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Please help, newly built computer won't power up

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January 6, 2010 1:12:25 PM

Hello there, I should preface by saying that this is my first time building a computer. I assume I've install the necessary parts for a computer but when I tried turning it on, it powers up for a second or two and then the power cuts off. I have tried plugging in peripherals such as a keyboard and mouse; and the green light on the keyboard lights up so I'm not too sure what or where the problem is. I don't get any beeping from the motherboard either, as the computer just powers up with all the fans, led lights inside the chasis and motherboard running and then the powers cuts out.

Specifications for the computer include:

Gigabyte GA-P55A-UD3 Motherboard,
Intel i5 750 CPU
Powercolor Radeon 5770
Kingston 1800 DD3 2x2GB RAM
IDE Hard Drive
IDE Optical Drive
Corsair 750W PSU

Any help would be very much appreciated, thanks
a b V Motherboard
January 6, 2010 1:16:56 PM

Did you follow the steps in the "Read Before Posting about Boot Problems" sticky? If not, do that. If so, what happens for the different steps?

Does a light on the motherboard come on? What exactly do you see happening? Are all the cables plugged in?
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January 6, 2010 1:55:52 PM

Wow, thanks for the quick reply. I found out about that sticky right after I posted this tread. I think my may be an issue of short circuiting but I'm not too sure actually where as I made sure the standoffs were installed correctly and that there are no wires running behind or over the motherboard. In terms of the lights, there are 4 led lights on the upper right hand corner which vary from different colours and turn on, but they shut off with everything else after a second or two. I believe all the necessary cables are plugged in. Unfortunately I have a Antec 900 so I don't have a internal speaker at the moment. Also, another tricky thing about this Gigabyte motherboard is that there's a power fan, system fan 1 and system 2 internal connector. Because there's 2 4-pin peripheral power cable with four connectors, I ended up connecting 4 fans to 1 4-pin peripheral power cable and then to the power fan connector on the motherboard and then 1 4-pin power cable to the 2 IDE drives and then to a system fan 1. I've tried every possible combination as well.

That was a lot, but thanks again for your reply and help
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January 6, 2010 3:49:57 PM

That gigabyte board has IDE connectors or are you using an adapter of some kind? Are these salvaged IDE drives from a previous computer?
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a b V Motherboard
January 6, 2010 4:41:06 PM

Ok lets um try to interpret what you said.

"Because there's 2 4-pin peripheral power cable with four connectors, I ended up connecting 4 fans to 1 4-pin peripheral power cable"

Ok, this is a molex conenctor, when you say 4 pin peripheral cable do you mean this?


If so then ok that's fine. Connecting them on top of each other is called daisy chaining.

"and then to the power fan connector on the motherboard"

ok there's only 1 4 pin power on the MOBO and that's for the CPU fan.
Its the slot labeled CPU fan in this pic


(couldn't find a schematic pic for the UD3, but it's labeled the same)

and looks like


So please tell us what you actually did, because you can't actually connect the molex connectors to a mobo 4 pin connector.

"1 4-pin power cable to the 2 IDE drives and then to a system fan 1"

I assume you're talking about a molex again here and you connected them to your IDE drives and then a fan molex.


Make sure the 20pin is connected to the motherboard.

most ppl don't screw up here. They sometimes forget to plug in the ATX 12V

which goes in the top left of the schematic, where it says atx 12V.

Unless your PSU has some serious issues you should at least be posting if those 2 power cables are connected (and gpu and monitor obviously).

The 5770 must be properly seated into the slot and requires a 6 pin connector here

which looks like
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January 6, 2010 7:50:45 PM

Hi there, and thanks for the reply. So in a Antec 900 case, there's 4 fans which have molex connectors. I didn't stack them on top of each other, but instead connected the connectors one to one. As for the power fan, system 1 and system 2 fan, they don't show up entirely well in this image but you can kind of see the system 1 fan socket beside the the RAM sockets (underneath "dts"). The power fan socket is beside the ATX 24 pin socket on the left side and the system 2 fan is east of the power fan socket when looking at the picture.

http://giga-byte.ca/FileList/Image/mb_productimage_ga-p...

I realise that in this image that I was connecting the floppy cable into the fan sockets. Not good...

http://www.ixbt.com/short/images/tx_conn.jpg

But would it short circuit the entire motherboard or power entirely. I doubt it because as I mentioned, when I connect the keyboard the led lights up normally. I have unplug the floppy cable from the motherboard but still no luck. I've connect a PCI-E cable to the Radeon 5770 without any problems Anyhow, thanks for the reply and thanks thus far
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January 6, 2010 7:54:29 PM

mortonww said:
That gigabyte board has IDE connectors or are you using an adapter of some kind? Are these salvaged IDE drives from a previous computer?


Hello and thanks for the response. The board has one IDE socket where an IDE cable can be connected. So because these IDE drives are salvaged from a previous computer, I decided to connect them together with an IDE cable to the motherboard. I could try to connect a SATA hard drive to the motherboard but I think it has something to do with the power short-circuiting. Thanks again the reply
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a b V Motherboard
January 6, 2010 8:09:13 PM

Ok so, I think what you're saying is that you connected the Fan Molex cables to molex's (good) and then the CPU's Fan's long thin wire to the mobo 4 pin, and the long thin wire's from the fan's to the sys 1, 2 and power fan slots.



That's also fine, though the long thin cables are used to control fan speeds, not power them, and except for the CPU fans one, are optional.

Now like I said. Make sure your 20 pin and ATX12V 4 pin cables are connected to the MOBO. When you say PCI-E cable I assume you mean the 6-pin cable (I'm trying to make you use things actual names to avoid confusion).

If all that is properly connected and seated that's good, it, like all other cables should click and lock into the notches for them.

Now, if your computer is not POSTING (a mobo connected to a PSU, GPU and monitor will post, it'll give an error, but still post. Well technically you don't need the GPU and monitor, but it's kinda nice to see it posting).

Now if you did all that, then check the polarity on your front panel cables. Specifically, make sure the power button cable is has the correct polarities.


It's the cable labeled Power SW in this picture.

If its got its polarities reversed, the computer will do the exact error you've described.
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January 6, 2010 8:41:02 PM

I've tried POSTING with the monitor, keyboard, mouse, etc... all together and all alone but the computer still just shuts off. I believe I've connected the front panels correctly as well. Black and white are negatives while coloured wires are positive. Either way, I've tried all the combination possible but still, the computer still cuts out
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a b V Motherboard
January 6, 2010 9:42:25 PM

Um no....for a power switch connector there is 1 black 1 white wire, 1 of which is - and 1 of which is +.
There is no standard color for which is + which is -.

The reset switch for example doesn't care which end you plug into + and which into -.

Read the mobo manual and make what has to go where. If you have the Power SW white and black wire connected to - slots then the PC won't start for obvious reasons.
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January 6, 2010 11:24:41 PM

I think you should strip your machine down to bare essentials and try to boot up and get into the bios. Only connect CPU, 1 stick of ram, video card, power supply, keyboard and monitor. turn the pc on my shorting the 2 power pins with a screwdriver.

Also did the motherboard come with a small speaker? If so, plug it in to get some extra information.
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January 7, 2010 8:48:59 PM

Hello there and thanks for all the replies and suggestions. After performing a PSU test myself, I ended up bringing the computer to a service centre. And the conclusion from the diagnostic was that the motherboard has malfunctioned. So I'll be sending my motherboard to the US from Canada which is a bit of a drag. Oh well, it was good practise to assemble and disassemble the computer as well as read the comments and advice from everything. Thanks again
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