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Question about PSU's & motherboards/grounding

Last response: in Components
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November 26, 2011 6:39:06 PM

If a motherboard is not grounded correctly, will some power supply's refuse to turn on?

I have a cheap 30$ cooler master 460w that has always worked, however none others will... I have tried a bunch of reliable brands that refuse to boot the computer when hooked up correctly, and when shorting the 2 pins in they all worked.

I gave up but a few weeks ago my computer shut off and didn't go past the BIOS screen, and I took it apart and it turned out my mountain pins were incorrectly placed. Some screws were missing & were different sizes.

Do more expensive power supply's have some sort of anti-boot because it could detect it or something? Could this possibly have been the reason?
a b ) Power supply
a b V Motherboard
November 26, 2011 8:37:35 PM

mountain pins? never heard of them XD you mean mounting pins?
have you checked over the buttons on the faceplate (the connections to the mobo) it couldve been somthing like the power button was plugged into the wrong place
and if your case is metalic (and conductive) you MAY have shorted the board...usually the PSU has a grounding cord of sorts
have do you have a mouse keyboard and hardrive plugged in?
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November 27, 2011 1:11:52 AM

nna2 said:
mountain pins? never heard of them XD you mean mounting pins?
have you checked over the buttons on the faceplate (the connections to the mobo) it couldve been somthing like the power button was plugged into the wrong place
and if your case is metalic (and conductive) you MAY have shorted the board...usually the PSU has a grounding cord of sorts
have do you have a mouse keyboard and hardrive plugged in?


yeah, lol

Nothing I can check now, my computer is working, but it didnt with the more expensive power supplys... now all my mounting pins are correctly their but they used to be all screwed up like I said, im wondering if some power supply's will not turn on if it can tell if its not on their right...
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a c 162 ) Power supply
a c 493 V Motherboard
November 27, 2011 2:23:57 AM

Juicy555 said:
If a motherboard is not grounded correctly, will some power supply's refuse to turn on?

I have a cheap 30$ cooler master 460w that has always worked, however none others will... I have tried a bunch of reliable brands that refuse to boot the computer when hooked up correctly, and when shorting the 2 pins in they all worked.

I gave up but a few weeks ago my computer shut off and didn't go past the BIOS screen, and I took it apart and it turned out my mountain pins were incorrectly placed. Some screws were missing & were different sizes.

Do more expensive power supply's have some sort of anti-boot because it could detect it or something? Could this possibly have been the reason?

If you are asking if an extra standoff under the motherboard could have grounded out a solder trace on the back of the board, yes.
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a b ) Power supply
a b V Motherboard
November 27, 2011 2:35:06 AM

If a lesser PSU works the better one should work too.

What are the makers, models, approximate usage statistics, and approximate age of all the PSUs in question?
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December 4, 2011 9:21:24 PM

Raiddinn said:
If a lesser PSU works the better one should work too.

What are the makers, models, approximate usage statistics, and approximate age of all the PSUs in question?


my current working one is a 460w cooler master, http://www.coolermaster.com/product.php?product_id=3686

and these are the ones i have tried

http://www.amazon.com/gp/product/B001EYV690/ref=oh_o04_...
http://www.amazon.com/gp/product/B004W2T2UQ/ref=oh_o03_...
http://www.amazon.com/gp/product/B001Q3LWL6/ref=oh_o00_...

All had the same problem, would not turn on the computer. Jumping the cord turned it on, and worked in a different computer.


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a c 162 ) Power supply
a c 493 V Motherboard
December 5, 2011 12:08:17 AM

Did you check to see if there was an unused standoff behind the board that could be shorting it out? Do you have a VOM meter available, and do you know how to use one?
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a b ) Power supply
a b V Motherboard
December 5, 2011 12:41:23 AM

If the more expensive PSUs have multi-rail designs and you loaded everything on one rail then they wouldn't boot.

Also, correct me if I am wrong here but it sounded like you said that all of the PSUs will work as long as you short the appropriate wires. If that is the case, it sounds like the power button is bad or you don't have the wiring installed correctly.
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December 5, 2011 4:26:51 AM

Raiddinn said:
If the more expensive PSUs have multi-rail designs and you loaded everything on one rail then they wouldn't boot.

Also, correct me if I am wrong here but it sounded like you said that all of the PSUs will work as long as you short the appropriate wires. If that is the case, it sounds like the power button is bad or you don't have the wiring installed correctly.


How could I know if it was all loaded on 1 rail or not?

I checked and they were all installed just like the working one, the power button is working , it works with the 460w one. I have also tried shorting 2 pins to start it with a screw driver in the mobo with no sucess.
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a b ) Power supply
a b V Motherboard
December 5, 2011 4:15:30 PM

The most straightforward way to determine these things (if you can trust the manufacturer not to lie) is to look at the PSU label.

