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Faulty psu ?


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#1 kennyboy3

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Posted 01 September 2010 - 01:10 PM

I have a self built system that has been running with no problems for over a year but now has develpoed a curious fault, sometimes it will not boot up but the fans all run but no keyboard lights flash and no signal to the monitor no beeps etc , but if I power down manually and disconnect the power lead and hold the power on button in for about a minute then reconnect the power lead it will then proceed to boot up as normal not always but most of the time , sometimes takes a couple attempts but i can usually get it too boot up this way , could anybody tell me why this is and how can I rectify this problem as it is a pain having to do this in order to make it boot up , many thanks in advance for any advice on this Cheers :thumbsup:

Edited by hamluis, 01 September 2010 - 08:34 PM.
Moved from Vista forum to Internal Hardware ~ Hamluis.


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#2 MrBruce1959

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Posted 01 September 2010 - 10:57 PM

Hello and welcome to Bleepingcomputer.

Since it takes unplugging the PSU to get the computer to boot up, this sounds to me like a possible fault in the PSU.

It could also be a faulty connection on one of the wiring harnesses coming from the PSU to the motherboard.

First try disconnecting the wire harnesses coming from the PSU to the motherboard and reconnecting them, sometimes this resolves an oxidation build up that happens when two metals are pressure connected rather than being soldered together.

Try booting up the computer again, problem will either be solved or it won't.

Try re-seating your video card and RAM sticks and try booting again.

If problem is not solved, you have a controller problem in your PSU, I do not advise anyone to attempt to service the inside of the PSU since it contains electrolytic capacitors which can store lethal amounts of current, long after the power has been cut off and severe burns or electric shock can be the result of playing around inside a PSU.

If your PSU is faulty, either replace it or have it serviced by a qualified repair shop.

Bruce.

Edited by MrBruce1959, 01 September 2010 - 10:58 PM.

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#3 dc3

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Posted 02 September 2010 - 01:47 AM

Testing PSU

The purpose of this procedure is to bypass the motherboard to test the PSU.

Caution:
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.


Addition to testing PSU by jumper. Reading rail voltages with DC Voltage meter.

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 plus or minus of the given values.

Yellow +12VDC

Blue -12VDC

Red +5VDC

White -5VDC

Orange +3.3VDC

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#4 kennyboy3

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Posted 02 September 2010 - 04:42 PM

Thank you for your replies due to work I wont be able to try out your suggestions till this sunday , will try the connections first then onto testing the psu if the that doesnt cure the problem , I will let you know the outcome , thanks again :thumbsup:

#5 kennyboy3

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Posted 05 September 2010 - 07:52 AM

:flowers: thanks for the help mrbruce and dc3 looks like oxidation was the the culprit after diconnecting and reconnecting all the power leads all is fine , panic over , as a matter of interest is there any type of spray or anything to use when assembling the connectors to aid conduction ? :thumbsup:

#6 Layback Bear

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Posted 05 September 2010 - 09:24 AM

Good mourning, you could use
DeoxIT® D-Series - Contact Cleaner & Rejuvenator.

#7 MrBruce1959

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Posted 05 September 2010 - 12:29 PM

I am happy to hear that as a team, we were all able to be of assistance to you and that your problem has been resolved. :flowers:

Happy computing! :thumbsup:

Bruce.

Edited by MrBruce1959, 05 September 2010 - 12:30 PM.

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#8 kennyboy3

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Posted 08 September 2010 - 06:39 AM

Hi layback sorry for the late reply , thanks for the tip on the contact cleaner will try and get some to keep around the house , Cheers :thumbsup:




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