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Old 07-20-2009, 01:06 PM   #1
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Default Seventeam ST-620PAF Power Supply Review

There has been a new article posted.

Title: Seventeam ST-620PAF Power Supply Review
URL: http://www.hardwaresecrets.com/article/765

Here is a snippet:
"You need to pay close attention because Seventeam has two power supply series with practically the same name but using different projects: PAF and P-AF. PAF series has models with 450 W, 520 W, 580 W ..."

Comments on this article are welcome.

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Old 07-21-2009, 03:57 AM   #2
Olle P
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I've found a couple of... let's call it weaknesses... in this review:

First your comment on power distribution:
"... not a good distribution, because +12V2 will be overloaded, ...
... +12V1 rail will always work lightly loaded, as the motherboard and peripherals don’t pull a lot of current/power.
"
This is countered quite a bit by the offset in power rating on the two lines, 18A for 12V1 and 30A for 12V2. It will take some hefty graphics card and CPU to use that much, given that they also draw power from the motherboard.
At the same time a rig with only four HDDs and the motherboard hooked up to the 12V1 line will draw more than 18A during startup.

Next we have the power tests.
Here I think your choice of 12V load distribution is way off, given the comments above. Even though you clearly state that 12V2 will normally take the brunt of the load, you overload 12V1 in tests 4 and 5, while leaving 12V2 comfortably not only below rated maximum but also below 12V1!
Instead you should definitely pull about 50% more from 12V2 than from 12V1.

The overload test, same issue:
You pull only 10% above rated maximum for 12V2 and try to draw a conclusion, instead of testing 12V1 where your equipment can pull 83% above rated maximum.

Finally we have the analysis of the secondary stage:
Your check of the components used end up at a theoretical maximum +12V output of (only) 43A, whereas the PSU is rated for up to 48A and your overload test show it can actually provide 52A, which is 21% above the theoretical maximum!

Comments are welcome!

Cheers
Olle

Last edited by Olle P; 07-21-2009 at 04:00 AM.
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Old 07-21-2009, 09:34 AM   #3
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I wish the efficiency were better, but it's still a "cheap" PSU here, cheapest than the Corsair 550/520 here.
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Old 07-22-2009, 03:41 PM   #4
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OlleP,

I prefer to use the same pattern for all power supplies we review, this way we have comparable results. The pattern used here was the same one used on Enermax ECO80+ 620 W. If we use different patterns we cannot compare the results directly.

I also want to add that you like to discuss a lot about rails and distribution, but I want to clarify that all +12 V rails are "virtual". Inside the PSU they are all connected together to the same point. The difference between rails is where the OCP circuit is connected. The numbers on the label usually mean nothing. In theory they should tell us when the OCP would kick in, however manufacturers always set the trigger point way above what is written on the label, making these numbers useless. I suggest you to read this part for a more detailed explanation:

http://www.hardwaresecrets.com/article/181/12

It will become clearer when I post the updated version of the "Anatomy of Swtching Power Supplies" tutorial, where I will show the electrical connections for this.

Cheers,
Gabriel.
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Old 07-27-2009, 10:41 PM   #5
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Gabriel, I think you're contradicting yourself!

First you claim:
Quote:
Originally Posted by Gabriel Torres View Post
I prefer to use the same pattern for all power supplies we review, this way we have comparable results. The pattern used here was the same one used on Enermax ECO80+ 620 W. If we use different patterns we cannot compare the results directly.
And then go on to state:
Quote:
Originally Posted by Gabriel Torres View Post
... all +12 V rails are "virtual". ..., making these numbers useless.
To me that last part reads that you most definitely should get the same result with a different load pattern within the 12V rails, as long as the total 12V load is the same!

Quote:
Originally Posted by Gabriel Torres View Post
I also want to add that you like to discuss a lot about rails and distribution, ...
Only because you do, in the reviews.
There you comment that the distribution is good/bad/okay. If it's all virtual and the numbers useless, then the only conclusion must be that any distribution is fine!

My points on this specific review is that the nominal limits on the two 12V rails are quite different, and the tests should reflect that!
In test 5 you stress 12V1 by 44.4% above that nominal limit while you could just as easily, by increasing the 12V2 load, apply the same total 12V load without pulling more than 18A from 12V1.
Then you try to draw some useless conclusion from a 10% overcurrent on 12V2, where the OCP isn't expected to kick in anyway. Why not get the most out of your equipment and see if/when the OCP on 12V1 will kick in below 83% overcurrent instead?

Cheers
Olle
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