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Old 04-14-2008, 05:25 PM   #1
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Is there a way to tell my power supply wattage

Is there a way of finding out my power supply wattage without taking the cover off my box?
Old 04-14-2008, 08:35 PM   #2
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No, the PSU doesn't report anything to the software running on the machine. It is just a dumb power transformer (though I imagine this is likely to change in the near future, with efficiency becoming such a hot topic).
Old 04-14-2008, 09:22 PM   #3
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Actually the future is here... Computer PSUs are fairly complex switching power supplies and on average most are on the order of 70-75% efficiency but there are some that are 80-85% or more. Basically switching power supplies have smaller transformers which means they weigh less and can handle a wider input voltage/frequency range then the equivalent linear power supply.

If by a small chance the voltage/current ratings are printed on the case near the power cord then we can calculate the wattage but as already posted nope.
Old 04-14-2008, 09:54 PM   #4
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Sadly, the answer is almost certainly no. With the number of international regulatory bodies that require various things on that label, the label is too big to fit in the space left on the back panel of the power supply box. But if you can take the main cover off, you might be able to read the label (using a mirror, maybe) without actually removing the power supply module from the main chassis. The label will be on one of the large sides of that box where the power cord plugs in.
Old 04-14-2008, 10:36 PM   #5
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If the PSU was installed properly then the specification label will be visible once you take the side cover off. You could get lucky and the manufacture,model number for the PSU is sometimes labeled on the outside panel plate just under the AC plug.

Another way would be to get the model number for the system then search on the manufacture site.
Old 04-15-2008, 02:56 AM   #6
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OK, thanks for that guys, I guess it's out with the screwdriver then.
Old 04-17-2008, 05:44 AM   #7
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April 17, 2008

Hi Mikieboy

Just a word of caution.

A PSU label may clearly state the total output wattage of the unit.
However, there are power limits on the different voltage supply lines.

For example.

A PSU's total power output may be clearly rated.
However, there may be a maximum power limitation on the combined supply
of different sets of voltages. Commonly +5V and +12V.


a hypothetical ATX PSU might be labeled as 235W
but on closer inspection you cannot draw more than 145W from both the +5V and -5V voltage lines combined (ie at the same time).


Power = Voltage x Current

You need to examine the PSU closely to see what the maximum current levels
are for each of the voltage lines, and operate below these levels current levels.

In addition, beware of drawing currents near the maximum ratings for the power supply voltage lines, since these voltages (although regulated) may vary for very very short periods of time on system startup. (ie. instabilities under maximum load).

As a rule the wattage of a PC power supply cannot be determined without a visual inspection. However, there are very expensive Pentium 4 power supplies that come equipped with integrated monitoring hardware. This hardware is linked by a USB cable to a USB port on the motherboard, and the health of the power supply is monitored by application software running on the PC.

Hope that helps.

Old 04-17-2008, 09:05 AM   #8
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And beware of the fact that if you exceed the maximum for even a split second you have a good change that you blow up the hole
power supply ,the same happens when it get short circuit fore a little while.
The good thing is that you do not use every think at the same time
AS a example instance if you let say 4 HD in the box you do not all the four at the same time

all the best


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