Did I fry my external drive?

[chihlidog]

I plugged in the wrong adapter tip on my WD MyBook. I think I am missing the correct adapter, so I went to Radio Shack, and asked if they had an adapter for it. We tried a bunch of different tips, but it isnt powering on. Is it possible I fried it by plugging in the wrong adapter for less than a second?

 

[RetiredChief]

External HDDs come in two flavors, the 3 1/2 in which reguires a +12 V adaptor (Brick) and the 2 1/2 in HDDs which require a +5 V brick.

So if your my book has the 2 1/2 in HDD and you pluged a +12 V brick in to it, YES you have probably fried either the internal interface (circuitry between the HDD and the Plug) and/or the HDD. If you used the correct brick but only changed the tip/plug end) then A smaller possibility is that you revearsed the polarity - Same results)

Determine which HDD is inside the My Book and look at the Brick you used - If HDD is 2 /12 In (Laptop size) and brick was a +12 V output. Then, If still under warrenty I would try an RMA (They may not honor the warrenty as "USER damaged). You could also dissasemble the the My book (Voilds Warrenty) remove the HDD and try the HDD by itself, or get a cheap enclosure and try.

 

[chihlidog]

OK, I just pulled the thing apart and tried to use it like an internal. As soon as I plugged it in to the PCs power supply, the computer shut down. I'm thinking that this is just an issue of the power supply on this machine (I'm at work so it's not my machine and isnt very strong) not being able to power it.

Is there any way that it would actually shut the PC down if it was fried? I would think the drive simply wouldnt work if it's dead, not shut the rest of the PC down. Am I missing something??

Chief, I really appreciate your input on this one. It's a regular 3.5 drive, I know from WD that it needs a 12v adapter. Looking at the adapter I put into it, it's a lot more than that.

 

[RetiredChief]

Yes it is possible to "shut the PC Down" when plugged in. It's possible that the Power input circuitry is shorted and would cause an over load on the +12 V rail.

On +12 V bricks, The true output is often much higher than +12 V, some times as High as +19 V and is dependent on the load current/Rating.

You did power the computer down before attaching the HDD and then power up the PC.

3 1/2 in HDDs use both the +5 and +12 V Railes. When installed into an external enclosure and powered by a brick, the input circuitry of the encloser derives the +5 from the +12 V.

 

[chihlidog]

I didnt shut down at first. I just wanted to see if it would spin, so I hooked it up to the power supply. I know, Im not very smart today. I was just sort of panicking. But when it shut down, I then powered the PC back up (everything's OK, I am posting from it), did a proper shut down, and connected the drive. Wouldnt power on for more than a split second with the drive connected.

I really appreciate the input on this, RC. I'm an IDIOT today.

 

[fzabkar]

Most adapters these days are switchmode types, which means they are regulated, ie their output voltage doesn't vary with the load.

Since you say that your drive uses a 12VDC adapter, then the most likely culprit is a shorted TVS diode on the +12V rail. You can simply remove this component with flush cutters.

Assuming there is no other damage, the drive will work perfectly well without the diode, but it will no longer have overvoltage protection on the affected supply. So be absolutely certain your power supply is good.

If, for continued protection, you wish to replace the diode, then a 5V TVS diode can be substituted with an SMAJ5.0A, and a 12V diode with an SMBJ12A. Both can be ordered from Farnell, Mouser, Digikey.

These URLs should help you identify the components:

http://hddscan.com/doc/HDD_from_inside.html
http://www.users.on.net/~fzabkar/HDD/HDD_ICs.txt
http://www.users.on.net/~fzabkar/HDD/TVS_diodes.txt

If you need more help, then upload a detailed photo of the component side of the PCB.

 

[RetiredChief]

+1 ^ good post.
What Fzabkar provided is a very good possibility that is that the TVS (Transit voltage Protection) diode is shorted. The normal function of this diode is to protect against voltage spikes which are very short duration and does not destroy the diode, but if the overvoltage last for too long then the diode will be destroyed resulting in a short. This diode also will normally protect against reverse voltage (acts like any other forward biased diode), but in this case it is also distorted (ie shorted). In some cases this short, depending on the power supply current capabilities, and how long the voltage is applied may “burn” the diode open in which case other components will be destroyed.

If you know how to use a DVM (cheap ones are available at radio shack and automotive stores. Then if you can ohms check the input power. Measure it with the Black lead connect to one side of the power, red lead to the other side. Then repeat by reversing the meter leads. One way should be high resistance and the revered connection should be a lower resistance. Low Resistance both ways indicates a shorted diode. If this is the case then Fzabkar’s first link may be used to locate the diodes.

Fzabkar. While I would concur that most Switching Power supplies provide regulation such as Computer PSUs, Many of the “cheaper” power adaptors (generally above two amps) omit the “regulator” circuit and use a fixed Pulse width modulation (gee who would suspect manuf to cut cost) and rely on the device that is being powered to provide the regulation. For cheap Adaptors below two amps, a simple step down transformer, rectifier and filter are often used and as long as the current rating is not exceeded the output is acceptable.