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Computer won't turn on... Possible cuases?

Posted on 2006-11-01
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Last Modified: 2010-04-25
I have an older computer that I was doing some maintainence on.  After installing a new hard drive, memory, and a graphics card, I tried to turn the computer on and nothing happens.  I figured it was the power supply so I put a new one in, and it still doesn't work.  I checked the power connections from the power supply to the mother board, they are tight.  I checked the connector that connects the power button on the case to the mother board, it is also tight.  What are some other possible causes that would lead to the computer not turning on at all?
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Question by:josephdaviskcrm
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phototropic earned 250 total points
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Faulty power switch?  Disconnect the power switch from the mobo headers and short the terminals with a small screwdriver.  Does it power up?  If so, the switch mechanism is faulty...

"...I tried to turn the computer on and nothing happens..."  No LED on the mobo? No fans spinning in the PSU?  Try another wall outlet/mains cable...

If the PSU and mains lead are known good, what about the RAM you upgraded to...are you sure it is compatible with your mobo?   Try removing it and replacing the RAM you had originally, if it is still around...does the pc power up now?  If it does, the RAM is incompatible...

Try removing the RAM and disconnecting everything except the molex power connector ... anything happening?  Any beeps, fans spinning?
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by:josephdaviskcrm
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ok I tried shorting out the power pins on the mother board, nothing happend.  I tried using a different power cable from the wall socket to the power supply, nothing happend.  I tried removing the RAM and starting the computer, nothing happened.  I don't understand what the molex power connector is.
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by:phototropic
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Big white plastic 20 (or 24) pin power connector from the PSU to the motherboard.  Is there also a socket for a small 4-pin molex connector on your board?  If it is an old board there probabley isn't, but if there is, you need to connect that as well in order to power up the pc.

If there is no 4 pin connector and none of the above has any effect, you would have to suspect the motherboard...

You might try replacing all the components you upgraded with the original pieces of hardware and see if the pc powers up then.  If not, the mobo and/or CPU are prime suspects...
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by:simpswr
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. . and check to see if the power supply has a switch on the back . . and that it is on
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by:josephdaviskcrm
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Ok... we are going to assume that the mother board is the problem.  I stripped all the parts out of the old computer and and put them into another machine of the same age and make.  Upon powering on the system, everything seems to turn on, but the monitor stays black.  It is as though the computer doesn't know that the monitor is there.  I have double checked the tightness of the cords of the monitor plugged into the serial port.  I have switched monitors and I have traded out the graphics card for another one.  Nothing seems to work.  Do you have any ideas about this one?
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by:drypz
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Check if it is grounded. Remove your motherboard from the casing and try to connect all the components.
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by:bgbeer
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ram could also cause this.

get the the of the mobo and go to www.crucial.com and see if you bought the right ram for the mobo.
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by:PCBONEZ
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It sounds like your video card may be the wrong AGP version for the motherboard.

http://www.abcd.com.au/v/agp_slot.htm

http://www.interfacebus.com/Design_Connector_AGP.html
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