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From: Man-wai Chang to The Door (33600bps) on 23 May 2010 09:20
This beast, with 2 USB ports (A-B) in its cable, draws a lot of power. I
found that most older PCs just can't power it. So I plan to buy a DC
power adaptor for it, as this beast has a DC in!

What approximate voltage & current should I look for?

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From: Paul on 23 May 2010 13:43
Man-wai Chang to The Door (33600bps) wrote:
> This beast, with 2 USB ports (A-B) in its cable, draws a lot of power. I
> found that most older PCs just can't power it. So I plan to buy a DC
> power adaptor for it, as this beast has a DC in!
>
> What approximate voltage & current should I look for?
>

You'd start by looking at the raw drive mechanism power specs.

Unfortunately, some of the drive manufacturers are dishonest, and
won't tell you the spinup current for their 2.5" drives. The current
can be in the 1 ampere range. Normal operating currents (once
the drive is spinning), will be less than that (0.5A or less).
So when a 2.5" drive refuses to work, it could be that it is
having trouble "spinning up".

I would buy a 5V @ 2A adapter, to have plenty of power. If one
was not available, I would buy a 5V @ 1A adapter. Anything with
less current rating than that, probably isn't worth having.

There are some sample specifications here. Only the "start-up" is
a problem. Any parameter below 2.5W is OK on a USB port hosted
right on the PC itself. This one is actually over the 1 amp mark
by a bit.

http://www.hgst.com/internal-drives/mobile/travelstar/travelstar-7k320

Start-up (W, peak, max) 5.5W which is the same as 5V @ 1.1 amps
Read/Write (W, avg) 1.8W
Low power idle (W, avg) 0.8W
Standby (W, avg) 0.2W

Having two power sources, with slightly different 5V values,
isn't really a good idea. I hope the barrel power jack
inside the disk drive enclosure, disconnects the USB bus power path,
when the AC adapter is in place. Otherwise, current could flow
from one 5V supply to the other.

Any adapter rated to provide more current than the "start-up" value,
should be sufficient. Even a 5V @ 1.5A adapter would do.

Paul
From: Man-wai Chang to The Door (33600bps) on 23 May 2010 23:21
> I would buy a 5V @ 2A adapter, to have plenty of power. If one
> was not available, I would buy a 5V @ 1A adapter. Anything with
> less current rating than that, probably isn't worth having.

5V @ 1A was also my guess...

> Having two power sources, with slightly different 5V values,
> isn't really a good idea. I hope the barrel power jack
> inside the disk drive enclosure, disconnects the USB bus power path,
> when the AC adapter is in place. Otherwise, current could flow
> from one 5V supply to the other.

Maybe all external disks should have a power switch! :)

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/ v \ Simplicity is Beauty! May the Force and Farce be with you!
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From: Man-wai Chang to The Door (33600bps) on 25 May 2010 05:35

Reply from Hitachi Support:

<quote>
Thank you for contacting Hitachi Global Storage Technologies.

The power supply requirements for the portable drive are as follows:
5Volts, 1Amp or greater, and Center Positive (Tip size: 3.4mm OD x1.3mm
ID). You can by this on any local computer or electronics shop.

Please let us know if we can be of further assistance.
</quote>

--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
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From: Arno on 25 May 2010 11:41
In comp.sys.ibm.pc.hardware.storage "Man-wai Chang to The Door (33600bps)" <toylet.toylet(a)gmail.com> wrote:

> Reply from Hitachi Support:

> <quote>
> Thank you for contacting Hitachi Global Storage Technologies.

> The power supply requirements for the portable drive are as follows:
> 5Volts, 1Amp or greater, and Center Positive (Tip size: 3.4mm OD x1.3mm
> ID). You can by this on any local computer or electronics shop.

> Please let us know if we can be of further assistance.
> </quote>

That should be enough info to get something suitable.
Arno
--
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