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Computer power supply question

 
 
j
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      06-24-2007
I bought a computer at a garage sale that was brought over from the United
Kingdom. Everything looks normal except that the power supply has a label
that says "230 volts". The AC power connector socket going into the back of
the power supply is the same shape as that of an american computer. The
power supply does not have a switch to switch from 120 to 230 volts like
many computer power supplies have. I would like to use the computer but I
cannot power it up from the AC wall socket due to the voltage difference. I
would like to take the power supply from my Dell computer and install it
into the computer that came from the UK. I looked, and both the Dell
computer and the UK computer have the same wiring and plugs coming out of
their power supplies except that the 20 pin connectors that plug into the
motherboard have different colored wires. Does it matter that the wires are
different colors? Is it ok to install the Dell power supply into the
computer from the UK? The UK computer is much fancier than my current
computer but I do not want to burn something up. I do know that the power
plugs that plug into the hard drive and CD and floppy are the same shape and
colors (red/yellow/black) on both power supplies. It is only the 22 pin
connectors that plug into the mother boards that have different colors,
although they are shaped the same. Thank you.


 
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babaloo
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      06-24-2007
Dell uses proprietary power supplies and they change the wiring in the
connector from the standard.
This has bedevilled many Dell owners.
An inexpensive ATX power supply is a better alternative.


 
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j
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      06-25-2007
Thanks for that information.

"babaloo" <(E-Mail Removed)> wrote in message
news:wxCfi.7084$(E-Mail Removed) t...
> Dell uses proprietary power supplies and they change the wiring in the
> connector from the standard.
> This has bedevilled many Dell owners.
> An inexpensive ATX power supply is a better alternative.
>
>



 
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Paul
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      06-25-2007
j wrote:
> I bought a computer at a garage sale that was brought over from the United
> Kingdom. Everything looks normal except that the power supply has a label
> that says "230 volts". The AC power connector socket going into the back of
> the power supply is the same shape as that of an american computer. The
> power supply does not have a switch to switch from 120 to 230 volts like
> many computer power supplies have. I would like to use the computer but I
> cannot power it up from the AC wall socket due to the voltage difference. I
> would like to take the power supply from my Dell computer and install it
> into the computer that came from the UK. I looked, and both the Dell
> computer and the UK computer have the same wiring and plugs coming out of
> their power supplies except that the 20 pin connectors that plug into the
> motherboard have different colored wires. Does it matter that the wires are
> different colors? Is it ok to install the Dell power supply into the
> computer from the UK? The UK computer is much fancier than my current
> computer but I do not want to burn something up. I do know that the power
> plugs that plug into the hard drive and CD and floppy are the same shape and
> colors (red/yellow/black) on both power supplies. It is only the 22 pin
> connectors that plug into the mother boards that have different colors,
> although they are shaped the same. Thank you.
>


As Babaloo said, a certain range of years of Dell computers, use custom
designs that are not normal. If you installed one of those Dell power
supplies, you could ruin the more standards based UK computer.

You can use the DC rail ratings and total power printed on the side
of the UK computer's power supply label, as a basis for shopping for
a new standard supply. (Open the computer and have a look at the label.)
The new supply you use, has to have at least the same or more ampere
capacity on each output, to be useful in the UK computer.

ATX power supplies have changed a bit, over the last few years. They
had 20 pins and had no 2x2 connector for the processor. The 20 pin in
that case may have had -5V available as well. Some computers also
had a 1x6 connector with extra 3.3V amongst other things, and that
helped with higher power AGP cards. The -5V was eventually removed
in later versions of supply standard. The 2x2 12V processor power
connector was added. And finally, the power supply went to 24 pins
on the main, again with the objective of adding more power, this
time for the PCI Express generation. Your computer could be from
any one of those generations, but more likely the first two, than the
most recent one.

These three specs capture those variations. You can read these docs
and compare to what you see inside the UK computer.

http://web.archive.org/web/200304240...12V_PS_1_1.pdf
http://www.formfactors.org/developer...X12V_1_3dg.pdf
http://www.formfactors.org/developer...public_br2.pdf

The Dell may have some similar looking connectors, but the colors
on the Dell are wrong. More recent Dells are interchangeable with
stuff you can find at the computer store. There was a range of
model years that were non-standard.

This one comes pretty close to being a universal replacement for
some older computers. The label shows this one still carries -5V,
so that helps the older computers work. (You'd want to verify that
the model you buy, still lists that on the label, if you feel that
is important in your case.) The 5V at 32A makes it suitable for
some of the Athlon computers that powered the processor from the
5V rail. The 12V rating of 26A is generous, considering a cheap
P4 computer's requirements start at around 15A, and the power
supply has the necessary 2x2 ATX12V connector, with two yellow and
two black wires.

+3.3V @ 32A, +5V @ 32A, +12V @ 26A, -5V @ 1A, -12V @ 1A, +5VSB @ 2.2A
http://images10.newegg.com/NeweggIma...194-014-04.jpg

You can see the wiring in this picture.
http://images10.newegg.com/NeweggIma...194-014-05.jpg

The "CPU power" is the 2x2 ATX12V for the processor. There is also
a 20+4 shown for the main power connector. That means you see a 24pin
connector when you open the box the power supply comes in. If the
motherboard on your computer has a 20 pin connector, you slide off
the extra 4 pins, as it detaches. That is where the 20+4 description
comes from, implying the supply is good for the newer 24 pin designs,
but also covers the older 20 pin ones.

The above ampere numbers are not the whole story, but basically
you check to make sure the above numbers are more than the current
supply. That is the ampere capacity at max, and the computer will
only use a fraction of those numbers normally.

The supply label also has wattage ratings for the combined output
of the 3.3V and 5V rails. What that means, is either the 3.3V or
the 5V can be heavily loaded, but both cannot support more than
185W of total output. For example, 3.3V*20A and 5V*24A would bring
you up to that limit. Even though the ampere numbers haven't hit the
peak current limits, their combined load is a thermal limit inside
the supply.

Similarly, the total supply limit of 353W, takes all the rails
and their loading into account. 353W would be good for a lot
of computers, as long as they don't have a really power hungry
AGP or PCI Express card in them, at the same time as one of
Intels old 130W monster P4 processors.

If you need help gauging the power needed, there are power
calculator web sites, where you enter the hardware config you've
got, and they estimate how many amps of output capacity you
need, or the total wattage. Many of them will overestimate the
needed power, which is why I'm not going to promote them unless
you ask. If you just believe what they say, you'll end up with
a more expensive unit than is necessary.

Not all supplies are created equal. If you go to your local
computer store, you may see products that promise "500W" for
$20, but in practice they cannot really sustain that power level
for very many months without popping. Reading the reviews of some
of the cheaper ones on Newegg, should show you that cheap supplies
are a false economy. The funniest was the review from one guy,
who had bought four of the same cheap model, sequentially.
Never realizing, that for the price of four cheap ones, he could
have had one good one that was still running, and would not
have endangered his computer four times when they popped.

HTH,
Paul
 
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