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Pc Boots For 3 Seconds Then Shuts Off

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#1 alphanumeric


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Posted 13 March 2007 - 08:52 PM

This is my first pc build. I've got everything in place and go to turn on the power and it comes on for about 3 seconds then powers off again. There are no beeps or anything. I have taken apart and put everything in multiple times with the same result. I finally was able to pinpoint it down to the power sw plug on the case itself. The system wont turn on without this plug in the motherboard, obviously, but when it is plugged in it will only stay on for about 3 seconds. If I turn on the power with the power sw plugged in and unplug it before it shuts off it will remain powered on. I thought maybe the motherboard was being shorted in the chassis itself so I took everything out and put it all on a rubber mat. I still get the same results. The system powers on for 3 seconds but will not stay on unless I pull the power sw plug off the motherboard. The only way to get it running is to turn it on and pull that plug (power sw) really quick and it stays on and it goes to bios where I can see everything else is fine. it recognizes RAM, processor, dvd drive, hard drive.

Once again this is my first build so I dont know exactly what I'm talking about but was hoping some of you more experienced users might be able to help me out. Heres some specs just in case it helps:

the case is thermaltake tsunami dream, motherboard: asus m2n-e. cpu: am2 athlon 64x2 4200. ram: 1 Gig kingston ddr2 667. I hope thats enough information. Thanks if anyone can give me any ideas on what to do!!

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#2 dc3


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Posted 13 March 2007 - 11:29 PM

Hi alphanumeric and welcome to BC.

The only thing that you didn't mention that I would be curious about is your PSU. Does it have the 24 pin connector and the square 4 pin connector for the CPU?

The PSU relies on the motherboard to turn on and stay on, there is one green wire in the bundle from the PSU that is the power supply on, the board will short this to ground to turn on your PSU. You can place a wire jumper between the green wire and any black wire to turn on the PSU when it is disconnected from the motherboard.

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#3 alphanumeric

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Posted 13 March 2007 - 11:46 PM

Whoops. I forgot to mention that. I have a rosewill 550W psu. It is a 20+4 pin connector as well as the 12v 4 pin power connector. I do see the green wire you mentioned. Unfortunately I have no clue about wire jumpers and how that works. I don't know what I've gotten myself into.

#4 gregmallek


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Posted 27 December 2008 - 10:40 AM

Hi! I am also having this problem, except that my computer won't keep booting up even if I DO pull the power switch cable. I have tested the PSU, changed the RAM for RAM that I know works from another system, re-seated all cables including SATA drive, DVD drive, and power cables, taken out all PCI interfaces, and removed all front panel connectors. I even took everything apart and re-seated the CPU, and all the pins and interface look intact. This is a new build (I have built 5 other computers over the years with no problems at all), mobo is Asus M2N-MX SE plus, cpu is AMD Athlon 64 x2 5000+, RAM is Corsair 1GB DDR 2 PC6400 stick (then tested with working 1GB Kingston PC5400 stick). The only thing i did differently with this build is that I got a CoolerMaster Gemini II heatsink and attached a 120mm fan to it, plugged into a constant 4-pin power cable, so there is nothing plugged into the mobo's "cpu fan" connector. Can this have something to do with it?

#5 garmanma


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Posted 27 December 2008 - 11:32 AM

With the switch wires disconnected, plug the computer in and short the 2 terminals on the motherboard that the switch plugged into, with a flat screwdriver blade. It should start.
I would also check the rest of the front panel connections to make sure they are correct

Put everything back together without the CPU and try it. If it turns on and continues to run it's the CPU


Caution: There are electronics inside the case that are very susceptible to electrostatic discharges. To protect your computer, touch the metal of the case to discharge yourself of any electrostatic charges your body may have stored before touching any of the components inside. As a safety precaution you should unplug the computer to avoid electrical shock.
The purpose of this procedure is to bypass the motherboard to test the PSU.

This procedure will involve working with live 12VDC electrical potentials which if handled improperly may lead to electrical shock. Proper precautions should also be taken to prevent electrostatic discharges (ESDs) within the case of the computer. For safety purposes please follow the instructions step by step.

First, shutdown your computer. Then unplug the power cable going into your computer.

Once you have opened the case, touch the metal of the case to discharge any static electricity.

The connector of the PSU which connects to the motherboard is readily recognizable by the number of wires in the bundle. To disconnect it you will need to press on the plastic clip to disengage it and then pull the connector up and away from the motherboard. Please take notice of the location of the locking tab and the notch on the socket of the motherboard, this will only connect one way as it is keyed. This wire bundle will have a memory of the way it has been installed and will want to bend back that direction, you may have to play around with it to find a position that the connector will stay in the same position while you run the test.

Posted Image

From the top left to right the pins are 13-24, the bottom from left to right are 1-12.

Please notice that there are PSUs with 24 pin and 20 pin connectors, the location of the green wire in the 24 pin connector is #16, and the green wire in the 20 pin connector is #14. If you look at the connector with socket side facing you and the clip on the top the number one pin will be on the bottom left corner. This makes the pin out for the 24 pin connector from left to right 13-24 on top, and 1-12 on the bottom. The pin out for the 20 pin connector from left to right is 11-20 on top , and 1-10 on the bottom. If you look at the connectors you notice that these are sockets that fit over the pins on the motherboard where the PSU cable attaches, this is where you will place the jumper. For a jumper you will need a piece of solid wire about the size of a paper clip (20-22 awg), preferably a wire with insulation. It will need to be large enough to fit firmly into the socket so that it will not need to be held in place while testing. You are at risk of electrical shock if you are holding the jumper when you power up the PSU. Insert one end of the jumper into the socket of the Green wire, and insert the other end into the socket of any Black wire.

Once the jumper is in place plug the cord back in. If the PSU is working properly the case fans, optical drives, hdds, and LEDs should power up and remain on. I would suggest that you not leave this connected any longer than is necessary for safety purposes.

To reconnect the 20/4 pin connector unplug the power cord, remove the jumper, and reconnect the connector. Take a moment at this time to make sure that nothing has been dislodged inside the case.
At this point you can use a DC Voltage meter to read the different rail Voltages. You will want to insert the black probe into any of the Black (-) sockets, and insert the Red (+) probe in the five different colored sockets, one at a time. Below are the five different colors and their corresponding rail Voltages. The Voltages should be within about ten percent of the given values.

Yellow +12VDC

Blue -12VDC

Red +5VDC

White -5VDC

Orange +3.3VDC
Posted Image
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#6 Sneakycyber


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Posted 27 December 2008 - 06:55 PM

Sounds like a bad switch. Most computers if you keep the power switch depressed it will force the computer to power down. I would check the switch and make sure its not shorted. Use a DMM (Digital Multimeter) set on continuity and make sure the contacts are only closed when you are depressing the switch.

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#7 gregmallek


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Posted 30 December 2008 - 01:09 PM

So, I decided that my mobo was DOA. After troubleshooting everything I read some reviews of my mobo and other people had the same issues. I decided to return it and get an MSI mobo instead. How is your issue coming along, alpha? You have an Asus mobo, too, have you found that the QC is poor on yours?

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