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So I've lost the adapter that came with my external HDD enclosure, but I have a pile of AC adapters, most are under-powered. This one is the closest, but it seems like the enclosure needs a little more amperage than the adapter would provide. Would it be safe to give it a try?

I've posted links to the specs on the HDD box, and the adapter I've found.

The HDD's power adapter specs are: [Specifications 1]

AC input 100~140V, DC output 12V 2.0A

My spare adapter shows: [Specifications 2]

Input 120VAC 60 Hz 27.1W / Output 12VAC 1670 mA

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Under no circumstances can you use this adaptor with the hard disk unit which requires DC (direct current) not AC (alternating current)! –  Julian Knight Jul 19 '12 at 22:25
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3 Answers

In general, an adapter rated close to the desired output is fine.

In fact, if the device is less than about a decade old, the truth is it generally doesn't matter all that much because most electronics are now made for the world market and have to put up with very widely varying inputs so they can handle pretty variable outputs.

A couple of issues though:

  • "Output 12VAC", is that a typo because it looks like the output is AC not DC, if that is true, you MUST NOT use it.
  • As the output is only rated 1.6a, it may not actually give that output especially if the device draws a full 12v, this may have a small long term impact on the reliability of the disk. This is offset by the fact that the device claims to want 24w (12v*2a) which is well within the 27w of the adaptor. So you should be OK.
  • If the device really draws 2a (actually it probably wont but its hard to predict), the adaptor is likely to run very hot
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No, that's not a typo. VAC means exactly what you thought it means: the output is AC (alternating current). This kind of power adapter is commonly used in stuff like ADSL models and wireless routers, but it should not be used with pure DC equipments like hard disks. –  billc.cn Jul 19 '12 at 22:24
    
Ha! Thanks, I've seen the picture now. Thanks for the edit. –  Julian Knight Jul 19 '12 at 22:26
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you must NOT use that adapter.
1] Voltage must be DC out @ 12 V or you will break things.

2] polarity of the plug C- for negitive center or C+ for positive center. Polarity

It is often on the plug and some times on the body of the ac adapter some times also on the device. but polarity needs to be kept you could burn things out if you have it reversed.

3] 1.6a is not what its rated for go for 2A and above. that amp rating is the maximum that adapter can handle. like house wiring plug to much draw over its max and a fire could happen.

on the other side depending on what drive is currently in the enclosure it may not need that much. many 3.5 drives though do indeed draw 2a as they start spinning. roughly 25 watts to start up and then as low as 4-7 watts while in normal use. the electronics and any fans in the enclosure would add a few watts to that. If it has a 2.5 replacemtn drive in it though it may only need 15 watts to start and as little as 2 Watts to run.

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You will need an adapter with at least that much current output unless the stock adapter has more current output than the hdd actually needs. You can use a higher amount of current but it is not good to have less. Here is a question about laptop charging but the voltage/current concepts should still hold true: http://superuser.com/a/172259/142485 .

As far as:

Would it be safe to give it a try?

No, you will need an adapter with DC output rather than AC.

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When you say 1670 amps, you mean milli-amps, right? 1.67 amps? –  Ethan Jul 19 '12 at 20:52
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I think the AC/DC mismatch trumps everything else. –  Daniel R Hicks Jul 19 '12 at 22:40
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