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Let's talk power supplies
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Thunndarr



Joined: 30 Sep 2003

PostPosted: Thu Dec 14, 2006 4:38 pm    Post subject: Let's talk power supplies Reply with quote

So, I recently upgraded my power supply. Well, sort of. My old power supply was 450 watts, the new power supply is 450 watts, but it's got the 6-pin connector for my new video card. So far, so good.

But here's the deal. Before I picked up the new PSU, I looked at the power recommendations on the box of my video card, and it recommends a PSU of 450 watts (no problem there) with a 12V rail rated at 30 amps. Um, that's a problem.

Before I bought my new PSU, I checked trusty ol' Danawa for a decent PSU. I found a few 450 watt PSUs rated around 26-28 amps on the 12V rail. I wrote down the model numbers, headed to Yongsan, and was told by every single retailer there that they didn't carry ANY of the PSUs I was looking for. And these weren't exactly obscure brands, one was an LG, the other I don't remember.

I asked about the 450 watt PSUs they had, and the vast majority (all but the one I eventually bought) topped out around 18-19 amps. WTF? Oh, and I'm not exactly confident about the PSU I bought, but at that point I was in a hurry, and it was the only one that came remotely close to meeting my requirements (according to the manufacturer's claimed requirements, which I don't really trust since it was relatively cheap.)

So, how important is this whole 30 amp requirement anyway? If it is important, why don't more vendors carry decent power supplies? Most of the guys I talked to all carried the same crappy brand they put in the computers they have for sale, which we all know aren't exactly chock full of quality parts.
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Demophobe



Joined: 17 May 2004

PostPosted: Thu Dec 14, 2006 4:55 pm    Post subject: Reply with quote

You should look at the total combined wattage for the 12V and then divide it by 12. For example, if your PSU lists say a total combined W of 500 for the 12V your looking at total 12V A of 41.6+.

For you, looks like about 37.5 A. Shouldn't be a problem.
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Thunndarr



Joined: 30 Sep 2003

PostPosted: Thu Dec 14, 2006 4:56 pm    Post subject: Reply with quote

Demophobe wrote:
You should look at the total combined wattage for the 12V and then divide it by 12. For example, if your PSU lists say a total combined W of 500 for the 12V your looking at total 12V A of 41.6+.

For you, looks like about 37.5 A. Shouldn't be a problem.


So, you don't need to look at the listed amp number on the 12V line? Perhaps that's the part that's got me a bit confused.

Edit: This is what I'm looking at. (Not my power supply, just a convenient example.)

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eamo



Joined: 08 Mar 2003
Location: Shepherd's Bush, 1964.

PostPosted: Thu Dec 14, 2006 6:25 pm    Post subject: Reply with quote

I got an Acbel 450w from Yongsan about a year ago. It has been powering (24/7) my Dual Core 3.0ghz and 7900GT with no problems. Here's Danawa's pic of it's stats. 47,000



Of course, you could always just play safe and get a really powerful PSU (say, 750w) and then be assured it will handle anything you ask of it with ease. Some tech websites are totally positive that we will need PSU's rated at around 1000w to safely handle the new CPU's and GPU's coming out in the next couple of years.
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Wrench



Joined: 07 Apr 2005

PostPosted: Thu Dec 14, 2006 6:49 pm    Post subject: Reply with quote

Man I hate people thatt buy cheap shit PSU. I have always bought Enermax and I never had a single prob EVER. I still run an old Enermax PSU back home it must be at least 7 years old.


God I remember my dualy at home that thing had nothing but problems.. I was Using Sparkle Workstation PSU rated at 650W and my machine had nothing but problems got a 560w Enermax problems went away. The price difference was about 50$

Buy a good PSU with a GOOD solid 12 V rail.


I use to work supporting machines in dirty enviornments and good 50% of the calls were related to PSU failures because of Poor quality and Cheap parts.

Plus my PSU is completly SILENT.


Most PSU don't need much on the 5 volt rail any more because that was the day of the OLD Athlon/p3 Systems most Mobos NEED 12 Volt rails and so do cards.


Last edited by Wrench on Thu Dec 14, 2006 7:03 pm; edited 2 times in total
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Demophobe



Joined: 17 May 2004

PostPosted: Thu Dec 14, 2006 6:54 pm    Post subject: Reply with quote

Thunndarr wrote:
Demophobe wrote:
You should look at the total combined wattage for the 12V and then divide it by 12. For example, if your PSU lists say a total combined W of 500 for the 12V your looking at total 12V A of 41.6+.

For you, looks like about 37.5 A. Shouldn't be a problem.


So, you don't need to look at the listed amp number on the 12V line? Perhaps that's the part that's got me a bit confused.

Edit: This is what I'm looking at. (Not my power supply, just a convenient example.)




This is exactly what I mean. The orange 12v line puts out 30A. Now, this isn't a 'true' 450w. PSU, which is why it's cheap. That's kind of the second part of your post; why are the PSUs so cheap? That's why. They aren't really putting out the power they say. A true 450 would put out more than 30 A, as the math shows.

For eamo's picture, it lists "per 12v. line", but the total output can be the combined number. If the second rail is only putting out say 6 A, the rest can go through the first rail.
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eamo



Joined: 08 Mar 2003
Location: Shepherd's Bush, 1964.

PostPosted: Thu Dec 14, 2006 7:03 pm    Post subject: Reply with quote

Quote:
A true 450 would put out more than 30 A, as the math shows


So you are saying that when buying a PSU we should look at the two 12v figures, add them together, then hope you get something around 40amps or more?
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Wrench



Joined: 07 Apr 2005

PostPosted: Thu Dec 14, 2006 7:13 pm    Post subject: Reply with quote

Also I would like to add that the FAN inside your PSU does matter.

