Apple MD094LL/A Manuale Utente

iMac (27-inch, Mid 2010) Symptom Charts — Display 

 2010-09-09

Unlikely cause: hard drive, optical drive, speakers, camera, microphone

Backlight Issue/No Backlight
•  No image
•  Partial backlight failure
•  Backlight flickers
•  Display dim

1.  Check for Software Update.
2.  Verify that System Preferences > Displays > 

Brightness control setting is above minimum.

3.  If no image on built-in display, connect external 

display to verify if iMac video circuitry is 

functioning. If no image visible on external 

display, go to 

 symptom flow under 

Startup and Power troubleshooting.

1.  Verify boot chime present and 

fans running when computer 

powered ON. (Reset SMC, clear 

PRAM or reseat Backup Battery 

if necessary for proper boot 

up.)

Yes

Power on self test OK.  

Go to step 2.

No

Go to 

 

symptom flow.

2.  Verify if image is visible on 

built-in LCD panel, with 

adjustable backlight level.

Yes

Video is present. Verify system 

functionality and return to 

user, or go to appropriate 

troubleshooting flow.

No

Go to step 3.

3.  Connect supported external 

display to rear Mini DisplayPort 

video port (Use known-good 

MiniDisplay to VGA or DVI 

adapters if needed) . Verify if 

image appears on external 

display when system is booted.

Yes

External display detected 

by system. Video circuitry 

on logic board appears 

functional.  Go to step 4.

No

Go to 

 symptom 

flow.

4.  Verify if LCD backlight is ON 

by looking for faint glow 

from display when viewed in 

darkened room with brightness 

set at maximum.

Yes

LED backlight is functioning. 

Go to step 7.

No

Go to step 5.