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iMac starts with fan, screen stays black

When attempting to start my iMac G5 (Ambient Light Sensor), fans come on but screen stays black. A couple minutes later, the fans rev up and run very quickly and loudly. This started happening when:

1. One day the screen showed a green question mark with a message indicating that the computer needed to be restarted in a box
2. Green lines were all across the screen
3. I forced it to shut down by holding down the power button
4. When I attempted to start it back up the fans started but the screen stayed black
5. After a couple of minutes, the fans revved up

This has been happening ever since. One time the computer started to the desktop but everything was frozen. I have reset the PMU, checked the diagnostic LEDs, reset the PRAM-basically everything suggested. Can anyone help? Thanks!

iMac G5 (Ambient Light Sensor), Mac OS X (10.4)

Posted on Apr 7, 2009 9:36 AM

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Posted on Apr 7, 2009 10:02 AM

Try the suggestions mentioned in the following Articles:

http://docs.info.apple.com/article.html?artnum=301283 Troubleshooting when there's no picture on the display

http://docs.info.apple.com/article.html?artnum=301733 iMac G5: How to Reset the SMU (iMac G5, the iMac G5 (Ambient Light Sensor), and the iMac G5 (iSight)).


Strongly recommend that you update to OS 10.4.11. Your system info confirms you are still using the basic Tiger OS.
3 replies
Question marked as Best reply

Apr 7, 2009 10:02 AM in response to realchemist

Try the suggestions mentioned in the following Articles:

http://docs.info.apple.com/article.html?artnum=301283 Troubleshooting when there's no picture on the display

http://docs.info.apple.com/article.html?artnum=301733 iMac G5: How to Reset the SMU (iMac G5, the iMac G5 (Ambient Light Sensor), and the iMac G5 (iSight)).


Strongly recommend that you update to OS 10.4.11. Your system info confirms you are still using the basic Tiger OS.

iMac starts with fan, screen stays black

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