User Guide

iMac (27-inch, Late 2009) Symptom Charts — Startup and Power 39
2009-12-16
Pivot enclosure to access 4.
lower intake vent, and locate
diagnostic LEDs on edge of
logic board. Verify if LED #3
turns on shortly after system
powers on.
Yes Logic board communicating
with video card. Go to step 5.
No If LED #3 does not turn ON
reseat video card and retest,
then replace video card and
repeat step 4. If issue persists,
replace logic board.
M03
Locate 5. diagnostic LEDs on
logic board. Verify if LED #4
turns on shortly after system
powers on.
Yes Logic board communicating
with LCD panel. Go to
Backlight Issue/No Backlight
symptom ow.
No Replace DisplayPort cable. Go
to step 6.
Locate 6. diagnostic LEDs on
the logic board. Verify if LED #4
turns on shortly after system
powers on.
Yes Video controller functional
and communicating with LCD
panel. Go to Backlight Issue/
No Backlight symptom ow.
No Video controller unable to
communicate with LCD panel.
Reseat cables rst. If issue
persists, replace LCD panel.
Retest.
M03