Hey Kony,

I really appreciate your answers and advices.
I uploaded 2 pictures of the 2 harddiscs, in case somebody wanna take
a look.
http://picasaweb.google.de/borat.gunter/Harddisc#

I just looked after "schottky diode 5v'" at digikey.com.
http://search.digikey.com/scripts/Dk...hottky%20diode

here comes the question again. What I am pretty sure is i need a 5v
not a 12v diode. plus SOD as a must.
But other parameters I have no idea at all. I have no idea how big the
current flow to the subcircuit. and
how big should the capacitor be for esd reason.

Is there anyway that I can learn how to decide this. How does the pcb
designer make their choice? It has to be some rules, or tutorials. or
we just know it.

Best

Borat
On 18 Dez., 17:20, kony <s...@spam.com> wrote:
> On Thu, 18 Dec 2008 07:47:39 -0800 (PST), "borat.gunter"
>
>
>
> <borat.gun...@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.