boot up problem with I mac

the mac starts to boot up and then goes to restart screen can't seem to get past that. It did allow me to reload software os but wont boot on its own. the led lights on the logic board only light to 3 4th one dose not come on. I've been told the mother board is out. I have not had any problem the 5 years I've had this imac. any ideas?

thanks Stephen

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Be glad that the 4th light did not come on. Here's what they mean:

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.

If the machine will boot from the DVD, then it's most likely a hard drive failure. Boot from the DVD, go to the second screen pull down menu, Utilities, Disk Utility and try to run the "Repair". That failing, reformat the drive using the "write zero's" option, this will eliminate any bad blocks. Now try reinstalling the system. This failing, replace the hard drive. Here's how: iMac G5 17" Model A1058 Hard Drive Replacement

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Hi Mayer I did replace the hard drive and I tried to install the software. It gets to the point were the computer wants to restart and stops at the restart screen still. Could the cables be bad to the hard drive?

What else can I do? l.e.d.'s 1,2,3, come on just fine. I look forward to hearing from you. Stephen

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Boot from the optical drive by inserting the system installation disk and holding down the "C" key.


Mayer, I just wanted to let you know after I replaced the hard drive I still had the problem so I started looking at the optical drive. I replaced it and reloaded the software . Everything came back up. I'm using the G5. I wanted to Thank You for your assistance. Have a great day.


Thanks for letting me know, it's all the pay most of us get. If you would please Accept the answer os that it can help others with similar problems.


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Stephen will be eternally grateful.
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