LED Startup Sequence

LED #1 = Power available.

If no LED is visible:

Verify AC power source

Verify known-good AC cable is connected

Verify cable connection between AC inlet and power supply

Verify cable connection between power supply and logic board

Verify power supply

LED #1 + LED #2 = Power available, and system is powered on.

If second LED is not visible when power button is pressed:

Verify power button connection to logic board

Verify power button functionality

Verify cable connection between power supply and logic board

Verify power supply

Verify logic board

LED #1 + LED #2 + LED #3 = Power available, system is powered on, and video card found.

If third LED is not visible after power on:

Verify that the MXM video card is seated properly

Verify if boot chime is present and fans are running when powered ON (reset SMC and PRAM, check backup battery if necessary for proper boot up):

If POST boot chime is not heard, go to Won’t Start Up symptom flow,

• •

If POST boot chime is heard, go to No Video symptom flow.

LED #1 + LED #2 + LED #3 + LED #4 = Power available, system is powered on, video card found, and internal LCD found.

If fourth LED is not visible after power on:

Verify cable connections between LCD panel and logic board

Inspect LCD display cables for cable damage

Verify external video functionality, and according to result check the following items: -If external display works then verify/replace the LED backlight board

-If external display works then verify/replace the LCD panel

-If external display does not work verify/replace the logic board

2010-09-09

iMac (27-inch, Mid 2010) — General Troubleshooting 31

Page 31
Image 31
Apple MD094LL/A manual LED Startup Sequence, LED #1 = Power available