27" iMac suddenly won't turn on… completely dead?

Discussion in 'iMac' started by shanomurphy, Jan 29, 2016.

  1. shanomurphy, Jan 29, 2016
    Last edited: May 31, 2016

    shanomurphy macrumors newbie


    Jan 29, 2016
    Model: Late 2009 iMac 27" A1312 2309 (Core 2 Duo)

    Need some help please. I woke up one morning recently to find my iMac was dead to any input. It was working fine the night before, I didn't shut down and just let it go to sleep on it's own. There is zero response when the power button is pressed, no boot chime, no screen response, no fans/hard drives spin… nothing.

    What I've tried so far:
    • Different power sockets, different power lead
    • Reset SMC
    • Replaced PRAM battery
    • Replaced iMac power supply
    • Removed graphics card
    There is only one diagnostic led lit on the logic board (labelled LED601) when the iMac is plugged in:


    There are 4 LEDs in total and it's the led furthest from the board edge that lights up. Strangely the service manual for this model seems to list the LEDS in an opposite order to my board:


    I assume the LED that is lit up must be LED 1? ( indicating that trickle voltage from the power supply has been detected by the logic board).

    Does this mean that it's most likely a logic board fail? why would the logic board suddenly fail overnight when iMac was sleeping?
  2. Samuelsan2001 macrumors 604

    Oct 24, 2013
    It's 7 years old and electronics fail with more frequency over time, eventually every piece of electronic equipment will just fail, that's just the nature of the beast. There is a reason most companies won't give more than 3 years warranty and never more than 5 years, and this is it.
  3. shanomurphy, Jan 29, 2016
    Last edited: Jan 29, 2016

    shanomurphy thread starter macrumors newbie


    Jan 29, 2016
    Yeah I understand that… I'm not complaining, I'm just trying to diagnose what component has failed.

    I'm thinking it must be the logic board unless anyone else can offer some suggestions? I've actually sourced a used logic board from a 2009 core i5 iMac complete with CPU so I'm going to see if I can resurrect it with that. If it works it should also be a nice performance boost too compared to the Core 2 Duo it currently has. Heck if it works I could even potentially stick a 2011 model i7 cpu in there to really extend it's life some more! It is already a bit of a frankenstein as it has a 2011 GPU (6770M) and SSD :)

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