if there is any hope that this is a solution?

Thank you so much for your help!!

PCB

Here I have a perfect idea for you on this one. We have a wave of these in here right now and there is one guy Franc who loves these issues. You can search on him fzabkar and look for his posts. He will talk to you about mulit meters, solidering , rails and all kinds of stuff. Sorry now people are just not answering these types of posts. I am sure after this he will be here right away with all his cut and paste solutions to you on this one. So do a search on his name and you will find it quite easily here on the forum. I know it is not your fault on this one but we have seen too many of these lately and it seems that is all that is here now.

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Iorana Haraharaini

Lack of fantasy... it's because it's December...

http://farm6.static.flickr.com/5202/525 ... 740c_b.jpg

Referring to the above image, can you tell me the marking codes on D5 near the power connector, and the two diodes at the top of the photo, to the right of the motor connector?

Note that your board has an 8-pin external flash memory at U12. If you replace your board, then this chip, or its contents, will need to be transferred to your donor PCB.

If you have a digital multimeter, set it on the 200 ohms range and measure the resistances of D5, the two diodes at the top, the 0 ohm resistor in the top RH corner, and R81, L4, and L1 near the power connector.

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A backup a day keeps DR away.

The markings are:-

D5: AE / GP614 (may be 6P614)
Top diode LH: G30 / GP625 (may be 6P625)
Top diode RH: 8UF (or BUF) / GP625 (may be 6P625)

Resistances:

D5: 1
Top diode LH: 1
Top diode RH: 00.7 (reading seemed to fluctuate)
0 OHM resistor top right 28.2
R81: 00.5
L4: 00.5
L1: 1

What's the prognosis???

Thanks for your help

D5 is a 5V TVS diode, p/n SMAJ5.0A. "AE" is its marking code, and "GP614" is a YWW (Year / Week) data code, ie week 14 of 2006.

http://www.st.com/stonline/products/lit ... 4/smaj.pdf

"BUF" is the marking code for a 13V TVS diode, p/n SMBJ13A.

http://www.datasheetarchive.com/pdf-dat ... 631289.pdf
http://www.st.com/stonline/products/lit ... s/5616.pdf

When you list the resistance as "1", do you mean that the meter overranges, ie is the reading the same as when you hold the probes apart in the air? If so, then the 12V TVS diode is shorted, and the 0 ohm resistor in the top right corner is open. You can remove the diode by snipping its pins with flush cutters, and bridge the resistor with a blob of solder, or a wire link. Assuming there are no other problems, your drive will work without the diode, but it will no longer have any overvoltage protection on the +12V supply.

If you wish to replace the diode, you should be able to obtain one from Farnell.

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A backup a day keeps DR away.

Sorry, have to clarify:-

So the top RH diode is the 12V TVS that should be removed?

And by bridging the 0 Ohm resistor, I don't have to remove it, just bridge it with the component still in place, connecting the terminals as you mentioned?

I think the meter must be over-ranging as suggested, not entirely sure though! (sorry!)

Thanks again.

Yes and yes.

Good luck.

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A backup a day keeps DR away.

Thank you very much for your input.

Will keep you posted.

Hi Fzabkar,

Just to let you know, have removed the TVS diode and I'm delighted to say IT WORKED!! Thank you so so much!!!