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polarity of power cord - gateway fpd1520

 
 
zirath
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      03-28-2008, 08:45 AM
We recently got a gateway fpd1520 (15" lcd flatscreen) monitor from
ebay. It didn't have a power cord. It says it's a 12v dc 2.5a but it
doesn't give the polarity. A person from gateway said he thought it
wouldn't hurt the monitor if it got plugged in backwards but I'd rather
not try it.

Would appreciate any help.
 
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Arfa Daily
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      03-28-2008, 09:50 AM

"zirath" <(E-Mail Removed)> wrote in message
news:0f2Hj.7616$Yy2.1091@trndny04...
> We recently got a gateway fpd1520 (15" lcd flatscreen) monitor from ebay.
> It didn't have a power cord. It says it's a 12v dc 2.5a but it doesn't
> give the polarity. A person from gateway said he thought it wouldn't hurt
> the monitor if it got plugged in backwards but I'd rather not try it.
>
> Would appreciate any help.


If it has got any external metal parts such as RCA (phono) connector outers,
BNC connector outers, 'D' connector surround etc, or possibly screws for a
stand, as these often go right through the plastic case, and into the
internal chassis, then try measuring from any such metal to each of the DC
power input connector's terminals in turn, using an ohm meter. Chances are
you'll find a direct connection, and that will be your DC ground ( "-" )
connection. The other will then be the "+". Assuming that it's a 'standard'
co-axial DC connector, on most modern equipment, 'pin' is "+" and side
contact is "-" although that's not cast in stone. Be aware when you are
obtaining a replacement PSU, that the plug is often a slightly abnormal
size, being a little larger than those you typically find on 'general' power
supplies. Also, make sure that you get one well rated for the job, as these
monitors do draw quite a lot of current, and may well surge up close to the
quoted 2.5 amps at startup, as the LCD backlights first fire up before
settling to their run current.

As to whether it would be safe to reverse connect it, I wouldn't like to
say. Some equipment is perfectly well protected against such 'consumer
antics', but it is by no means guaranteed, and if it is not adequately
protected, the result is often an item that's fried beyond repair, for no
other reason than unobtainable power supply devices, as many previous posts
on this subject over the years, will attest ...

Arfa


 
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Arfa Daily
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      03-28-2008, 12:52 PM

"William Sommerwerck" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed). ..
> "Arfa Daily" <(E-Mail Removed)> wrote in message
> news:Wb3Hj.18668$(E-Mail Removed)...
>
>> If it has got any external metal parts such as RCA (phono) connector
>> outers, BNC connector outers, 'D' connector surround etc, or possibly
>> screws for a stand, as these often go right through the plastic case,
>> and into the internal chassis, then try measuring from any such metal to
>> each of the DC power input connector's terminals in turn, using an ohm
>> meter. Chances are you'll find a direct connection, and that will be your
>> DC ground ( "-" ) connection. The other will then be the "+".

>
> Arfa, you're usually dead-on, but this is quite incorrect. The side of the
> connector that's "grounded" is not necessarily negative! A transistor
> radio
> using PNP transistors would (presumably) have a positive ground, not
> negative.



I think you'll find that on 'most' modern - and I did say "modern" in my
original reply - equipment, this has been pretty much standardised such that
DC "-" *is* common ground. Sony kit that I have seen in recent years has all
obeyed this 'convention', so I'm willing to bet that any Sony items that
follow the opposite 'convention', are not "modern". Pin = "-" used to be the
'convention', but for all mainstream manufacturers whose equipment I work
on, this has not been the case for many years. It was only usually the
Japanese manufacturers that followed this anyway, as I recall.

As for a transistor radio that uses PNP transistors, I haven't seen one that
uses transistors at all for many years, let alone PNP ones, so I think you
might be struggling to fit that into my "modern" category, also.


>
>
>> Assuming that it's a 'standard' co-axial DC connector, on most modern
>> equipment, 'pin' is "+" and side contact is "-" although that's not cast

> in
>> stone.

>
> No, it's not. I have Sony equipment where the pin is negative, not
> positive.
>
>
> Rather than seeing which side of the power connector is grounded, I would
> look to see which side of the electrolytic capacitors is grounded.
>


This is, of course, the very best way, if the owner wants the trouble of
taking it all to bits, and identifying a suitable electrolytic to use as his
reference. However, I would put my name on the line that the method I quoted
before, would 99.5% yield the same result, with any 'modern' item using a
coaxial DC socket. Perhaps someone out there with a Gateway monitor could
confirm which way round it is, then neither of us will be applying guesswork
to experience and coming up with sage advice ... d;~}

Arfa


 
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BillW50
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      03-28-2008, 01:36 PM
In news:KS5Hj.22783$(E-Mail Removed),
Arfa Daily typed on Fri, 28 Mar 2008 12:52:58 GMT:
[...]
> As for a transistor radio that uses PNP transistors, I haven't seen
> one that uses transistors at all for many years, let alone PNP ones,
> so I think you might be struggling to fit that into my "modern"
> category, also.


Well Arfa... they still use transistors (both NPN and PNP types) in
modern equipment. The reason you don't see them anymore is do to the
magic of minturization. But they are still there, just neatly packaged
into what is known today as the intergrated circuit (IC chip).

