Apple MD094LL/A Manuale Utente

iMac (27-inch, Mid 2010) Symptom Charts — Startup and Power 

 2010-09-09

Follow steps in the order indicated below. If an action resolves the issue, retest system to verify.

Unlikely cause: speakers

No Power, Dead Unit
•  No power
•  No fan spin
•  No startup chime
•  No image on external display
•  No hard drive or optical drive 

activity

•  Caps Lock LED on wired 

keyboard doesn’t light when 
pressed.

1.  Verify power source.
2.  Verify power cable.
3.  Listen closely for signs of activity from system 

including: rotating fans, hard drive or optical drive 

activity, startup chime, etc.

1.  Power ON system. Verify if 

there is any indication that the 

system has powered up (fan 

rotation, hard drive or optical 

drive noise, backlight turns on).

Yes

The symptom is powering 

up. Go to 

symptom flow.

No

Go to step 2.

2.  Locate the diagnostic LEDs 

in bottom case vents. Plug 

AC cord into system. Verify if 

diagnostic LED #1 turns ON. 

You may alternately check for 

presence of a 12V DC signal 

between pin 4 and pin 1 of the 

logic board.

Yes

Standby power voltage being 

supplied by power supply. 

Go to step 3.

No

Go to step 4