The diagnostic LEDs are located to in a column next to the memory slot. Please see the image below.
LED 1 : Trickle power from the power supply to main logic board.
LED 2: Main logic board has detected trickle power from the power supply when the unit is powered on.
LED 3: Computer and video card are communicating with each other.
LED 4: Computer and LCD panel are communicating with each other.
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Diagnosed off your site ; bought new power supply from you , ( US to Australia in 6 days ) ; swapped it in ; pushed the ram in really hard ; booted up and awaaaay we go . Thank you very much . Even us older folks can follow your excellent guides . Your help was invaluable and I hope to spend lots more time on my trusty old Mac .
crwdns2934271:0crwdnd2934271:0 geoff ellis crwdne2934271:0