Specifications

No Video
The screen is dark, fan and hard drive are spinning.
1. Reset parameter RAM. Press Command-Option-P-R during startup before “Welcome to Macintosh”
appears.
2. The system software could be damaged. Start up from the system CD that came with the computer.
3. Remove the user access panel. With the unit powered on, check if a red LED (shown below) is visible in
the access door. If the red LED is on, power is on. If you don’t see the red LED glowing red, follow the
steps under the “No Power” symptom.
4. Disconnect the A/C power cord. Place the unit in the service stand and remove the user access plate.
Press the PMU reset button on the logic board. Refer to “Resetting the PMU on the Logic Board”
mentioned earlier in this chapter.
5. Check for external video. Connect an external monitor to the mini-VGA port using an Apple VGA Display
Adapter, part # M8639G/A. Make sure your monitor supports the following resolutions and refresh rates:
• 640 x 480 @ 60 Hz
• 800 x 600 @ 75 Hz
• 1024 x 768 @ 75 Hz
If the unit has external video, the video chip on the logic board is putting out a good signal. Go on to
step 6. If there is no external video, but the unit appears to be operating normally otherwise, replace the
logic board.
6. Open the bottom housing and verify that all the cables are securely attached to the logic board. Pay
special attention to the video cable connector (located near the modem). Reconnect cables and try
again.
7. Recheck all the connections to the panel before replacing the panel. Pay special attention to the flat
video cable connection (under copper tape) going into the LCD panel.
No Video Symptom Charts
iMac (Flat Panel) Troubleshooting - 17