This answer is basically for the G5 machine. Will do better when we know your exact machine.
Pop the back off. Note the two CUDA buttons the logic board. On is a reset and one a power on.
Hit both with the machine plugged in. Observe the diagnostic lights in the center of the board and tell us what you see. Also examine the 24 "cans" capacitors for swelling, and/or leakage.
'''UPDATE for intel model'''
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There are possibly diagnostic LEDs to the right of the RAM slots (sometimes they can covered by a small piece of black tape that may need to be removed). Please tell us if your have them and what they are showing.
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LED 1 - Indicates that the trickle voltage from the power supply is detected by the main logic board. This LED will remain ON while the iMac is connected to the AC power. The LED will remain on even when the computer has been shut down or put to sleep. The LED will turn off only if the AC power is disconnected or the power supply is faulty.
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LED 2 - Indicates that the main logic board has detected proper power from the power supply when the computer is turned on. This LED will be ON when the computer is turned on and the power supply is working correctly.
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LED 3 - Indicates that the computer and the video card are communicating. This LED will be ON when the computer is communicating properly with the video card. If LEDs 1 and 2 are ON and you heard the startup sound, but LED 3 is OFF, then the video card might be installed incorrectly or need replacement.
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LED 4 - Indicates that the computer and the LCD display panel are communicating. This LED will be ON when the computer is turned on and video signal is being generated. If the LED is ON and there is no image on the LCD display panel, the LCD display panel or inverter might be installed incorrectly or need replacement.
This answer is basically for the G5 machine. Will do better when we know your exact machine.
+
Pop the back off. Note the two CUDA buttons the logic board. On is a reset and one a power on.
Hit both with the machine plugged in. Observe the diagnostic lights in the center of the board and tell us what you see. Also examine the 24 "cans" capacitors for swelling, and/or leakage.
+
+
'''UPDATE for intel model'''
+
There are possibly diagnostic LEDs to the right of the RAM slots (sometimes they can covered by a small piece of black tape that may need to be removed). Please tell us if your have them and what they are showing.
This answer is basically for the G5 machine. Will do better when we know your exact machine.
Pop the back off. Note the two CUDA buttons the logic board. On is a reset and one a power on.
Hit both with the machine plugged in. Observe the diagnostic lights in the center of the board and tell us what you see. Also examine the 24 "cans" capacitors for swelling, and/or leakage.
Pop the back off. Note the two CUDA buttons the logic board. On is a reset and one a power on.
Hit both with the machine plugged in. Observe the diagnostic lights in the center of the board and tell us what you see. Also examine the 24 "cans" capacitors for swelling, and/or leakage.