An improper shutdown while the monitor is set to an incompatible resolution or scan rate could cause a lack of video at system startup time.

Symptom

The monitor does not display any video when the computer is turned on, or displays a video image briefly at but then goes blank part way through the startup process. An alert box may appear with a message about the monitor's sync rate or resolution.

Products affected

• Mac OS 9
• Power Macintosh G3 (all models)
• Power Mac G4 (all models)
• iMac (all models)

Solution

The system is attempting to use an incompatible display resolution or scan rate. Follow these steps to restore the monitor:

1. Reset the computer's parameter RAM (PRAM). For information on resetting PRAM, please see article 2238: " Macintosh: How To Reset PRAM and NVRAM "

2. Start up the computer with extensions off. To do this, hold down the Shift key when you turn on the computer until the message, "Extensions Off" appears.

3. After the desktop appears, drag these items from the Preferences folder (within the System Folder) to the Trash:

• Display Preferences file
• Monitor Preferences folder
• preferences file for third-party resolution switching software, if installed

4. Restart the computer.

5. Set up the monitor's resolution as desired.

Note: If you have more than one hard disk or partition, the computer may start up using a different System Folder than the one in use when the issue occurred. If so, be sure to remove the Display Preferences and Monitor Preferences from the System Folder that was in use when you experienced the issue.

Background

This behavior may have immediately followed a forced restart or other improper shutdown while the monitor was using an incompatible resolution or scan rate. An incompatible resolution is one that does not appear in the Monitors control panel.

There are several ways an incompatible resolution or scan rate can be set. Certain games change the resolution and/or scan rate when loading, and some utilities allow display resolutions to be selected that are not available in the Monitors control panel.