8 Replies Latest reply: Jan 21, 2013 8:29 AM by Steve Holton
Steve Holton Level 4 Level 4 (1,025 points)

The symptoms:


  1. Running normally, screen goes black
  2. Fans(s) do their 747 takeoff roll imitation
  3. Won't wake up (shouldn't have been sleeping at the point this happened)
  4. Force power off
  5. Attempt re-boot, black screen no sounds except fans take off again after a few seconds


Open it up and find 2 of the 9 red LEDs on the motherboard under lower memory tray are lit up.

Specifically OT1 and OT2 - pretty obviously Over Temp Indicators.

They stay on when power is off, only go out when power plug removed.


If you remove the plug which turns them off, then re-insert they stay off until you power up.

Then the 2 LEDs come on and the fan starts and the 4 LEDs on each memory tray (DIMM1,2,3,4) flash continuously and nothing happens.


There is nothing hot about it.

When it happened was doing normal things - monitoring temps in the recent past  has shown everything to be fine

Let it "cool" for an hours no difference.


In the process I re-seated all the memory - no effect.

I see no dust in any of the visible areas.


One other thing that may be a clue, it has recently occasionally powered itself up spontaneously when turning on the power strip that supplies it.


I can't think of anything that I can do.


Don't suspect the Genius bar has anything to add beyond putting in the shop.


Any thoughts?


If it's the mother board (but no the processors) any idea the magnitude of the cost of replacing the MB??

Mac Pro, OS X Mountain Lion, MacBookAir,MacBook,iPad