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Intel-based Mac computers such as the iMac rely on a combination of tones to indicate 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 incorrect type of RAM, 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 tones until computer is turned off. • The solution to both of these situations is to first re-seat memory and test computer again. If memory fails POST again, remove all installed memory and test by installing one by one each memory module 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

The System Management Controller (SMC) is a chip on logic board that controls all power functions. If computer is experiencing any power issue, such as not starting up, not displaying video, sleep issues, or fan noise issues, resetting SMC may resolve it. To reset SMC on an iMac: 1. From Apple menu, choose Shut Down (or if the computer is not responding, hold power button for approximately ten seconds until it powers off). 2. Unplug all cables from computer, including power cord. 3. Press and hold the power button for 5 seconds. 4. Release the power button. 5. Attach the computer’s power cable, making sure power button is not being pressed. Note: If you press the power button while inserting the power cord, the iMac will enter a mode in which the fans run at full speed. 6. Press the power button to turn on the computer.

PRAM stores certain system and device settings in a location that Mac OS X can access quickly. Exactly which settings are stored in the computer’s PRAM varies depending on the type of computer as well as the types of devices and drives connected. To reset PRAM: 1. Shut down the computer. 2. Locate the following keys on keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in Step 4. Note: If the keyboard does not have an Option key, use the Alt key instead. 3. Press power button. 4. Immediately press and hold Command-Option-P-R keys. Important: You must press this key combination before the gray screen appears. 5. Hold down keys until the computer restarts, and you hear the startup chime a second time. 6. Release keys. if you still have problems call us +1-855-517-2433

LED #1 = Power available. If no LED is visible: • Verify AC source • Verify known-good AC cable is connected • Verify cable connection between AC inlet and power supply • Verify cable connection between power supply and logic board • Verify power supply LED #1 + LED #2 = Power available, and system is powered on. If second LED is not visible when power button is pressed: • Verify power button connection to logic board • Verify power button functionality • Verify cable connection between power supply and logic board • Verify power supply • Verify logic board LED #1 + LED #2 + LED #3 = Power available, system is powered on, and video card found . If third LED is not visible after power on: • Verify that MXM video card is seated properly • Verify logic board LED #1 + LED #2 + LED #3 + LED #4 = Power available, system is powered on, video card found, and internal LCD found. If fourth LED is not visible after power on: • Verify cable connections between LCD pane