"iMac LED 1 & 2 are on, chimes but no display"に関する回答Information directly from the source: LED 3 Indicates that computer and video card are communicating. This LED will be ON when computer is communicating properly with video card. If LEDs 1 and 2 are ON and you heard the startup sound, but LED 3 is OFF, then the backup battery (on front of logic board) may need to be reseated, or the video card might be installed incorrectly or needs replacement. LED 4 Indicates that computer and LCD panel are communicating. This LED will be ON when computer is turned on and video signal is being generated. If LED 4 is ON and there is no image on display, then LCD panel, LED backlight board, or cables between LCD and logic board or backlight board might be installed incorrectly, or need replacement.