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weird power issue...wont turn on after sitting


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#1 chickenpick

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Posted 07 June 2010 - 04:19 PM

my computer quit turning on. Thinking it was the power supply I switched the mobo into a box i had with a nice new ps. It fired right up. And if I restart it it will do that. The problem is that it will not start up after being off for awhile. So I open the side and just brush the edge of the mobo by where the power switch etc. jumpers are, and it comes on. This happens every time. Also the CMOS acts like the battery is dead as I have to reset the time and date after this event. Alls good if I leave it running but....Do you have any idea what this is? A dead CMOS shouldnt prevent the unit from powering up should it?

Edited by chickenpick, 07 June 2010 - 04:36 PM.


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#2 Sneakycyber

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Posted 08 June 2010 - 08:13 PM

IF you have to reset the date and time the battery is dead or there is a problem with the motherboard. Change the battery and see if it boots normally. If it still doesn't work I would suspect a faulty on/off switch. You can test it with a DMM (digital multimeter)

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#3 chickenpick

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Posted 08 June 2010 - 11:12 PM

Ill try the battery...always happens when im dirt broke lol...Will the dead battery cause the nonstart? And what about the light touch to the mobo thing? and the switch is new with the case.

#4 Sneakycyber

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Posted 09 June 2010 - 09:17 AM

The battery should be relatively cheap check the couch cushions :thumbsup: As for the light touch to the MB could be static shock to the MB causing it to wake up.

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#5 chickenpick

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Posted 10 June 2010 - 11:18 AM

i will try that..thanks.

#6 chickenpick

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Posted 14 June 2010 - 05:24 AM

New battery....redid all connections...same story...What is going on? Resets ok, but if it sits a couple hours, no start

#7 Sneakycyber

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Posted 14 June 2010 - 09:51 AM

Test the power supply. 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.

Posted Image
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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.

At this point you can use a DC Voltmeter 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

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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#8 chickenpick

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Posted 14 June 2010 - 11:09 AM

ill try...its a brand new 500w ps

#9 Sneakycyber

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Posted 14 June 2010 - 07:28 PM

If its not the PSU I would have to suspect the motherboard then.

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#10 caperdog

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Posted 14 June 2010 - 08:12 PM

or like you said earlier Sneakycyber it could be the switch. you can bypass the switch by unplugging it from the motherboard and shorting the two motherboard pins with a screwdriver. just touch for a second and remove. computer should start.

#11 chickenpick

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Posted 15 June 2010 - 08:40 AM

remember it always turns on when jumped....switch always works hot. Cold starts are the problem

#12 caperdog

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Posted 15 June 2010 - 12:30 PM

what does "So I open the side and just brush the edge of the mobo by where the power switch..." mean ? with your finger ?
if so unplug the switch and try it with a metal conductor (i.e. screwdriver) when machine is "cold".




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