How can I measure correct polarity

I bought a Seagate USB harddrive in a case. It was on the bargain
shelf because it was missing the power supply module (transformer).
The plug is labelled 12VDC 2.0 A.

I have lots of these transformer modules since I bought a whole box of
them at an auction, and I have several 12VDC ones. One is a 4A, the
others are smaller. I'd almost expect the 1.5A ones that I have to
work also, because I know that harddrives do not use that much power.

Either way, the problem is the polarity. It has one of those common
center pin and side connectors that look like a target in a hole.
I know these are normally wired so the center pin is positive, bu
there are exceptions. I can easily measure the polarity of the module
output with my meter, but how can I measure the input of the harddrive
to determine which polarity is required?

Originally I intended to open it and look at the circuit board for
polarity markings, but they have it sealed with some sort of oddball
screws that look like a star with a pin in the middle. I've
considered drilling them out, if I can use a meter to determine the
polarity, that should be fine.

Anyone know how?

Thanks

LM

 

[Sjouke Burry]

letterman@invalid.com wrote:

I bought a Seagate USB harddrive in a case. It was on the bargain
shelf because it was missing the power supply module (transformer).
The plug is labelled 12VDC 2.0 A.

I have lots of these transformer modules since I bought a whole box of
them at an auction, and I have several 12VDC ones. One is a 4A, the
others are smaller. I'd almost expect the 1.5A ones that I have to
work also, because I know that harddrives do not use that much power.

Either way, the problem is the polarity. It has one of those common
center pin and side connectors that look like a target in a hole.
I know these are normally wired so the center pin is positive, bu
there are exceptions. I can easily measure the polarity of the module
output with my meter, but how can I measure the input of the harddrive
to determine which polarity is required?

Originally I intended to open it and look at the circuit board for
polarity markings, but they have it sealed with some sort of oddball
screws that look like a star with a pin in the middle. I've
considered drilling them out, if I can use a meter to determine the
polarity, that should be fine.

Anyone know how?

Thanks

LM


Check with a multimeter whether the outside part is connected

to ground.
If so, it uses +12v as centre.

 

[Franc Zabkar]

On Mon, 06 Apr 2009 18:01:24 -0400, letterman@invalid.com put finger
to keyboard and composed:

I bought a Seagate USB harddrive in a case. It was on the bargain
shelf because it was missing the power supply module (transformer).
The plug is labelled 12VDC 2.0 A.

I have lots of these transformer modules since I bought a whole box of
them at an auction, and I have several 12VDC ones. One is a 4A, the
others are smaller. I'd almost expect the 1.5A ones that I have to
work also, because I know that harddrives do not use that much power.

Either way, the problem is the polarity. It has one of those common
center pin and side connectors that look like a target in a hole.
I know these are normally wired so the center pin is positive, bu
there are exceptions. I can easily measure the polarity of the module
output with my meter, but how can I measure the input of the harddrive
to determine which polarity is required?

Originally I intended to open it and look at the circuit board for
polarity markings, but they have it sealed with some sort of oddball
screws that look like a star with a pin in the middle. I've
considered drilling them out, if I can use a meter to determine the
polarity, that should be fine.

Anyone know how?

Thanks

LM

Use a multimeter to test for continuity between the hard drive's +12V
power pin and the enclosure's power socket. Do the same for the ground
pin.

If it is a PATA drive, then the yellow power wire goes to +12V and the
black one goes to ground. Presumably the +5V supply is then generated
within the USB enclosure via a switchmode regulator.

If it is a SATA drive, then use this pinout diagram:
http://pinouts.ru/Power/sata-power_pinout.shtml

Be sure that your +12V supply is regulated. An unregulated supply may
damage the hard drive's Transient Voltage Suppression (TVS) diode.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

 

[Samuel M. Goldwasser]

letterman@invalid.com writes:

I bought a Seagate USB harddrive in a case. It was on the bargain
shelf because it was missing the power supply module (transformer).
The plug is labelled 12VDC 2.0 A.

I have lots of these transformer modules since I bought a whole box of
them at an auction, and I have several 12VDC ones. One is a 4A, the
others are smaller. I'd almost expect the 1.5A ones that I have to
work also, because I know that harddrives do not use that much power.

Either way, the problem is the polarity. It has one of those common
center pin and side connectors that look like a target in a hole.
I know these are normally wired so the center pin is positive, bu
there are exceptions. I can easily measure the polarity of the module
output with my meter, but how can I measure the input of the harddrive
to determine which polarity is required?

