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Motherboard or switch problem?


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6 replies to this topic

#1 DELK

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Posted 17 December 2009 - 05:32 PM

I am having a problem starting my computer. The fans start but then everything shuts down. I am running XP Home and the motherboard is ASUS A7V8X-MX SE. This board has a thermal protection feature which I am told may do just what I am experiencing if the fan is not up to speed. I have cleaned all the fans, but nothing changes. Once the computer boots, after about a dozen or more trys, things work OK. Once the unit is turned off it is uncertain if it will turn on again. Often nothing happens at all when the start button is pushed. Sometimes it will start when the On/Off switch on the back of the computer is toggled, but the start shuts down just as before. It don't suppose this could be a simple thing like a faulty start switch or just replacing the fan on the motherboard? Suggestions?

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#2 Sneakycyber

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Posted 17 December 2009 - 07:51 PM

IT could be a few things, the switch you already mentioned, the motherboard, or the PSU. I would start by testing the switch in the case. First off are you familiar with a multimeter and how they work?
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#3 hamluis

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Posted 17 December 2009 - 07:53 PM

I'd try a different PSU (temporarily) to see if that resolves anything.

Louis

#4 DELK

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Posted 17 December 2009 - 09:54 PM

Sneakycyber: Yes, I have a multimeter.

#5 Sneakycyber

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Posted 18 December 2009 - 10:38 AM

you can test the case switch by using the continuity setting on the meeter or use an OHM setting and it should zero out when the button is pressed. To test the motherboard use a ball point pen or number one philips to short the two pins that the power switch connects two this should turn on the computer. Lastly to test the PSU follow this guide
The purpose of this procedure is to bypass the motherboard to test a ATX PSU. Some manufacturers Like Dell have used some non ATX PSUs which have a different pinout for the 20/4 pin connector, please confirm that your PSU is a ATX type before using this procedure.

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.

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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.
Chad Mockensturm 
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#6 DELK

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Posted 28 December 2009 - 01:00 PM

Happy New Year! I finally got out of the Christmas crazyness and was able to try Sneakycyber's procedures. The case switch was indeed the problem. Although it was not really the switch itself, but the rinkydink, plastic, case-mounted decorative switch pusher that was hanging things up. The switch itself worked fine when pushed directly. Shorting the board pins worked fine, too. I wouldn't have found that out if I weren't following the testing procedures recommended. Thanks for the help. One less annoying thing left behind in 2009.

#7 garmanma

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Posted 28 December 2009 - 06:31 PM

Thank you for posting back and letting us know it's fixed
Mark
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