Справочник Пользователя для Apple MD094LL/A

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

2010-09-09

For information on how to isolate a hardware issue from a software issue, refer to: 

For information on how to troubleshoot a software issue, refer to: 

kBase #HT1199: Mac OS X: How to troubleshoot a software issue 
kBase #TS1394: Mac OS X: Troubleshooting installation and software updates 
kBase #HT2956: Troubleshooting Mac OS X installation from CD or DVD

Intel-based Mac computers such as the iMac rely on a combination of tones and blinking LEDs 
to display Power On Self Test (POST) error codes.
•  If the computer detects out-of-specification or no SDRAM, the screen will remain black 

but the computer will beep. This error condition may be due to physically damaged RAM, 
installing the incorrect type of RAM, poor connection, or not having RAM installed.

•  Some RAM may appear to pass the Power-On-Self-Test (POST) but still cannot be used by 

the operating system. In this case, the computer will display a gray screen, sound three 
tones and repeat the tones until the computer is turned off. 

•  The solution to both of these situations is to first re-seat the memory and test the 

computer again. If the memory fails the POST test again, remove all installed memory and  
test by installing one by one each memory that has been verified to work correctly on 
another system (i.e., “known-good”) or order new memory.

•  A sequence of tones heard at startup or a no video symptom may also be fixed by 

temporarily removing/replacing the backup battery.