--
Bill

 
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Arfa Daily
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      03-28-2008, 04:07 PM

"BillW50" <(E-Mail Removed)> wrote in message
news:47ecf425$0$1345$(E-Mail Removed). com...
> In news:KS5Hj.22783$(E-Mail Removed),
> Arfa Daily typed on Fri, 28 Mar 2008 12:52:58 GMT:
> [...]
>> As for a transistor radio that uses PNP transistors, I haven't seen
>> one that uses transistors at all for many years, let alone PNP ones,
>> so I think you might be struggling to fit that into my "modern"
>> category, also.

>
> Well Arfa... they still use transistors (both NPN and PNP types) in modern
> equipment. The reason you don't see them anymore is do to the magic of
> minturization. But they are still there, just neatly packaged into what is
> known today as the intergrated circuit (IC chip).
>
> --
> Bill

And I though I was pedantic !! Yes, of course ICs contain transistors, and
yes, I would accept that some of them may be PNP types, depending on block
function within the IC, but I don't think, with the best will in the world,
that this is the level of transistor existence that William was referring to
with his "transistor radio using PNP transistors" scenario. In any event, in
the case of an IC taking a single polarity rail, it is irrelevant whether
the transistors inside are NPN or PNP or FETs or whatever. PNP transistors
are just used 'upside down', as are discrete PNP transistors when used in
any piece of single polarity rail equipment. The ground is still (typically
for //modern// equipment) the "-" side of the power supply / battery.

Anyway, this is getting out of hand. The OP aked a simple question, and I
gave a simple answer. This afternoon, I was in a friend's computer repair
shop. Bear in mind that he deals with monitors of all types and makes on a
daily basis. I asked him how he would go about determining the polarity of
such a monitor, and he said that he would stick one side of his ohm meter on
one of the D connector locking screws, and the other on each pin of the DC
connector. When he found the pin that read short to the connector locking
screw, it was his contention that he would have identified the "-" side of
the power supply. So that's pretty much exactly what I said. He also frowned
and shook his head, and said that he couldn't remember how many years it had
been since he had seen a DC connector that had the pin as the "-".

Which is also pretty much what I said ...

Arfa


 
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dirskyster@gmail.com
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      03-28-2008, 07:09 PM
On 3月28日, 下午4时45分, zirath <(E-Mail Removed)> wrote:
> We recently got a gateway fpd1520 (15" lcd flatscreen) monitor from
> ebay. It didn't have a power cord. It says it's a 12v dc 2.5a but it
> doesn't give the polarity. A person from gateway said he thought it
> wouldn't hurt the monitor if it got plugged in backwards but I'd rather
> not try it.
>
> Would appreciate any help.




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Arfa Daily
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      03-29-2008, 01:53 AM

"James Sweet" <(E-Mail Removed)> wrote in message
news:kjhHj.461$oE1.370@trndny09...
>
>
> "William Sommerwerck" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed). ..
>>> On the monitor it should be marked or say something
>>> in the manual.

>>
>> "The Lady from Philadelphia" forgot the obvious. Power sockets almost
>> always
>> have their polarity marked.
>>
>>

>
> I've certainly seen plenty of them that didn't though.
>

Likewise

Arfa


 
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James Sweet
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      03-29-2008, 01:54 AM


"William Sommerwerck" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed). ..
>> On the monitor it should be marked or say something
>> in the manual.

>
> "The Lady from Philadelphia" forgot the obvious. Power sockets almost
> always
> have their polarity marked.
>
>


I've certainly seen plenty of them that didn't though.


 
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dirskyster@gmail.com
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Posts: n/a
 
      03-29-2008, 08:37 PM
On 3月28日, 下午4时45分, zirath <(E-Mail Removed)> wrote:
> We recently got a gateway fpd1520 (15" lcd flatscreen) monitor from
> ebay. It didn't have a power cord. It says it's a 12v dc 2.5a but it
> doesn't give the polarity. A person from gateway said he thought it
> wouldn't hurt the monitor if it got plugged in backwards but I'd rather
> not try it.
>
> Would appreciate any help.




Do you want access to China's massive pool of electronic
manufacturers... but lack the time to contact suppliers, negotiate
contracts, arrange shipping or monitor product quality? Don't worry -
Let seriouswholesale deal with all that for you.

*Check out the huge range of Gadgets, MP3 / MP4 Players, Car DVD /
Audio, and Computer Accessories now by visiting the online wholesale
catalog at seriouswholesale. com You'll have peace of mind thanks to
the seriouswholesale Quality Control, 12-month Warranty on all
products, and easy secure payment by credit card through Paypal.

Selling on eBay or your own online store? Send products direct from
our warehouse to your customers using our unique drop-shipping
service. You can profit by selling hundreds of different products,
without holding any of your own inventory! Any questions you have will
be answered by the seriouswholesale English-speaking customer support
team... Their aim is to make your China electronics importing business
easier to run than ever before.

Welcome to http://www.seriouswholesale.com.

seriouswholesale - Buy from the source, profit without the hassle.

- 12 Months Warranty - No minimum order restrictions - Drop-shipping
with no additional fee - Pay by safely by PayPal seriouswholesale
Wholesale Co., Ltd.: Chinas original and best online electronics
wholesaler & drop-shipper: seriouswholesale. com












 
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zirath
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      03-30-2008, 12:10 AM
zirath wrote:
> We recently got a gateway fpd1520 (15" lcd flatscreen) monitor from
> ebay. It didn't have a power cord. It says it's a 12v dc 2.5a but it
> doesn't give the polarity. A person from gateway said he thought it
> wouldn't hurt the monitor if it got plugged in backwards but I'd rather
> not try it.
>
> Would appreciate any help.


Thanks to everyone for your help.
 
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