Originally I intended to open it and look at the circuit board for
polarity markings, but they have it sealed with some sort of oddball
screws that look like a star with a pin in the middle. I've
considered drilling them out, if I can use a meter to determine the
polarity, that should be fine.

The surest way would be provide the complete model number and then
someone who has one can check!

The next surest way would be to open and trace the input to the
disk drive power connector, of if is wired directly, to the
filter caps which will be labeled with polarity.

Those strange screws sound like "security Torx". You can get a
complete set of security screwdriver bits for those and many other
types of $5 or $10. Or, it is usually possible to simply break
off the center hib with a small screwdriver or other suitable tool.

However, if you check continuity between each side of the power socket
and ground of the USB connector, the one with 0 ohms would almsot
certainly be negative.

Normal disclaimers apply - I can't guarantee that Seagate didn't
do something totoally stupid and confusing!

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

 

On 06 Apr 2009 20:23:11 -0400, sam@repairfaq.org (Samuel M.
Goldwasser) wrote:

letterman@invalid.com writes:

I bought a Seagate USB harddrive in a case. It was on the bargain
shelf because it was missing the power supply module (transformer).
The plug is labelled 12VDC 2.0 A.

I have lots of these transformer modules since I bought a whole box of
them at an auction, and I have several 12VDC ones. One is a 4A, the
others are smaller. I'd almost expect the 1.5A ones that I have to
work also, because I know that harddrives do not use that much power.

Either way, the problem is the polarity. It has one of those common
center pin and side connectors that look like a target in a hole.
I know these are normally wired so the center pin is positive, bu
there are exceptions. I can easily measure the polarity of the module
output with my meter, but how can I measure the input of the harddrive
to determine which polarity is required?

Originally I intended to open it and look at the circuit board for
polarity markings, but they have it sealed with some sort of oddball
screws that look like a star with a pin in the middle. I've
considered drilling them out, if I can use a meter to determine the
polarity, that should be fine.

The surest way would be provide the complete model number and then
someone who has one can check!

Thanks - The model is
Seagate 3.5-inch External Storage Hard Drive
ST300003U2
It can be seen here:
http://tinyurl.com/d2fle8
I have the small one, the 80gig version.

While I did find a basic manual for it on this Seagate site, they
do not list the polarity, just the usual useless stuff, like how to
plug it in.....

The next surest way would be to open and trace the input to the
disk drive power connector, of if is wired directly, to the
filter caps which will be labeled with polarity.

That's what I wanted to do till I found those idiot screws.
There's no warranty for it anyhow.

Those strange screws sound like "security Torx". You can get a
complete set of security screwdriver bits for those and many other
types of $5 or $10. Or, it is usually possible to simply break
off the center hib with a small screwdriver or other suitable tool.

Yep, I have some torx drivers in the garage, like for auto taillight
lenses, but these would need a hole in the center. I guess that's the
"security" part..... I'll see if I can break out that center. I'll
replace the screws with standard phillips or slotted screws as soon as
they come out anyhow. I hate things like that where I need special
tools.

However, if you check continuity between each side of the power socket
and ground of the USB connector, the one with 0 ohms would almsot
certainly be negative.

I've never known what the pinout is for a USB connector, would the
ground be the metal shell around the outside?
(Do ya know of a website with a pinout, I may as well learn this).

Normal disclaimers apply - I can't guarantee that Seagate didn't
do something totoally stupid and confusing!

Seagate seems pretty lame anyhow, so I'd agree. It only took me 2
hours to find the webpage for this drive, because it said
"discontinued" everytime I entered the model #. I dont care if it's
discontinued, they made it, at least they could provide info on it in
an easy to find manner. I dont think it should be a big secret just
because they no longer sell them.

I hope I can get the driver from them. I have the url on that manual,
but I have not yet tried. I'm running Win98se so I need it.

By the way, I never used an external USB harddrive before. Will I
need to Fdisk, partition, and format it? I've done that many times on
internal drives, so I know how.

Thanks for the help.

LM

 

[Rich Webb]

On Mon, 06 Apr 2009 20:31:38 -0400, letterman@invalid.com wrote:

On 06 Apr 2009 20:23:11 -0400, sam@repairfaq.org (Samuel M.
Goldwasser) wrote:

letterman@invalid.com writes:

I bought a Seagate USB harddrive in a case. It was on the bargain
shelf because it was missing the power supply module (transformer).
The plug is labelled 12VDC 2.0 A.

I have lots of these transformer modules since I bought a whole box of
them at an auction, and I have several 12VDC ones. One is a 4A, the
others are smaller. I'd almost expect the 1.5A ones that I have to
work also, because I know that harddrives do not use that much power.

