HT2173: iMac G5: Troubleshooting when your computer won't turn on

Learn about iMac G5: Troubleshooting when your computer won't turn on
ryan haid
Level 2 (175 points)

Q: iMac still won't start after logic board replacement

Hi,

 

My iMac G5 stopped starting up recently. On the diagnostic LEDs, only the first one came on (even after resetting teh SMU) so I replaced the logic board. However, I'm stuck with the same problem on the new logic board. Any ideas on what else could be causing this problem? All of the capacitors look fine on the new board and I was told it was pulled from a working machine.

iMac G5, Mac OS X (10.3.7)

Posted on Mar 9, 2013 3:59 PM

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ryan haid

Q: iMac still won't start after logic board replacement

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  • by rccharles,

    rccharles rccharles Mar 10, 2013 6:31 PM in response to ryan haid
    Level 6 (8,476 points)
    Classic Mac OS
    Mar 10, 2013 6:31 PM in response to ryan haid

    http://support.apple.com/kb/ht2831

    states that:

    1. Locate the large white arrow in the middle of the computer. Above this arrow, you'll see four LEDs:
      • LED 1 indicates that trickle voltage from the power supply has been detected. This LED will be ON when the computer is turned off and your power supply is working correctly.
      • LED 2 indicates that the main logic board has detected proper power from the power supply when the computer is turned on. This LED will be ON when the computer is turned on and the power supply is working correctly.
      • LED 3 indicates that the computer and the LCD display are communicating. This LED will be ON when the computer is turned on and video signal is being generated.
      • LED 4 lights only if the computer detects an over-temperature condition. This LED will be OFF when the computer is turned on and running at the correct temperature.

                 These diagnostic LEDs can be used to help you troubleshoot your computer.

     

    Seems that led 2 meains power supply or logic board or something else.

     

    I'd disconnect hd & dvd drive & see of you get more lights.

     

     

    I've read where there have been reports of bad capacitors in power supply. 

    You may be able to look at the capacitors & see if they are buldging.

    http://www.jwestsales.com/products/B-PSU-Apple-G5-iMac-Power-Supply-Capacitors-K it-B-Style.html

    http://www.ifixmaccomputers.com/psu-capacitor-kit-repair