Apple MD094LL/A Manuale Utente

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

 2010-09-09

Won’t Start Up
•  No startup chime.
•  Error tones during startup.
•  Grey screen with fan noise, or 

other noise.

•  Will not progress beyond 

Apple logo or spinning gear.

1.  Isolate OS by starting up from original install 

media for this computer, from a same-model 

computer in Target Disk Mode, or from a 

compatible known-good OS on an external drive. 

Both AirPort and Bluetooth services are available 

when booted from the Install disk.

2.  Reset SMC and PRAM to clear any stored, 

corrupted information.

3.  Start up in Safe Mode by holding shift key down 

during startup to load only required kernel 

extensions and disable all startup and login 

items. See 

4.  If system generates error tones there may be an 

issue with the SDRAM. See 

5.  Identifying when in the startup process the 

computer hangs can help isolate the issue. 

See 

 for 

information on the Macintosh startup sequence, 

and error codes and symbols used.

6.  Run latest available service utilities.

1.  Boot computer to Apple 

Hardware Test on the internal 

hard drive or an inserted Install 

DVD by holding down the D 

key at startup. Verify if system 

boots up from any of these 

volumes.

Yes

Run the extended tests 

and proceed with results. If 

AHT passes or boots with a 

memory error, go to step 2.

No

Go to step 2.

2.  Remove installed SDRAM, and 

test with known-good SDRAM. 

Verify if computer starts up 

properly now.

Yes

SDRAM issue. Reinstall one 

of user’s SDRAM modules 

and retest. Proceed one by 

one to find the faulty SDRAM 

module, and replace it.

No

Go to step 3.