Here is a webpage that shows the label for the Cooler Master 460.

I will just assume for the sake of argument that the Cooler Master manufacturer doesn't lie on its labels.

http://www.coolermaster.com/product.php?product_id=3686

If you look at the RS-460-PCAR-A3 label, it shows

3.3v = 22a
5v = 25a

That means the most you can draw off of the 3.3v at once is 3.3v x 22 = 72.6w
On the 5v you can get 5 x 25 = 125w

If you add both of those together you get just about 200w in total (197.6w). However, under those you see a box that covers both spaces that says 165w on it. This means that both of these are "tied" together, so to speak, and the max you can get from both of them in total is 165. However you connect items to these power things it can't use more than 165 out of the theoretical 197.6w maximum.

Moving over to the 12v lines, the most important type for computers in 2011 you see that there are 2 listings and both say 18a. Each of them can theoretically do 18 x 12 = 216w. Totalled together that would be 432w. However, you see a box right below them that shows them linked together with a maximum usage of 312W. That means that 120w of the theoretical potential of the wires can never be realized.

If you go above the combined figures from the bottom row with the total of the draw from the individual lines, then the PSU will, you hope, just shut itself down to protect the computer. It is also possible, especially for cheapy PSUs, that a part literally melts and a boatload of current flows through the wire to whatever is on the other side and melts that too (like a video card).

There are a whole slew of protective features that have been invented to help protect parts from being damaged by power. Most of them aren't used by cheapy PSU makers, leaving all the risk in the hands of the PSU users.

Going back to the power thing from before....

To some extent it is going to be trial and error to find out if you are overloading some wires.

If you are trying to get more than 312 in total out of the 12vs, you are overloading it. That part is pretty easy.

The thing about it, though, is that each of those 18as on the 12vs can be overloaded individually. There are two "halves" to the power delivery and each one can only do a max of 216.

A high end processor is about 125w. Even low end or mid range ones are 65 or 95w. All of that figure goes on one rail. Then you have a video card that may pull another 200 itself. If it uses the motherboard slot (75w) and 2 x 6 pin PCIE connectors (2 x 75w) that is 225w.

As you can see, the 225w can't fit on 12v x 18a (216). The only way to get a card like this to work would be to have the motherboard slot pulling from one rail of 18 while the two PCIEs pull from the other rail of 18.

That would leave 75 on one side and 150w on the other side, both of which are under 216 so theoretically OK.

That being said, a 125w processor and a 225w video card would be 350 in total and it would blow right through the 312 max output for the 12vs x 2 so any time this theoretical system drew max power it would either shut down or start melting parts.

It is also possible that the manufacturer lied and wrote 18a when they really meant 15a and they wrote 312 w total when they really meant 250w total. You would never know this and you could dutifully hook up things thinking the label was accurate and potentially destroy your parts as a result.

These considerations are why people here always advise to stick with certain brands (known not to lie, or to even label power conservatively) and why single rail designs are easier to configure than multi-rail designs.

If the 165w and 312w (separate rails, overloadable individually) were just one bar that said 477w on it (single rail), then you could take more juice out of the 12vs and less out of the 3.3s and have a PSU that still works just fine.

In a practical sense, you can only really play around with the power connections and try to re-engineer the setup and then try to turn it on again and see if it works the next time.

So you could just start taking power cords out of the back of, say, your hard drive and then replace them with power cables on a different wire and try to turn it on.

If you are having load balancing problems, that could fix it.
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a c 243 ) Power supply
a b V Motherboard
December 5, 2011 7:24:29 PM

Juicy555 said:
How could I know if it was all loaded on 1 rail or not?

I checked and they were all installed just like the working one, the power button is working , it works with the 460w one. I have also tried shorting 2 pins to start it with a screw driver in the mobo with no sucess.

Your not, rail balancing isn't the problem, if it was the Coolermaster 460 with it's dual 18 amp rails wouldn't work either.
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December 12, 2011 4:00:22 AM

delluser1 said:
Your not, rail balancing isn't the problem, if it was the Coolermaster 460 with it's dual 18 amp rails wouldn't work either.



well im dun goofed
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a b ) Power supply
a b V Motherboard
December 12, 2011 4:53:48 PM

Unless the good ones are DOA, which they aren't afaik because it sounded like you said the good ones work if you short the pins, then there is no good reason that the good ones should fail and not the bad one unless they all have a specific protection that the bad one does not have.

Even then, the bad one would have to be operating when it shouldn't be.

If any of that is not true, then the problem would most likely fall to some sort of difference that can only happen with the good ones like a problem with wiring or something.

If you are sure you are wiring the new ones up just like the old one, then look at the 3 new kinds and see what protections they all have in common that the CM 460 doesn't have.
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