Either way, the problem is the polarity. It has one of those common
center pin and side connectors that look like a target in a hole.
I know these are normally wired so the center pin is positive, bu
there are exceptions. I can easily measure the polarity of the module
output with my meter, but how can I measure the input of the harddrive
to determine which polarity is required?

Originally I intended to open it and look at the circuit board for
polarity markings, but they have it sealed with some sort of oddball
screws that look like a star with a pin in the middle. I've
considered drilling them out, if I can use a meter to determine the
polarity, that should be fine.

The surest way would be provide the complete model number and then
someone who has one can check!


Thanks - The model is
Seagate 3.5-inch External Storage Hard Drive
ST300003U2
It can be seen here:
http://tinyurl.com/d2fle8
I have the small one, the 80gig version.

While I did find a basic manual for it on this Seagate site, they
do not list the polarity, just the usual useless stuff, like how to
plug it in.....

The next surest way would be to open and trace the input to the
disk drive power connector, of if is wired directly, to the
filter caps which will be labeled with polarity.

That's what I wanted to do till I found those idiot screws.
There's no warranty for it anyhow.

Those strange screws sound like "security Torx". You can get a
complete set of security screwdriver bits for those and many other
types of $5 or $10. Or, it is usually possible to simply break
off the center hib with a small screwdriver or other suitable tool.

Yep, I have some torx drivers in the garage, like for auto taillight
lenses, but these would need a hole in the center. I guess that's the
"security" part..... I'll see if I can break out that center. I'll
replace the screws with standard phillips or slotted screws as soon as
they come out anyhow. I hate things like that where I need special
tools.

Jeez, you can probably find a set of security bits at your local
hardware store, or Harbor Freight, Northern Tools, ... Also online at
<http://www.allelectronics.com/make-a-store/item/BT-33/33-PC-SECURITY-BIT-SET/-/1.html>
and many others.

Besides, if you're into this sort of thing (no pun intended), you might
enjoy browsing around the AllElectronics site.

--
Rich Webb Norfolk, VA

 

On Mon, 06 Apr 2009 21:46:02 -0400, Rich Webb
<bbew.ar@mapson.nozirev.ten> wrote:

On Mon, 06 Apr 2009 20:31:38 -0400, letterman@invalid.com wrote:

On 06 Apr 2009 20:23:11 -0400, sam@repairfaq.org (Samuel M.
Goldwasser) wrote:

letterman@invalid.com writes:

I bought a Seagate USB harddrive in a case. It was on the bargain
shelf because it was missing the power supply module (transformer).
The plug is labelled 12VDC 2.0 A.

I have lots of these transformer modules since I bought a whole box of
them at an auction, and I have several 12VDC ones. One is a 4A, the
others are smaller. I'd almost expect the 1.5A ones that I have to
work also, because I know that harddrives do not use that much power.

Either way, the problem is the polarity. It has one of those common
center pin and side connectors that look like a target in a hole.
I know these are normally wired so the center pin is positive, bu
there are exceptions. I can easily measure the polarity of the module
output with my meter, but how can I measure the input of the harddrive
to determine which polarity is required?

Originally I intended to open it and look at the circuit board for
polarity markings, but they have it sealed with some sort of oddball
screws that look like a star with a pin in the middle. I've
considered drilling them out, if I can use a meter to determine the
polarity, that should be fine.

The surest way would be provide the complete model number and then
someone who has one can check!


Thanks - The model is
Seagate 3.5-inch External Storage Hard Drive
ST300003U2
It can be seen here:
http://tinyurl.com/d2fle8
I have the small one, the 80gig version.

While I did find a basic manual for it on this Seagate site, they
do not list the polarity, just the usual useless stuff, like how to
plug it in.....

The next surest way would be to open and trace the input to the
disk drive power connector, of if is wired directly, to the
filter caps which will be labeled with polarity.

That's what I wanted to do till I found those idiot screws.
There's no warranty for it anyhow.

Those strange screws sound like "security Torx". You can get a
complete set of security screwdriver bits for those and many other
types of $5 or $10. Or, it is usually possible to simply break
off the center hib with a small screwdriver or other suitable tool.

Yep, I have some torx drivers in the garage, like for auto taillight
lenses, but these would need a hole in the center. I guess that's the
"security" part..... I'll see if I can break out that center. I'll
replace the screws with standard phillips or slotted screws as soon as
they come out anyhow. I hate things like that where I need special
tools.

