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Power supply or power button problem?

Discussion in 'Hardware' started by Kendall1408, Jul 28, 2009.

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  1. Kendall1408

    Kendall1408 Thread Starter

    Joined:
    Jan 19, 2009
    Messages:
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    Hi everybody,

    I tried to search on google about this, but it's not really help and it never happen to me before so I post here.

    My PC was running normally for a long time, just couple weeks ago I sent my faulty video card (xfx nvidia 8800 ultra) to get warranty service and they sent me back another. The new one works fine, but a week later I tried to turn on my computer and there's no power at all. No lights on, no fan running, just no sign of power. So I check inside if there's any wire from the PSU is unplugged, but everything looks good, nothing seems wrong. I'm sure the power from the wall is good and the power switch on the back is on. So I tried to check the wired again, push the power cable to the mother harder and press the button, it worked. But that doesnt solve the problem, if I put something heavy near the PC or the desk is vibrating a little bit, the power turns off. I press the power button again it would not turn on until I open the case and press the power cable to the motherboard harder, it's on. I then close the side panel, it's off, no power.
    This is really annoyed me, I dont know what else to do. What caused this problem? The power supply or the power button? Can somebody help me?

    My system specs:
    ECS G31T-M mobo, Intel E8400 Duo, 2x2GB RAM
    2x2 SATA HD, nVidia 8800 ultra video card
    ULTRA's 1000watt PSU
     
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  3. JPCompHelp

    JPCompHelp

    Joined:
    Jul 27, 2009
    Messages:
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    Sounds like a loose cable. Replace it if you can, otherwise you're going to have to buy another PSU.
     
  4. Kendall1408

    Kendall1408 Thread Starter

    Joined:
    Jan 19, 2009
    Messages:
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    That cable is not loose, I found it fit perfectly to the jumper and very hard to take out :(
     
  5. JPCompHelp

    JPCompHelp

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    Jul 27, 2009
    Messages:
    311
    Then it might be a problem with the PSU. Try replacing it with another one and see if that helps.
     
  6. win2kpro

    win2kpro

    Joined:
    Jul 19, 2005
    Messages:
    11,670
    Is your power supply a modular unit? If the power supply is modular or hard wired, check all the connectors for signs or an "arcing" connection. Be sure and check the 24 pin connector that connects to the motherboard. You will need a bright light and a magnifying glass to check the female connections. If a main plug connector is "arcing" you can generally see it on the male pins in the mainboard connector socket. There will normally be black or blue marks on the pins if a connection is "arcing".

    Check your mounting screws that attach the motherboard to the chassis standoffs and make sure they are not too tight. They should be "snug" but not over tightened.

    ECS is a poor quality board, and you may have a defective solder connection on the board circuitry. You won't be able to see the defective solder joint, but you can apply downward pressure on various parts of the board to see if it causes the board to "cut off".

    Power on switchs very seldom fail since they are so simple. They are just a normally open switch that makes contact when the switch is depressed.
     
  7. Kendall1408

    Kendall1408 Thread Starter

    Joined:
    Jan 19, 2009
    Messages:
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    Yes, my PSU is a modular unit. I checked and I'm sure there's no "arcing" problem. I have an ASUS P5QC mobo and it had the exact problem like this when I install the video card after warranty, that's why I switch to my old ECS one and it worked for a while until now.
    I noticed that after I press the power cable again, the PC works and and the screen would show: " CMOS Checksum Bad. CMOS Date/Time not set". I dont get this, I never reset CMOS or take out the battery on the mobo. And what about the defective solder connection you said? How do I fix it?
     
  8. win2kpro

    win2kpro

    Joined:
    Jul 19, 2005
    Messages:
    11,670
    #1-When troubleshooting a problem like this start at the beginning. If you have a power supply tester, test the power supply, if you don't have a tester take the tower in to a facility that has a tester and have them test the unit. Also, have them "jump" a known good power supply to the board and see if the problem continues.

    If the problem is in the mainboard plug, in the past I have had to remove the female molex pins from the plug and check each individually for a bad crimp. If you have a bad
    solder connection on the board socket you may be able to see it with a magnifying light by removing the board and checking each connection at the socket.

    #2-Replace the battery, access BIOS and reset the time.

    #3-Trying to find a defective joint in a PCB is an exercise in futility. Just turn the board over and look at all the printed circuits. You could spend days trying to find a defective circuit on a PCB. If you isolate the problem to defective board circuitry, in most cases it is not economically feasible to try to repair the board.

    Problems such as you are encountering are one reason I personally don't care for modular power supply's. With any electrical circuit when you put a "break" in the circuit such as a plug or a socket, you have twice as many points of potential failure than with a hard wired circuit.

    Since you have changes that occur when you plug the power supply plug into the board socket, then obviously this is the point to start looking for your problem. Since starting and stopping a board is controlled by the +5v circuit (red wires, gray wire and purple wire on the connector) they deserve close inspection for bad connections.

    You can test the power on button as being the problem simply by disconnecting the kk connectors for the power on button and using a flat bladed screwdriver to momentarily "short" the front panel power on pins to start the machine, leave the kk connector disconnected and see if the problem continues. If the problem continues with the power on kk connector disconnected from the frant panel header, then the problem is not in the power on switch.
     
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