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Won't Post w/ 12v plugged in

Last response: in Systems
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August 19, 2010 5:41:46 PM

Hey guys I'm doing my first build since the Pentium 4 3.0ghz was too expensive to even fathom and well, things have changed. I jumped in head first like with most things but this time, I'm having a problem.

I bought a Power Supply that does not have an 8-pin 4x2 12v, but rather the traditional 4-pin so, upon realizing this I went and bought a molex to 8-pin adapter and plugged it in and yet, still the same problem.

The problem is: With the 12v plugged in from the power supply the computer will turn on for 1 second then shut down, and will not do this again unless I cycle the power. With the 12v unplugged the computer will run and run and run but nothing happens because the CPU isn't getting power.

The dirty details:

Gigabyte GA-x58a-ud3r

600 watt power supply

Intel i7-930

More about : post 12v plugged

a c 104 ) Power supply
August 19, 2010 5:52:41 PM

Do you have another (known good) psu to swap out with?
Have you tried using just the 4pin block?
My Mobo has an 8pin socket, but I only use a 4pin,
I'm not sure about the adaptor you mention and you dont say what brand/model the psu is,
It may be that theres another issue,not yet apparent so lets get the psu out of the way and see how we go from there
Moto
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August 19, 2010 5:57:55 PM

I did try to initially use just the 4-pin with the same symptoms, but I read for the quadcore processor I need the 8-pin. The power supply is a Zalman zm-600hp.

The power cables for the GTX-460 are plugged in as well. The only thing that changes is if I unplug the 12v everything "works" -- If I plug it in nothing works. But obviously nothing works with the 12v unplugged either, it just appears that everything works. If that even makes sense. Like the fans are going and everything's running if it's not plugged in, but if it is it's a flash of power and that's it.
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August 19, 2010 6:00:16 PM

Also the only other PSU I have is a 200 watt so I'm afraid that won't even turn on my fans =P
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August 19, 2010 6:19:29 PM

I tried unplugging the graphics card and just running with the 12v and the same thing happened. Basically 12v plugged in = nothing. 12v not plugged in = computer starts and everything appears to be working, but without a CPU who knows. But it'll stay running for awhile...
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August 19, 2010 6:32:01 PM

With two 4-pin connectors plugged into the 12v I get a quick red LED which, according to my manual, is indicating that the SB voltage is high. Any of this helping?
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a c 104 ) Power supply
August 19, 2010 7:52:41 PM

Fast answer sry, off to work in a minute,
If you can use a multimeter, check your 12v cpu line is actually working ok, if not, try a lock pc shop, just take the psu down and ask politely if they'll check it for you :) 
might be rma time though
Moto
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August 19, 2010 7:56:32 PM

Np, thanks for your help. Thinking RMA for the PSU or for the MB? I've read 3 other people having identicle issues, some claim MB some claim CPU, nobody posts their solutions!
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August 19, 2010 7:57:30 PM

Thanks Proximon, I've been over those all and have tried every thing, only one things remains constant. 12v power in - quick on quick off. 12v power out - on and running but no functionality whatsoever.
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a b ) Power supply
August 19, 2010 8:07:02 PM

That kinda sounds like the PSU is getting tripped. Short under the board or a bad case switch?

Did you actually breadboard?
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August 19, 2010 8:12:47 PM

No actually, I guess it's the only thing from the sticky I didn't do... it's my next step I guess, exhausting all other options. I just can't see how it's a short when everything runs fine without the 12v plugged in so I really didn't think that it would help.
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a c 104 ) Power supply
August 20, 2010 6:45:40 AM

I meant for you to rma the psu initially,
once you have a replacement psu, if your still having issues it points more to the Mobo, but with lack of psu testing I'd edge for the psu causing the problem.
Moto
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a b ) Power supply
August 20, 2010 7:39:35 AM

You need to understand that ALL boards do that, seem to power up without the 4/8 pin.

Something is getting tripped very quickly when the CPU is given power. Could be the board, could be the CPU, could be the PSU. It's simple to rule out a case switch short or short on the underside of the board, and then you have to switch parts after that to narrow it down further.
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August 20, 2010 8:17:16 PM

Working on it now guys, I was fairly defeated yesterday so I just walked away from it, feeling much better today and ready to tackle everything head on. I'll keep you all posted, thanks for the help I know I'm at least headed in the right direction. Will buy a new power supply today if it's not a short or the CPU seating - can always return one of them.
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a b ) Power supply
August 20, 2010 8:32:22 PM

Normally the MOLEX to 8-pin adapters are for video cards and not the CPU connector so make sure you have the proper adapter (4-pin MOBO to 8-pin MOBO connector) if using an adapter trying to use aan 8-pin PCI-e adapter in the MOBO plug could be a problem since the wiriing is different !!
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August 20, 2010 9:00:59 PM

I actually had 2 4-pin adapters so the PSU has a wider range of compatibility, I really just didn't realize it. I've got it out of the case on cardboard and it's still not starting, going to use an old pentium II CPU fan to plug in (since it's watercooled at the moment) to see if maybe that'll get it to turn on, since what I had in there was a 3-pin fan, maybe being a 4-pin will make a difference? I don't know. After that I'll try to reseat the CPU and see if that works. There's no metal from the CPU Waterblock touching the motherboard on the back, either. After I try the fan, reseating the CPU, and using a different PSU -- I'm all out of options and guess I'll just have to RMA the board.
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a b ) Power supply
August 20, 2010 9:05:07 PM

Yep nothing else to do.
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August 20, 2010 10:12:04 PM

Alright so here's something new. I was going to reseat the CPU but something just tried my curiosity I guess as all I did was loosen the waterblock a little bit from the back of the motherboard and I felt like giving it a shot (the metal bracket is not making contact with the back of the board, rather there is a black pad inbetween the two) Just loosening it now causes the computer to power cycle. On for 4-5 seconds (much longer than before) then off for 5 seconds or so. Then back on. Again, and again. Eagerly awaiting responses =P
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August 20, 2010 10:32:56 PM

How about getting it working on the stock aircoolers before you complicate things with your watercooling blocks?
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August 20, 2010 10:43:11 PM

Didn't buy a stock aircooler, doubt my Pentium II fan will be compatible.
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August 20, 2010 10:58:50 PM

Got it from superbiiz. Just came with the CPU in a small plastic casing with a rubber band around it.
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a b ) Power supply
August 21, 2010 12:28:20 AM

Sometimes you can get stress on a socket that causes issues. I have also heard of retention brackets that were not compatible with certain boards and could damage them.

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August 21, 2010 1:08:33 AM

dndhatcher said:
You didnt get it in a blue box with a stock aircooler already included? I didnt know intel sold them any other way.
http://www.newegg.com/Product/Product.aspx?Item=N82E168...


It's actually quite common... either he bought an unboxed ex-display model or an OEM model... the CPU is the same.. the difference being price and a lack of packaging / stock cooler
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