Jeez, you can probably find a set of security bits at your local
hardware store, or Harbor Freight, Northern Tools, ... Also online at
http://www.allelectronics.com/make-a-store/item/BT-33/33-PC-SECURITY-BIT-SET/-/1.html
and many others.

Besides, if you're into this sort of thing (no pun intended), you might
enjoy browsing around the AllElectronics site.

I wont find them at any local hardware store. This is a rural area.
I'm lucky to find 1 1/2" roofing nails, because they only stock the
full INCH size to save on stock. I already know that I can get them
mailorder, if I want to wait 2 weeks before I can use this drive.
Around here, delivery is slow, and the Post Office always makes sure
to deliver a "pink slip" (item to pickup at the Post Office), late on
Friday, so I have to wait until Monday to get the item and then take
off of work an hour early because the P.O. has such limited hours.
I may order these for the future, but for now, busting those screws
out and spending half a dollar for four standard replacement screws
sounds like a much better option, and I'll never have to fight with
them again.

PS AllElectronics is a fun site to look at.

Thanks

 

On Tue, 07 Apr 2009 16:17:24 +1000, Franc Zabkar
<fzabkar@iinternode.on.net> wrote:

On Mon, 06 Apr 2009 20:31:38 -0400, letterman@invalid.com put finger
to keyboard and composed:

I hope I can get the driver from them. I have the url on that manual,
but I have not yet tried. I'm running Win98se so I need it.

Use the Maximus Decim NUSB generic mass storage driver set:
http://www.technical-assistance.co.uk/kb/usbmsd98.php

Thanks Franc
I see you're over on this NG too !!!!
I have that NUSB installed and it seems to work with everything except
those Sandisk flash sticks. But that's ok, I installed NUSB first,
then the Sandisk drivers. Do I need to install NUSB everytime I plug
in something new, or is it just there ready for anything?

Oddly enough I bought another IDENTICAL Sandisk flash stick and had to
install the Sandisk driver a second time, even if I replaced the new
stick with the old one. Now that's just plain weird.

By the way, I never used an external USB harddrive before. Will I
need to Fdisk, partition, and format it? I've done that many times on
internal drives, so I know how.

That's the way I did it, but from within a Windows DOS box, IIRC.

OK, I have Partition Magic too, I suppose that will also work. I know
I cant do it from regular Dos because it wont find the USB drive.

- Franc Zabkar

 

[Franc Zabkar]

On Mon, 06 Apr 2009 20:31:38 -0400, letterman@invalid.com put finger
to keyboard and composed:

I hope I can get the driver from them. I have the url on that manual,
but I have not yet tried. I'm running Win98se so I need it.

Use the Maximus Decim NUSB generic mass storage driver set:
http://www.technical-assistance.co.uk/kb/usbmsd98.php

By the way, I never used an external USB harddrive before. Will I
need to Fdisk, partition, and format it? I've done that many times on
internal drives, so I know how.

That's the way I did it, but from within a Windows DOS box, IIRC.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

 

[William Sommerwerck]

I just had an idea...

Try sticking your ohmeter -- specifically, with the diode test selected --
across the power-jack terminals, and measure the resistance in both
directions. I'm guessing that the lower resistance represents the correct
polarity. (Your ohmeter is probably + on the red lead, but this isn't always
true.)

 

[Rodney Pont]

On Mon, 06 Apr 2009 20:31:38 -0400, letterman@invalid.com wrote:

Thanks - The model is
Seagate 3.5-inch External Storage Hard Drive
ST300003U2
It can be seen here:
http://tinyurl.com/d2fle8
I have the small one, the 80gig version.

I've got one of them and the PSU label says centre +ve.

--
Regards - Rodney Pont
The from address exists but is mostly dumped,
please send any emails to the address below
e-mail ngpsm4 (at) infohitsystems (dot) ltd (dot) uk

 

[Smitty Two]

In article <hdukt4tshl1ono23vj4k3n2ld6egn0bfoh@4ax.com>,
letterman@invalid.com wrote:

I bought a Seagate USB harddrive in a case. It was on the bargain
shelf because it was missing the power supply module (transformer).
The plug is labelled 12VDC 2.0 A.

I have lots of these transformer modules since I bought a whole box of
them at an auction, and I have several 12VDC ones. One is a 4A, the
others are smaller. I'd almost expect the 1.5A ones that I have to
work also, because I know that harddrives do not use that much power.

Either way, the problem is the polarity. It has one of those common
center pin and side connectors that look like a target in a hole.
I know these are normally wired so the center pin is positive, bu
there are exceptions. I can easily measure the polarity of the module
output with my meter, but how can I measure the input of the harddrive
to determine which polarity is required?

