Schematic of Hard disc pcb

[borat.gunter]

Hallo
one friend just plug the 4 pin power connector in the wrong way to her
hard disc.
It seems that the part which is used to protect the over voltage has
been burn-off.
I am gonna change the part which is "physical" broken and back up her
data.

i wrote down the label on the component as
AE VU
GP804
it has only 2 pins.

I googled around, did not find the part datasheet.
has anyone idea or reference of the schematic which is used for the
hard dics pcb power protection?

Thanks a lot

Borat

 

[Gerard Bok]

one friend just plug the 4 pin power connector in the wrong way to her
hard disc.
It seems that the part which is used to protect the over voltage has
been burn-off.
I am gonna change the part which is "physical" broken and back up her
data.

i wrote down the label on the component as
AE VU
GP804
it has only 2 pins.

I googled around, did not find the part datasheet.
has anyone idea or reference of the schematic which is used for the
hard dics pcb power protection?

Tricky business
But on the bright side: If the part is indeed an overvoltage
protection device (which I doubt) going into 'permanent
protection mode' (i.e. short circuit) you could simply cut one of
it's wires.
As the drive is likely to be toasted anyway, this will either get
the drive working for a while or will otherwise do no further
harm.

 

[borat.gunter]

Tricky business
But on the bright side: If the part is indeed an overvoltage
protection device (which I doubt) going into 'permanent
protection mode' (i.e. short circuit) you could simply cut one of
it's wires.
As the drive is likely to be toasted anyway, this will either get
the drive working for a while or will otherwise do no further
harm.

I have asked my friend to take a picture. will follow up
But I am curious about the schematic part of such circuit. How does
the subcirciut work. No only in oder to fix it, more like the
principle.
I was thinking that the burn component were a fuse-like thing, which
would be sacrificed in order to protect the parts behind.

After discussing with my co-worker I think the hardware vendor would
pay more attention or effort on fuse-like component, since the
connector alone is really hard enough to connecte in the reverse way
which my friend did. I can't do that on my pc ;-(

Any schematic reference would be really helpful.
Thanks

 

[Gerard Bok]

But I am curious about the schematic part of such circuit. How does
the subcirciut work. No only in oder to fix it, more like the
principle.

The principle is easy.
You have your +12 volt which is used for the motor only.
(Correct me if I'm wrong.) You won't hurt the motor circuit with
5 volt.
And you have your +5 volt for the logic. 'Logic' are the parts
that will usually explode rather spectacular if exposed to
voltages over 7 or 8 volt.

I was thinking that the burn component were a fuse-like thing, which
would be sacrificed in order to protect the parts behind.

That would make sense. Were it not that such a circuit would add
a dime to the manufacturing costs

After discussing with my co-worker I think the hardware vendor would
pay more attention or effort on fuse-like component, since the
connector alone is really hard enough to connecte in the reverse way
which my friend did.

It would require both a fuse and a pretty big zener type diode.
Practically, this goes by the name crowbar and is implemented
using a fuse, a zener diode and a thyristor. Common in a PSU but
I've never seen them on harddisk controller boards.

Any schematic reference would be really helpful.

Sorry. The most recent schematics on harddisk I have at hand are
probably 20+ years old.

 

[borat.gunter]

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.

 

[borat.gunter]

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/DkSearch/dksus.dll?Cat=1376383&keywords=5v schottky diode

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

 

[david huan]

yeh.
that was what i did at the beginning,
VU GP804 AE is on the package.
but I didnt find anything similar to this decription.
That is the reason why I was digging deeply in order to figure out
which component it is.
Otherwise it would be too simple. ;-)

 

[borat.gunter]

A diode's voltage rating is the maximum it is guaranteed to
withstand.  Unless it is a zener diode you want the voltage
rating to be above the voltage at that point in the circuit.
By knowing the circuit, that is how they chose the component
value to use.

Since you have the diode from another hard drive circuit
board, get out a magnifying glass and read the codes off of
it and either go to the manufacturer's website or search for
them here to find out it's specs:http://alldatasheet.com/

I did it first. But the info on the package was not so useful.
it is "VU gp802 AE"
I googled around, found nothing about this