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Calculating PSU question.

K

Kwipper

n00b
Joined
Aug 18, 2006
Messages
34
I am having a hard time trying to figure out power supplies. I thought that combining the +12v rails (On PSU's that had multiple ones) would give the amperage rating you need to know on video cards. I was wrong.

I was told that instead you need to find the number showing the max. wattage between the +12v rails and divide that by 12 to get the amperage rating.

However, lets say you're browsing power supplies in a retail store and you come across... this...

http://c1.neweggimages.com/NeweggImage/productimage/17-153-040-05.jpg

It doesn't show the combined wattage of the +12v rails anywhere, so how are you supposed to calculate this? What's the formula?
 
AFAIK, there's no formula for those cases where there is no info whatsoever about the total amperage on the +12V rail.

If the total combined or max wattage can't be found on the power supply, check the manufacturer's site page for that PSU for that info. If the manufacturer doesn't provide that information, it's generally a good sign for you to drop that power supply from consideration.

In this case, on Thermaltake's own website, it shows that there is 52A on the +12V rail for that Toughpower 650W:
http://www.thermaltakeusa.com/Category.aspx?C=1264

See the +12V column?
 
in DC: Power = Voltage * Amperage, but there's no formula for information that's not given. Fundamentally each 12V rail pulls from the same bridge rectifier, and that bridge rectifier, according to thermaltake, will output a maximum of 52A half-cycle average. But they shouldn't expect you to know that.

And yeah, aeons ago the Tough Powers were considered excellent buys but these days, with the likes of BFG and Corsair in the battle, Generally speaking its best to go with them instead.

And if you post the exact specs for your system these boards will give you recommendations a whole lot better than any PSU calculator.
 
actually The bridge rectifier is probably capable of much less than 52A, but that is in the primary where the power is still 230V/120V...the secondary rectifiers are where the 12V spec would be obtained...although I bet they are good for more than 52A.
 
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Do you have any reference that confirms a 120V rectifier in a PC power supply?
 
Ahh yes. Of course it would mention it on the website, but if I was in a retail store with no access to the website, I would probably never be able to get this kind of information.
 
Kwipper said:
Ahh yes. Of course it would mention it on the website, but if I was in a retail store with no access to the website, I would probably never be able to get this kind of information.
Click to expand...
Well, yeah. If you're in a retail store and the information isn't displayed, you don't really have a way of getting it save for getting on the internet somehow and doing some research. You should always research before making a hardware purchase anyway.
 
I'm in a similar situation at the moment. I have a Cooler Master 600w from an old setup that I want to use in a newer system. I'm gonna be using a 9600 GT that needs a rating of 26 amps on the 12v rail. I've looked all over Cooler Master's website and it looks like they went out of their way to tell me everything but what I needed to know. Hopefully when that card arrives it works out fine.
 
Certain said:
I'm in a similar situation at the moment. I have a Cooler Master 600w from an old setup that I want to use in a newer system. I'm gonna be using a 9600 GT that needs a rating of 26 amps on the 12v rail. I've looked all over Cooler Master's website and it looks like they went out of their way to tell me everything but what I needed to know. Hopefully when that card arrives it works out fine.
Click to expand...

Is it the Extreme Power series? If so, it might not work for long or well depending on your setup.
 
Danny Bui said:
Is it the Extreme Power series? If so, it might not work for long or well depending on your setup.
Click to expand...
Yeah. Its Extreme Power. Im gonna give it a go. I had it stable in another setup before and it was rock solid for a long time. This new setup that I'm going with and using for my HTPC is basically the same so I don't foresee having a problem. But, if in the end I have to get another PSU then so be it.
 
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