Originally I intended to open it and look at the circuit board for
polarity markings, but they have it sealed with some sort of oddball
screws that look like a star with a pin in the middle. I've
considered drilling them out, if I can use a meter to determine the
polarity, that should be fine.

Anyone know how?

Thanks

LM

I don't know about hard drives, but every device I have that runs from a
wall wart, has a molded-in logo that identifies polarity. Hard to see at
my age without strong light and strong magnification, but it's always
been there.

Besides voltage and polarity, the other thing that's critical is the
center pin diameter. Easy to overlook if the outside contact is snug,
because you don't notice that the inside is loose.

 

On Tue, 07 Apr 2009 09:42:15 +0100 (BST), "Rodney Pont"
<pmmspamscop@infohitsystems.ltd.uk> wrote:

On Mon, 06 Apr 2009 20:31:38 -0400, letterman@invalid.com wrote:

Thanks - The model is
Seagate 3.5-inch External Storage Hard Drive
ST300003U2
It can be seen here:
http://tinyurl.com/d2fle8
I have the small one, the 80gig version.

I've got one of them and the PSU label says centre +ve.

Thanks !!!!!!!!!

That saves lots of screwing around and paranoia that I'd fry the
thing. I suspected the center was +, but some oddball things are
reversed, which never made much sense to me.

How do you like your drive? I've never used a USB drive so I wonder
how fast they are???

PS. Some guy on Ebay is selling the power supplies for them, or at
least that's what he claims they are for. I never trust ebay
electronics stuff. I'm sure any of mine should work, even the 1.5A
ones. I surely can not see it needing 2A for one HD. But I do have a
4A one too.

LM

 

On Tue, 07 Apr 2009 19:09:08 -0700, Smitty Two
<prestwhich@earthlink.net> wrote:

In article <hdukt4tshl1ono23vj4k3n2ld6egn0bfoh@4ax.com>,
letterman@invalid.com wrote:

I bought a Seagate USB harddrive in a case. It was on the bargain
shelf because it was missing the power supply module (transformer).
The plug is labelled 12VDC 2.0 A.

I have lots of these transformer modules since I bought a whole box of
them at an auction, and I have several 12VDC ones. One is a 4A, the
others are smaller. I'd almost expect the 1.5A ones that I have to
work also, because I know that harddrives do not use that much power.

Either way, the problem is the polarity. It has one of those common
center pin and side connectors that look like a target in a hole.
I know these are normally wired so the center pin is positive, bu
there are exceptions. I can easily measure the polarity of the module
output with my meter, but how can I measure the input of the harddrive
to determine which polarity is required?

Originally I intended to open it and look at the circuit board for
polarity markings, but they have it sealed with some sort of oddball
screws that look like a star with a pin in the middle. I've
considered drilling them out, if I can use a meter to determine the
polarity, that should be fine.

Anyone know how?

Thanks

LM

I don't know about hard drives, but every device I have that runs from a
wall wart, has a molded-in logo that identifies polarity. Hard to see at
my age without strong light and strong magnification, but it's always
been there.

Besides voltage and polarity, the other thing that's critical is the
center pin diameter. Easy to overlook if the outside contact is snug,
because you don't notice that the inside is loose.

Mine has a molded image near the plug that is a circle with a line
sticking out one side. But no + or - on it. (What's the point to
that)? I did use my best eye glasses too....

Yea, I know, there are wayyyyyyyy to many of those plugs. All they
ever needed was 2 sizes, large and small. But that would be too
practical and sensible..... The idea is to make everything as
complicated and confusing as possible.....

LM

 

[Rodney Pont]

On Wed, 08 Apr 2009 04:29:52 -0400, letterman@invalid.com wrote:

How do you like your drive? I've never used a USB drive so I wonder
how fast they are???

It does it's job but drives aren't something I get attached to. I
wouldn't call it fast, USB is a lot slower than internal SATA II

PS. Some guy on Ebay is selling the power supplies for them, or at
least that's what he claims they are for. I never trust ebay
electronics stuff. I'm sure any of mine should work, even the 1.5A
ones. I surely can not see it needing 2A for one HD. But I do have a
4A one too.

I'd try it with the 4A one first and time how long it takes to come
ready. Then do the same with the 1.5A one. They can take a fair bit of
power to spin up and if 1.5A isn't enough it may not come ready if it
pulls the voltage down too much.

--
Regards - Rodney Pont
The from address exists but is mostly dumped,
please send any emails to the address below
e-mail ngpsm4 (at) infohitsystems (dot) ltd (dot) uk