Silly but true indication of quality is the weight of the PSU. I kid you not heavier PSU tend to have better caps/resistors as well as Heatsinks.

Also more expensive PSU's will tend to have Ball Bearing fans and cheap ones will come with Sleeve bearings which tend to die rather fast.
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Thunndarr



Joined: 30 Sep 2003

PostPosted: Thu Dec 14, 2006 7:18 pm    Post subject: Reply with quote

Demophobe wrote:
Thunndarr wrote:
Demophobe wrote:
You should look at the total combined wattage for the 12V and then divide it by 12. For example, if your PSU lists say a total combined W of 500 for the 12V your looking at total 12V A of 41.6+.

For you, looks like about 37.5 A. Shouldn't be a problem.


So, you don't need to look at the listed amp number on the 12V line? Perhaps that's the part that's got me a bit confused.

Edit: This is what I'm looking at. (Not my power supply, just a convenient example.)




This is exactly what I mean. The orange 12v line puts out 30A. Now, this isn't a 'true' 450w. PSU, which is why it's cheap. That's kind of the second part of your post; why are the PSUs so cheap? That's why. They aren't really putting out the power they say. A true 450 would put out more than 30 A, as the math shows.

For eamo's picture, it lists "per 12v. line", but the total output can be the combined number. If the second rail is only putting out say 6 A, the rest can go through the first rail.


Actually, most of the PSUs I looked at in Yongsan had 12V rails around 17-18 amps. My real question was where to find a good one since all the vendors carry are cheap ones (at least, on the day I went hunting.)

Edit: I'm not really asking why they are cheap. I KNOW most of them are cheap. I'm asking where the power supplies with high amperage 12V lines are.


Last edited by Thunndarr on Thu Dec 14, 2006 7:22 pm; edited 1 time in total
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Wrench



Joined: 07 Apr 2005

PostPosted: Thu Dec 14, 2006 7:21 pm    Post subject: Reply with quote

Really good brands you should look for or ask is Tagan or Enermax.
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eamo



Joined: 08 Mar 2003
Location: Shepherd's Bush, 1964.

PostPosted: Thu Dec 14, 2006 7:37 pm    Post subject: Reply with quote

Scroll through the PSU's listed on Danawa and see what can be got. I've just been looking myself and there seems to be many, many, mid and high spec PSU's. Not everything listed on Danawa is actually available but most of it is.
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Thunndarr



Joined: 30 Sep 2003

PostPosted: Thu Dec 14, 2006 7:52 pm    Post subject: Reply with quote

eamo wrote:
Scroll through the PSU's listed on Danawa and see what can be got. I've just been looking myself and there seems to be many, many, mid and high spec PSU's. Not everything listed on Danawa is actually available but most of it is.


Well, I just have to say, on the day when I went looking, my only requirement was 450 watts and at least 30 amps, and nobody, I mean absolutely nobody, could hook me up with one.
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eamo



Joined: 08 Mar 2003
Location: Shepherd's Bush, 1964.

PostPosted: Thu Dec 14, 2006 8:13 pm    Post subject: Reply with quote

Thunndarr wrote:
eamo wrote:
Scroll through the PSU's listed on Danawa and see what can be got. I've just been looking myself and there seems to be many, many, mid and high spec PSU's. Not everything listed on Danawa is actually available but most of it is.


Well, I just have to say, on the day when I went looking, my only requirement was 450 watts and at least 30 amps, and nobody, I mean absolutely nobody, could hook me up with one.


Everything I've bought from Yongsan I've (well, my wife actually does it Embarassed ) ordered online. I've never had an out-of-stock problem and everything arrives by Taek-bae nice and quick. Sometimes just 18 hours after the order is placed. Try ordering online.
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Demophobe



Joined: 17 May 2004

PostPosted: Thu Dec 14, 2006 8:27 pm    Post subject: Reply with quote

As with many things in Korea, power supply specs are not really standardized, as I think very few people actually look. The standard method is to list the combined 12v rail amps or perhaps separately. I suspect that any PSU listed with 13A on the 12v. rail is incorrectly labeled, either in terms of overall wattage or what is potentially going through the 12v rail.

Anyhow, I provided the math for a standard PSU, and that is generally the rule. I personally have 2 350w PSUs, one outside the box running fans and my graphics card. Yes, that's how much I trust Korean PSUs. I wasn't going to drop the small fortune they wanted for the 500w I was after at the time, though prices for PSUs have come down in the last year or so.

I too order online, as going to Yongsan just isn't worth the time it takes to get things done, and the delivery charge is miniscule and the service is fast. I always call the same guy at Yongsan, and he gets exactly what I want everytime. Seems that when one goes there, the desired products become rare.
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Thunndarr



Joined: 30 Sep 2003

PostPosted: Thu Dec 14, 2006 9:21 pm    Post subject: Reply with quote

eamo wrote:
Thunndarr wrote:
eamo wrote:
Scroll through the PSU's listed on Danawa and see what can be got. I've just been looking myself and there seems to be many, many, mid and high spec PSU's. Not everything listed on Danawa is actually available but most of it is.


Well, I just have to say, on the day when I went looking, my only requirement was 450 watts and at least 30 amps, and nobody, I mean absolutely nobody, could hook me up with one.


Everything I've bought from Yongsan I've (well, my wife actually does it Embarassed ) ordered online. I've never had an out-of-stock problem and everything arrives by Taek-bae nice and quick. Sometimes just 18 hours after the order is placed. Try ordering online.


Well, I like ordering online also, but therein lies a rather large problem. How is one to keep the aforementioned video card + power supply purchase (which is no meager sum) hidden from the wife when she does the ordering?
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