Question about Hard Drives

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Burnt Components Hello azkeyz, I agree with you because I applied 12v when I should've applied 5V. Any idea if there is a diode etc.. on 5 v line that I may have burnt out. Thanks

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  • aftershock Sep 11, 2008

    Thanks for confirming, but I guess I should put my 100W soldering gun away!


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I just fixed one that my son plugged in with the 5 and 12v rails swapped over.

It was a seagate 160gb barracuda. The 5V line measured dead short to ground, so I did the smoke test with a 5V at 2A psu and the part that smoked was a 6V2 zener which is connected across the 5V rail as a crude over voltage protection

Posted on Dec 31, 2008

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Well from my days in electronic technician school , embarased to say their name because they are not recognised officialy , but my teacher was one hell of a guy Art Scott

we would use a diode on any 5v or 12v power supply line , if it's DC to prevent voltage back flow

which in your situation you got a DC circuit , from what I understand

and that would mean it would be a VERY good idea to USE a diode to prevent any unwanted back flow of voltage , specialy in a DC power feeding line , you don't have to but it's a good idea.
in some situations you absolutely have to if it's a DC critter as in a bridge rectifier or

hey just a side thought , there are 4 diodes in a bridge rectifier for turning AC into DC ,

I would need a detailed circuit print out to be able to tell you whats really going on.

doubtful that you have a bridge rectifier situation happening , probably you just have a blown diode
on the 5v power feed line. that would be extremely good news , as thats easy to test and replace
unless it's a surfface mounted diode micro type.

the history of the diode can get long winded in a hurry , the shotkey family made the shotkey diode
it's more for AC circuits to kinda sorta replace a coil or bridge rectifier , it's excellent as a voltage smoother...

but you're probably dealing with just an ordinary zener diode PNP , or NPN , who really knows without the schematic or testing it , you know the story

it's extremely difficult to deal with microcircuits these days , without a lab and the extremely expensive tools to work on them , such as electron microscope lol , the electronics industry
which is basicaly IBM and the others lol don't really want the general public to be able to work
on anything , shhh it's conspiratorial thinking lol

you just kinda opened up an old wound is all , back then I thought the specifications of a diod would never change and that I would be able to build anything electronic that I wanted , but now thats changed and you need machines to make machines now , it hurts my geek pride a bit but I'll get even one day lol

I don't really know what to say except try your best with what you have , and if you simply feel this
situation is beyond your ability , it's not shameful to send it to people who can fix it.

I admire you for trying , and I appreciate you , you made this old ( in geek terms ) 38 year old engineer feel better about things , and made me reflect.

Posted on Sep 11, 2008

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Hi Jorge
Internally a standard 3.5" Hard Drive uses two voltages
about .7A on the 5v Line
and .55A on the 12v line.
So an External AC Plug Pack supplying 12v @ 1.5 to 2Amp should be adequate.
Be careful to match the polarity as marked on the back of your drive and use the correct thickness of the centre pin. There are 2-3 different sizes of this connector available at electronics component suppliers in case you make your own supply up.
Good Luck

Sep 08, 2014 | Verbatim SNS2TB Store n Save 2 Terabyte...

1 Answer

Lost my adapter of below drive

While I don't have any specific information about the drive in question.. I CAN tell you this:

MOST hardware works at 5v... Some (most) have an internal regulator to drove 9v or 12v back down to 5v... MEANING:

If this has your lost family's pictures on it, and its uber important to recover-- but you don't have the finacnes to purchase another to get the adaptor, etc..

START with a 5v adaptor.. move up to 9v..the eventually 12v... of course polarity is a concern (to not blow it up)... a multi-meter can fix that.

Ok.. thats the technical side.

EASY SIDE: Go but another... use the adaptor to get your stuff off.... return it... and get a new device.

Oct 16, 2012 | Samsung Pleomax (UHD6GB) Hard Drive

1 Answer

HELP locating 12v diode on Seagate ST3500820AS

For the answer you might look at

Sep 08, 2012 | Seagate Hard Drives

1 Answer

Hello. I have a LACIE EDMINI-V2 that won't start, no disk noises, no light from led in front button, nothing. I have dismantled the box, connected the disk drive to my PC and its ok, measured the 5V and...

I owned one just like this and the power supply failed at about 1 year. It turns out it's a fairly common problem. Since you have the device open, does the controlboard/motherboard look burnt at all?
If it is not damaged, you may be able to buy a replacement power supply here:
If it is damanged, then you may still be under manufacturer warranty, contact Lacie here: 503-844-4503
Please leave feedback for this answer, thanks.

Mar 09, 2011 | LaCie Ethernet Disk Mini, 500 GB Hard Disk...

2 Answers

External Hard Drive - Beyond Micro

I have the same BMMDU2. It's used 12V/1.5A power suply.

May 11, 2009 | Beyond Micro (BM120MD3U2) 120 GB USB 2.0...

1 Answer

Maxtor 90845D5 EIDE HDD jumper settings


Connected the 2 pins furthest away from the power connector.

Pin 1
J1 IDE Connector | J2 Power
+----------- --------+-++-----------++---------+
| .................... || @ * * * || X X X X |
| .......... ......... || @ * * * * || X X X X |
| | | | | | | | |
| | | | | | | | |
J50 Master/Slave -----+ | | | | | | | +-+12V
J48 Cable Select -------+ | | | | | +---+12V Return
J46 4092 Cyl Limitation---+ | | | +----- +5V Return
J44 Factory Reserved -------+ | +------- +5V
J42 Factory Reserved ---------+
Hope this helps.


Jun 28, 2008 | Maxtor Hard Drive

1 Answer

Shorted 12V on input to drive


Basically 2 options I think.
1. If you feel comfortable working with electronics, familiar with a DVM (looks like) and a soldering iron, it possible to check the electronic board of the HD. You need to do component level check of that PCB. Some of these old HDs have a reverse protection diode installed right after the power connector. At times it could be the surface mounted capacitor. The worst is the servo drive that powers the motor. Normally, the 12V in an HD is for use of the motor while the 5V is for the logic circuitry.

2. If you need to replace the HD, just about any hard drive should work for your PIII (just not the new big ones). Sources would be your neighborhood computer repair shops or a neighbor/friend who's got a defective PC and would probably just throw them away rather than have them repaired. You can salvaged the parts and hopefully a working HD. Most also would already have Win98SE and transition from one system to another in 98 would not be that much of a hassle. You can then use your original Windows key.

3. Should you get one that has no OS, you can use an OEM Windows installer and still use you original CD key.

Hope that this be of some help/idea. Pls post back how things worked out or should you need additional information.

Good luck and kind regards.

Dec 24, 2007 | Seagate U5 (ST320413A) 20 GB Hard Drive

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