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Is It My Power Supply?

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3 replies to this topic

#1 Vikeologist


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Posted 16 September 2008 - 08:46 AM


I have an Alienware computer that is a little over 5 years old. Recently i have had problems iwth it booting up, sometimes it would, sometimes it wont.

Yesterday i was on it and it just shut down, then when i went to turn it back on, it wouldnt, then after a little while after waiting, it would turn on, but not boot up and it makes a clicking noise and the light on the motherboard and the lights on the ethernet card fade in and out.

Could this be a powersupply issue or mother board issue? Also, if it is a power supply issue, how do i know which one to order on newegg.com? I know quite a bit about computers, but not real good at doing fixing on them... so please bear with me...

Thanks in advance...

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#2 mobil1_oils


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Posted 16 September 2008 - 09:01 AM

The "clicking" sound suggests to me a moving part. I'd open it up and check all your fans, make sure they are all spinning and nothing is blocking them (Mainly your psu fan and your graphics card). If its not that i would think it may be your hard drive has gone. Open the case, turn it on and listen for where the clicking is coming from.

#3 TheStalker


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Posted 16 September 2008 - 09:14 AM

my frined had an issue once with his computer just turning itself off, turned out the inside needed a really good clean.

#4 Sneakycyber


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Posted 17 September 2008 - 05:51 PM

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.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

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.
Chad Mockensturm 
Network Engineer
Certified CompTia Network +, A +

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