On Thu, 18 Dec 2008 07:47:39 -0800 (PST), "borat.gunter"
<borat.gunter@googlemail.com> wrote:

>Hello folks,
>
>I have been busy. Now i wanna give a feedback to my previous question.
>
>After reading you guys's suggestion. I decided to resolder the diode
>which came from another new harddisc.
>
>And it works out, which means the diode does protect the circuit
>afterward, of course my friend has to sacrifice her new harddisc.
>
>I have no idea what kind of type diode can be used. I suggested her to
>look after a used one on ebay, so that her new one can be "repaired"
>as well.
>For now she is more than happy for having her baby photos again.
>Thanks for your guys.
>

What specs are required for the diode depends on where it
is, in which subcircuit. If it were only polarity
protection on the power input, just about anything that's
the right physical size would work.

if it's in a switching regulation circuit, an ultrafast
silicon or schotty would be desired.

Schottky would be the best, most compatible choice, since
the main limit in this use for schottky is their lower
voltage but there is no high voltage on a hard drive that
would exceed the typical schottky voltage ranges.
Therefore, pick a schottky that is the same physical size so
it can be soldered onto the pads where the old one was, and
rated for over 12V which almost all are. With that size and
the lowest voltage you can find above 12V, it should also be
capable of enough current.

Potential sources for it include Digikey, Mouser, Allied
Electronics, Newark, et al. Digikey would be among the most
expensive since they have a minimum order fee which AFAIK is
still $5, more than double what the diode probably costs.
You might also find one at an electronics surplus 'site
somewhere but not so much with surface mount parts. You
might also ask at a local electronics repair shop as they
might have some. Places like Radio Shack are not likely to
have any.