Apple imac 17in 1ghz Service Manual

16 - iMac (17-inch Flat Panel, 1GHz) Troubleshoot-

No Video Symptom Charts

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 on the bottom of the computer. With the unit powered on, check if a red 

LED is visible in the access door. If the red LED is on, power is on. If you don’t see the LED glowing 

red, follow the steps under the symptom “No Power”. 

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. If you don’t have external 

video, replace the main logic board. If you do have external video, go on to the next step.

6.

Open the bottom housing and verify that all the cables are securely attached. Pay special attention to 

the video cable (located near the modem). If the cables are securely attached, go on to the next step. 

Warning:  Whenever the bottom housing is opened for service, you must do two things:

• You must clean the original thermal film from the surfaces joining the thermal interface layer and 

reapply thermal paste to the thermal pipe.

• The bottom housing has four torx screws that must be tightened to at least 17 in.-lbs. If you do not 

have a torque driver, you will have to make sure these screws are tightened by hand FIRMLY, BUT 

NOT FORCIBLY. Or, purchase the service tool (076-0899) in order to ensure the thermal pipe is 

firmly mated with the top base. If the bottom housing is not securely attached to the base in this 

fashion, the CPU may overheat and become damaged.

7.

Check the connection of the video cable to the LCD flat panel display (under black tape). 

8.

Replace the inverter board.

9.

Replace the LCD display. Important: If you are replacing the display, be sure to install the new display 

shield and EMI gaskets that come with the new LCD panel. Installation instructions are included with 

the new display panel. Additional display shields/gasket kits are also available separately as a kit, part 

#076-0958.

10. Replace the neck assembly

11. Replace the logic board. 

12. Replace the power supply board.